Click to see all the text

In collaboration with the Barry Group in Corner Brook, a larval survey was conducted from 15-17 July 2004 between Bonne Bay and Port-au-Port Bay on the west coast of Newfoundland. The survey’s main objective was to describe the fish egg and larva distribution from this area and measure the larva abundance of commercial species including capelin (Mallotus villosus) and Atlantic herring (Clupea harengus). During the survey, the eggs from three species and three groups of species were identified as well as the larvae from 20 species, including capelin, cunner (Tautogolabrus adspersus), Atlantic herring, flounder (Pleuronectidae spp.), Atlantic cod (Gadus morhua) and Atlantic mackerel (Scomber scombrus L.). The average abundance of capelin larvae was estimated by kriging to be 694 larvae / 1,000 m³ compared with 211 larvae / 1,000 m³ for Atlantic herring. Various biodiversity measurements indicate that the larval community structure was characterized at the time of the survey by the occurrence of a large number of scarce species and by commercial species concentrated in different areas. Cluster and ordination analyses applied to the Bray-Curtis similarity index helped establish groups of stations characterized by the occurrence and abundance of certain species in particular. Significant differences in average temperature and salinity were recorded between these groups. However, these differences aren’t large enough to show a link between the specific larval composition at each group of stations and these two environmental variables.

LAMBREY DE SOUZA, J., J.-M. SÉVIGNY, J.-P. CHANUT, W.F. BARRY, F. GRÉGOIRE, 2006. High genetic variability in the mtDNA control region of a northwestern Atlantic teleost, Scomber scombrus L. Can. Tech. Rep. Fish. Aquat. Sci., 2625, 25 p .

Click to see all the text

The left branch of the mtDNA control region was sequenced for 76 Atlantic mackerel (Scomber scombrus L.) sampled in the Gulf of St. Lawrence, the Gulf of Maine and off the North Carolina coast in an attempt to determine if the northern and southern populations of this species are genetically differentiated. Sequencing has revealed that the mtDNA control region is highly variable in this species. Indeed, 48 haplotypes were observed in the 76 individuals analyzed, and haplotype diversity values varied from 0.982 in the Gulf of Maine to 0.992 in the Gulf of St.Lawrence. The results of the AMOVA and of the phylogenetic analyses did not reveal differences between the northern and the southern populations. The results of the present study suggest that, if homing is a feature of the reproductive behaviour of the Atlantic mackerel, straying appears to be high enough to prevent genetic divergence between the two populations in the Northwest Atlantic. However, the very high variability of the studied mtDNA fragment and the small sample size used may have prevented the detection of genetic organization of the species.

GRÉGOIRE, F., 2006. Distribution verticale des captures de maquereau bleu (Scomber scombrus L.) au chalut pélagique en relation avec la température de l'eau ; Vertical distribution of the midwater trawl catches of Atlantic mackerel (Scomber scombrus L.) in relation with water temperature. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2006/097, 44 p .

Click to see all the text

The edge of the Scotian Shelf is characterized by a layer of deep water whose winter and spring temperatures are higher than those on the surface. Inside this layer, which extends from Georges Bank to Sable Island, water temperature can be above 8 °C. In light of the Atlantic mackerel’s (Scomber scombrus L.) thermal preference, this layer of water could represent an appropriate wintering area for this species. Mackerel catches made chiefly in this layer of water using midwater trawls by foreign vessels between 1990 and 1992 appear to confirm this hypothesis

GRÉGOIRE, F., C. LÉVESQUE, J.L. BEAULIEU, J. HUDON, 2006. Assessment of the Atlantic mackerel (Scomber scombrus L.) spawning stock biomass from the 2003, 2004, and 2005 egg surveys. DFO, Canadian Science Advisory Secretariat, Research Document, 2006/100, 48 p .

Click to see all the text

The data that was collected during egg surveys conducted in the southern Gulf of St. Lawrence indicate a significant drop in mackerel spawning biomass since 2003. This drop could be caused above all by particular environmental conditions. In fact, for the surveys conducted since 2003, the most significant egg concentrations were found in only one small region located in the south-western part of the sampled area. This particular egg distribution pattern has never before been observed and would be associated with the presence of cold waters that covered an important portion of the Gulf of St. Lawrence during these surveys. These cold waters could also be the cause for recent changes in migration routes and the unusual and very abundant occurrence of mackerel on the east coast of Newfoundland. We recommend that the egg survey be extended outside the Gulf of St. Lawrence in order to improve the assessment of mackerel abundance. In addition, because of the recent increase in American and Canadian landings, we recommend an international egg survey between the Unites-States and Canada. This survey could be conducted periodically and cover the species’ two principal spawning grounds in the northwest Atlantic.

HEIGHTON, R., F. GRÉGOIRE, 2006. A hook selectivity study for Atlantic mackerel (Scomber scombrus L.) caught in St. Georges Bay, Nova Scotia, in October 2005. Can. Ind. Rep. Fish. Aquat. Sci., 278, 57 p .

Click to see all the text

Following a proposal by the Northumberland Fishermen’s Association, a study was conducted in the fall of 2005 on the selectivity of hooks used in the Atlantic mackerel commercial fishery. The study lasted six days in St. Georges Bay, Nova Scotia. Two lines equipped with around forty hooks each were used for each fishing trip. One of the lines, called the "control" line and used during every trip, had number 10 sized hooks; the other lines had 2/0 or 4/0 sized hooks. The length distribution frequency of Atlantic mackerel caught by these hooks is characterized by two main modes: the main one around 300 mm and the other around 350 mm. The latter mode is associated with catches made using the 4/0 hooks. These results encourage to continue this study in order to determine a more selective hook shape and size that might help catch larger individuals while reducing the number of smaller Atlantic mackerel caught, which will reduce the mortality of small fish by discards at sea.

GRÉGOIRE, F., 2006. Mise à jour des données de la pêche au maquereau bleu (Scomber scombrus L.) couverte par le programme des observateurs de la Nouvelle-Écosse (1977-2005) ; Data update on the Atlantic mackerel (Scomber scombrus L.) fishery covered by the Nova Scotia Observer Program (1977-2005). MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2006/096, 44 p .

Click to see all the text

Fishing activities by foreign and Canadian vessels on the Scotian Shelf and Georges Bank have been covered since 1977 by the Nova Scotia Observers Program. The mackerel catch data collected under this program has been updated and analyzed based on country of origin, the area fished, month, depth and fishing gear used. The length and orientation of sets have also been examined, as well as the length frequency distribution for the sampled catches. Results show that the most significant mackerel catches were made in the early 1990s, on the edge of the continental shelf, between April and June. Mackerel have also been caught in other months, suggesting their presence throughout the year on the Scotian Shelf. The same dominant year-classes recorded in the Canadian commercial fishery have been observed in the catches made by foreign vessels. At times, smaller size mackerel were caught by some of these vessels. It was not possible to define any clear mackerel migration and distribution pattern on the Scotian Shelf based on the data provided by the observers because the fishing activities of foreign vessels were concentrated only on the edge of the continental shelf and that several other species were the target of this fishery

GRÉGOIRE, F., 2006. Assessment of the atlantic mackerel for the Northwest Atlantic (Subareas 3 and 4) in 2005. DFO, Canadian Science Advisory Secretariat, Science Advisory Report, 2006/033, 17 p .

Click to see all the text

GRÉGOIRE, F., C. LAFLEUR, 2006. Distribution et abondance des œufs et des larves de maquereau bleu (Scomber scombrus L.) des relevés d'ichtyoplancton réalisés dans le sud du golfe du Saint-Laurent entre 1965 et 1975 ; Distribution and abundance of the Atlantic mackerel (Scomber scombrus L.) eggs and larvae from the ichthyoplankton surveys conducted in the southern Gulf of St. Lawrence between 1965 to 1975. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2006/098, 114 p .

Click to see all the text

In the Gulf of St. Lawrence, the first large scale ichthyoplankton surveys were conducted by Kohler between 1965 and 1975. During this period, a total of 35 surveys were made from May to October at a rate of 2–5 surveys per year. Atlantic mackerel eggs and larvae were collected on most of these surveys. A large number of sampling gears were used but standard nets deployed on the surface and at 15 m yielded eggs at a significant number of stations. Eggs were not only collected as early as May, but also quite late in the season, i.e. in September and October. In May, most of the eggs were found around the Magdalen Islands and in June, between New Brunswick and the Magdalen Islands. The most significant abundances of eggs were recorded in June

GRÉGOIRE, F., C. LÉVESQUE, J.L. BEAULIEU, J. HUDON, 2006. Évaluation de la biomasse reproductrice du maquereau bleu (Scomber scombrus L.) selon les relevés des œufs realisés en 2003, 2004 et 2005 ; Assessment of the Atlantic mackerel (Scomber scombrus L.) spawning stock biomass from the 2003, 2004, and 2005 egg surveys. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2006/100, 48 p .

Click to see all the text

The data that was collected during egg surveys conducted in the southern Gulf of St. Lawrence indicate a significant drop in mackerel spawning biomass since 2003. This drop could be caused above all by particular environmental conditions. In fact, for the surveys conducted since 2003, the most significant egg concentrations were found in only one small region located in the south-western part of the sampled area. This particular egg distribution pattern has never before been observed and would be associated with the presence of cold waters that covered an important portion of the Gulf of St. Lawrence during these surveys. These cold waters could also be the cause for recent changes in migration routes and the unusual and very abundant occurrence of mackerel on the east coast of Newfoundland. We recommend that the egg survey be extended outside the Gulf of St. Lawrence in order to improve the assessment of mackerel abundance. In addition, because of the recent increase in American and Canadian landings, we recommend an international egg survey between the Unites-States and Canada. This survey could be conducted periodically and cover the species’ two principal spawning grounds in the northwest Atlantic

GRÉGOIRE, F., S. FAUCHER, 2006. Distribution et abondance des œufs de maquereau bleu (Scomber scombrus L.) pour les relevés d'ichtyoplancton réalisés dans le sud du golfe du Saint-Laurent entre 1976 et 1979 ; Distribution and abundance of the Atlantic mackerel (Scomber scombrus L.) eggs for the ichthyoplankton surveys conducted in the southern Gulf of St. Lawrence between 1976 to 1979. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2006/099, 28 p .

Click to see all the text

Ichthyoplankton surveys were conducted in the southern Gulf of St. Lawrence between 1976 and 1979. Mackerel eggs were collected during these surveys using standard nets towed on the surface and Bongo nets towed obliquely in a saw-tooth pattern. The mean abundance of eggs measured during these surveys using standard nets varied between 6,194 and 8,440 eggs/100 m³. These abundances are far superior to those measured during the surveys conducted in the southern Gulf between 1965 and 1975. The mean abundance of eggs measured in 1979 using Bongo nets was 433 eggs/m². A mean abundance of 194 eggs/m² was measured for eggs of development stages 1 and 5. Because fecundity data is available for 1979, this mean abundance could be converted to spawning biomass and compared with biomasses obtained during the surveys realized since 1983 in the southern Gulf of St. Lawrence

GRÉGOIRE, F., 2006. Assessment of the west coast of Newfoundland (division 4R) herring stocks in 2005. DFO, Canadian Science Advisory Secretariat, Science Advisory Report, 2006/021, 12 p .

Click to see all the text

GRÉGOIRE, F., 2006. Assessment of the Quebec North Shore (division 4S) herring stocks in 2005. DFO, Canadian Science Advisory Secretariat, Science Advisory Report, 2006/020, 14 p .

Click to see all the text

GRÉGOIRE, F., 2006. Assessment of the Estuary and Gulf of St. Lawrence (divisions 4RST) capelin stock in 2005. DFO, Canadian Science Advisory Secretariat, Science Advisory Report, 2006/022, 12 p .

Click to see all the text

GRÉGOIRE, F., 2005. Capelan de l'estuaire et du golfe du Saint-Laurent (4RST) en 2004. MPO, Secrétariat canadien de consultation scientifique, Avis scientifique, 2005/002, 9 p .

Click to see all the text

GREGOIRE, F., W. BARRY, J. BARRY, L. LEFEBVRE, C. LEVESQUE, J. HUDON, 2005. West coast of Newfoundland capelin (Mallotus villosus M.) and Atlantic herring (Clupea harengus harengus L.) larval survey, part 1: Description of the data collected in partnership with the industry (Barry Group) in July 2004. Can. Data Rep. Fish. Aquat. Sci., 1168, 38 p .

Click to see all the text

In partnership with the Barry Group in Corner Brook, a larval survey was conducted from July 15 to 17, 2004, between Bonne Bay and Port au Port Bay on the west coast of Newfoundland. Fish eggs and larvae were found at all the sampled stations. The two most abundant groups of eggs that were identified were CYT (cunner [Tautogolabrus adspersus] and yellowtail flounder [Limanda ferruginea]), and CHW (cod [Gadus morhua], haddock [Melanogrammus aeglefinus], and witch flounder [Glyptocephalus cynoglossus]). Mackerel eggs (Scomber scombrus L.) were also found at most of the stations. Of the twenty species of larvae identified, the most notable were those of capelin (Mallotus villosus M.), herring (Clupea harengus harengus L.), cod, righteye flounder (Pleuronectidae spp.), and cunner. Depth-based profiles of water temperature and salinity were made for each station. All the biological and oceanographic data collected during the survey were compiled and are presented in the tables, figures, and appendices found in this document. These data will be analyzed and published in a second report

GRÉGOIRE, F., 2005. Maquereau bleu du nord-ouest de l'Atlantique en 2004. MPO, Secrétariat canadien de consultation scientifique, Avis scientifique, 2005/014, 10 p .

Click to see all the text

GRÉGOIRE, F., 2005. Hareng de la côte ouest de Terre-Neuve (Division 4R) en 2004. MPO, Secrétariat canadien de consultation scientifique, Avis scientifique, 2005/016, 10 p .

Click to see all the text

FRÉCHET, A., F. GRÉGOIRE, 2005. Calcul de la mortalité naturelle de la morue (Gadus morhua) du nord du golfe du Saint-Laurent pour la période de 1990 à 2004 ; Calculation of Northern Gulf of St. Lawrence cod (Gadus morhua) natural mortality for the 1990 to 2004 period. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2005/019, 23 p .

Click to see all the text

[Abstract only available in French]
L’analyse séquentielle de populations a été utilisée pour calculer la mortalité naturelle de la morue (Gadus morhua) du nord du golfe du Saint-Laurent (divisions 3Pn,4RS de l’OPANO). Les calculs ont été réalisés à l’aide du logiciel ADAPT pour des périodes variant de 4 à 9 ans. Les diagnostics et les résultats de ces analyses sont similaires d’un modèle à l’autre et par rapport à la formulation de base utilisée dans l’évaluation d’abondance. Les résultats suggèrent aussi une diminution graduelle de la mortalité naturelle au cours des années 1990 et 2000

FRÉCHET, A., F. GRÉGOIRE, 2005. Calculation of Northern Gulf of St. Lawrence cod (Gadus morhua) natural mortality for the 1990 to 2004 period. DFO, Canadian Science Advisory Secretariat, Research Document, 2005/019, 23 p .

Click to see all the text

Sequential population analysis was used to calculate natural mortality of the northern Gulf of St. Lawrence cod (Gadus morhua) in NAFO Divisions 3Pn,4RS. Calculations were made using the ADAPT software for periods ranging between 4 and 9 years. The diagnosis and results of these analyses are similar from one model to the other and according to the basic formulation used for the abundance assessment. Results also suggest a gradual drop in natural mortality during the 1990s and 2000s

GRÉGOIRE, F., C. SAVENKOFF, 2005. Pêche, biologie, régime alimentaire et prédation du maquereau bleu (Scomber scombrus L.) dans les sous-régions 3 et 4 de l’OPANO en 2004. MPO, Secrétariat canadien de consultation scientifique, Document de recherche, 2005/056, 63 p .

Click to see all the text

In 2004, landings of Atlantic mackerel (Scomber scombrus L.) in the northwest Atlantic totalled 87,980 t, up to 8,489 t from 2003. In eastern Canada, 35,023 t were landed, including 32,966 t in Newfoundland only. The actual landings of 2004 should be higher since landings data from Prince Edward Island, New Brunswick, and Nova Scotia have not yet been accounted for. On the west coast of Newfoundland, the most important catches were realized in unit areas 4Rb (2,478 t), 4Rc (11,426 t), and 4Rd (7,492 t) in comparison with 3Kd (1,029 t) and 3Kh (10,123 t) for the east coast. Mackerel catches of this importance is unusual for the east coast of Newfoundland. The other important unit areas were 4Tf (966 t) and 4Xm (2,288 t) located respectively in the Magdalen Islands and close to Halifax, Nova Scotia. Since 2000, the most striking feature of commercial mackerel catches has been the presence of a high abundance and very large proportion of fish from the 1999 year-class. Over the past five years, this year-class has accounted for between 56 % and 77 % of the total number of fish caught, which hasn’t been seen since the late 1960s. In 2004, one- and two-year age groups were also predominant in fall catches made in the Southern Gulf of St. Lawrence (using lines) and on the East coast of Newfoundland (using purse seines). The presence of small mackerel in the latter area is unusual. Data collected in the mid-1980s showed that mackerel in the Northern Gulf of St. Lawrence fed mainly on small (< 5 mm) and large (= 5 mm) zooplankton. As shown by the results of a model of the Northern Gulf of St. Lawrence marine ecosystem, the main causes of mortality for mackerel in the mid-1980s were cetaceans, large cod (Gadus morhua), and large demersals. The proportion of mackerel making up the cetacean and large cod diets during this period was 18.7 % and 1.5 % respectively. The same model showed that fishery related mortalities gradually increased from 2 % in the early 1980s to 15 % in the mid-1990s, and finally to 27 % in the early 2000s.

GRÉGOIRE, F., C. SAVENKOFF, D. CHABOT, 2005. Capelin (Mallotus villosus) of the Estuary and Gulf of St. Lawrence (NAFO Divisions 4RST) in 2004. DFO, Canadian Science Advisory Secretariat, Research Document, 2005/058, 55 p .

Click to see all the text

In 2004, capelin landings fished in the Estuary and the Gulf of St. Lawrence added up to 6,089 t. These landings represent a rise of 1,057 t compared with the 2003 level. With this increase, the 2004 landings are now just over the annual average landings of 5,487 t calculated for the 1990-2003 period. Purse seiners operating on the west coast of Newfoundland, and in unit area 4Rc in particular made for 76 % of landings realized in 2004. Between the end of the 1980s and the beginning of the 1990s, fishing seasons in this area were generally characterized by late fishery opening dates (and spawning activities). However, a relative stability in fishing dates has been observed since 2001. The average length of capelin caught in Division 4R showed a downward trend between 1986 and 1999, but a rise occurred thereafter. Nevertheless, the lengths measured in 2004 remain lower to those recorded in the 1980s. The dispersion index of capelin in the Estuary and Gulf of St. Lawrence has been characterized by rises in its long-term tendencies between 1990 and 2004. However, in 2004, a reduction of the index was measured for the West coast of Newfoundland and the southern Gulf. Small and large zooplanktons remain capelin’s main food source. In the mid-1980s, the main causes of capelin mortality stem from predation of large cod (Gadus morhua) and redfish (Sebastes spp.). Cetaceans, harp seals (Phoca groenlandica) and Greenland halibut (Reinhardtius hippoglossoides) replaced these two species during the 1990s and 2000s. In the mid-1980s, annual capelin consumption by its main predators totalled approximately one million tonnes. In the early 2000s, despite the strong decrease in abundance of its predators (cod and redfish), nearly 400,000 t of capelin per year was still being consumed, making this species the most important prey in the northern Gulf of St. Lawrence ecosystem.

GRÉGOIRE, F., 2005. West coast of Newfoundland Atlantic herring (Division 4R) in 2004. DFO, Canadian Science Advisory Secretariat, Science Advisory Report, 2005/016, 9 p .

Click to see all the text

GRÉGOIRE, F., 2005. Atlantic mackerel of the Northwest Atlantic in 2004. DFO, Canadian Science Advisory Secretariat, Science Advisory Report, 2005/014, 9 p .

Click to see all the text

GRÉGOIRE, F., 2005. Capelin of the Estuary and Gulf of St. Lawrence (4RST) in 2004. DFO, Canadian Science Advisory Secretariat, Science Advisory Report, 2005/002, 8 p .

Click to see all the text

GRÉGOIRE, F., 2005. Mise à jour (septembre 2005) des débarquements de maquereau (Scomber scombrus L.) des sous-régions 3 et 4 de l'OPANO en 2004 ; Update (September 2005) of the Atlantic mackerel (Scomber scombrus L.) landings in NAFO Subareas 3 and 4 in 2004. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2005/057, 17 p .

Click to see all the text

[Abstract only available in French]
L’analyse et la présentation des données de la pêche commerciale au maquereau (Scomber scombrus L.) pour la saison 2004 ont été réalisées sans les débarquements provenant de l’Île-du-Prince-Édouard, du Nouveau-Brunswick et de la Nouvelle-Écosse. Compte tenu que les captures de maquereau dans ces provinces ont toujours été importantes, il a été convenu lors du Processus de consultation scientifique régional de mettre à jour les débarquements de la saison 2004 dès que toutes les données seraient disponibles. Ces dernières ont finalement été rendues disponibles en mai 2005. Le présent document décrit les principaux résultats de cette mise à jour.

GRÉGOIRE, F., C. SAVENKOFF, D. CHABOT, 2005. Capelan (Mallotus villosus) de l’estuaire et du golfe du Saint-Laurent (divisions 4RST de l’OPANO) en 2004. MPO, Secrétariat canadien de consultation scientifique, Document de recherche, 2005/058, 55 p .

Click to see all the text

In 2004, capelin landings fished in the Estuary and the Gulf of St. Lawrence added up to 6,089 t. These landings represent a rise of 1,057 t compared with the 2003 level. With this increase, the 2004 landings are now just over the annual average landings of 5,487 t calculated for the 1990-2003 period. Purse seiners operating on the west coast of Newfoundland, and in unit area 4Rc in particular made for 76 % of landings realized in 2004. Between the end of the 1980s and the beginning of the 1990s, fishing seasons in this area were generally characterized by late fishery opening dates (and spawning activities). However, a relative stability in fishing dates has been observed since 2001. The average length of capelin caught in Division 4R showed a downward trend between 1986 and 1999, but a rise occurred thereafter. Nevertheless, the lengths measured in 2004 remain lower to those recorded in the 1980s. The dispersion index of capelin in the Estuary and Gulf of St. Lawrence has been characterized by rises in its long-term tendencies between 1990 and 2004. However, in 2004, a reduction of the index was measured for the West coast of Newfoundland and the southern Gulf. Small and large zooplanktons remain capelin’s main food source. In the mid-1980s, the main causes of capelin mortality stem from predation of large cod (Gadus morhua) and redfish (Sebastes spp.). Cetaceans, harp seals (Phoca groenlandica) and Greenland halibut (Reinhardtius hippoglossoides) replaced these two species during the 1990s and 2000s. In the mid-1980s, annual capelin consumption by its main predators totalled approximately one million tonnes. In the early 2000s, despite the strong decrease in abundance of its predators (cod and redfish), nearly 400,000 t of capelin per year was still being consumed, making this species the most important prey in the northern Gulf of St. Lawrence ecosystem.

SAVENKOFF, C., F. GREGOIRE, M. CASTONGUAY, D.P. SWAIN, D. CHABOT, J.M. HANSON, 2005. Main prey and predators of Atlantic mackerel (Scomber scombrus L.) in the northern and southern Gulf of St. Lawrence during the mid-1980s, mid-1990s, and early 2000s. Can. Tech. Rep. Fish. Aquat. Sci., 2619, 34 p .

Click to see all the text

We used results of mass-balance models to describe the changes in the structure and functioning of the northern and southern Gulf of St. Lawrence ecosystems related to the Atlantic mackerel (Scomber scombrus L.) stock for the mid-1980s, the mid-1990s, and the early 2000s. The net decrease in biomass of demersal species and the ensuing drop in predation from the mid-1980s to the mid-1990s led to an ecosystem structure dominated by small-bodied pelagic species and marine mammals in the northern and southern Gulf. Predation was the main cause of mackerel mortality in each ecosystem for all time periods. However, demersal predators such as large cod and large demersals were progressively replaced by cetacea and seals as the main mackerel predators from the mid-1980s to mid-1990s (and early 2000s in the northern Gulf). Over the same time period, fishing mortality increased and became the second highest mortality cause in the northern Gulf for the early 2000s and the main mortality cause in the southern Gulf for the mid-1990s. Fishing mortality may have been underestimated due to non-negligible underreporting (discards at sea, recreational catches, and catches by bait fishermen)

GRÉGOIRE, F., L. LEFEBVRE, J. GUÉRIN, J. HUDON, J. LAVERS, 2004. Le hareng (Clupea harengus harengus L.) de la côte ouest de Terre-Neuve (Division 4R de l'OPANO) en 2003 ; Atlantic herring (Clupea harengus harengus L.) on the West coast of Newfoundland (NAFO Division 4R) in 2003. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2004/078, 74 p .

Click to see all the text

The 2003 herring landings (Clupea harengus harengus L.) on the West coast of Newfoundland amounted to 14,681 t, representing 73 % of the Total Allowable Catch (TAC). The most significant landings were recorded in unit area 4Rd, with 10,546 t. The large seiners alone unloaded 11,090 t of herring on a quota of 11,000 t, compared to 2,307 t or 52 % of their quota for the small seiners, and 1,284 t or 28 % of their quota for fishermen using gillnet. The catch-at-age of spring spawners was dominated by the year-class of 1996, with 26.5 % of all the catches, and that of the fall spawners, by the year-class of 2000, with 34.1 % of the catches. The condition (index of Fulton) of the spring and fall spawners declined sharply in 2003, following major gains between 1998 and 2002. Almost all the 4 year old herrings and more are mature and, compared to the 1960s and 1970s, sexual maturity is now reached earlier, in particular for the spring spawners. Herring is generally caught in the whole sampling area covered by the annual scientific surveys conducted to assess groundfish and shrimp (Pandalus borealis) abundance in the northern Gulf of St. Lawrence. During these surveys, the most significant herring catches are realized in the area of Anticosti, on the lower North Shore of Quebec, and on the West coast of Newfoundland, at the head of the Esquiman Channel. Two dispersion indices calculated by indicator kriging show an upward trend between 1990 and 2001, followed by an important decline in 2003. For the West coast of Newfoundland, these two indices were relatively stable between 1993 and 1997. They increased rapidly after that and declined again in 2003.

SAVENKOFF, C., F. GRÉGOIRE, D. CHABOT, 2004. Main prey and predators of capelin (Mallotus villosus) in the northern and southern Gulf of St. Lawrence during the mid-1980s and mid-1990s. Can. Tech. Rep. Fish. Aquat. Sci., 2551, 30 p .

Click to see all the text

Based on the results of mass-balance models, we present here the changes in the structure and functioning of the northern and southern Gulf of St. Lawrence ecosystems related to the capelin stock (Mallotus villosus) from the pre- to post-collapse period of the groundfish stocks, which were the main predators of capelin. The net decrease in biomass of these demersal species and the ensuing drop in predation from the mid-1980s to the mid-1990s led to an ecosystem structure dominated by small-bodied pelagic species and marine mammals in the northern and southern Gulf. Capelin is an important prey for many fish species (cod [Gadus morhua] and redfish [Sebastes spp.] in the northern Gulf; cod and mackerel [Scomber scombrus] in the southern Gulf) and for marine mammals (cetacea and seals). Capelin plays a key role in the food web by transferring energy from primary and secondary producers (on which it feeds) to higher trophic levels of the demersal and pelagic domains of the Gulf of St. Lawrence. Capelin was the main fish predator of small and large zooplankton in the northern Gulf for each time period and was also the main prey consumed by fish and marine mammals.

GREGOIRE, F., R. MORNEAU, G. CARON, M. BEAUDOIN, C. LEVESQUE, C. ROSE, A. FELIX, J. HUDON, 2004. Fécondité du capelan (Mallotus villosus) dans l’estuaire et le golfe du Saint-Laurent en 2003. Rapp. tech. can. sci. halieut. aquat., 2560, 22 p .

Click to see all the text

A capelin fecundity study was carried out in the Estuary and Gulf of St. Lawrence in 2003. Ovaries were collected at three of the most important fishing locations between 10 May and 1 July. The fecundity, obtained using the gravimetric method, was evaluated at 18,326 eggs for the ovaries sampled in the Lower St. Lawrence compared to 16,129 eggs and 19,559 eggs for those coming from Sept-Îles and Newfoundland. Linear regressions were used to describe the relationships between fecundity, weight, and fresh length. Slopes of these regressions were not significantly different from one site to another. Histological examination of the ovaries revealed that the development of the vitellogenic or mature oocytes is synchronous. The mean diameter of the vitellogenic oocytes from Lower St. Lawrence capelin was 0.610 mm compared to 0.613 mm and 0.619 mm from Sept-Îles and Newfoundland capelin. A large difference was observed between the frequency distributions of vitellogenic and previtellogenic oocyte diameters. This means that capelin spawning is determinate. We found that capelin fecundity can be calculated rapidly from a relationship between the mean number of oocytes per gram of ovary and the mean oocyte diameter. Fecundities obtained with this relationship are similar to those calculated using the gravimetric method.

GRÉGOIRE, F., C. LÉVESQUE, J. GUÉRIN, J. HUDON, J. LAVERS, 2004. Pêche et biologie du maquereau bleu (Scomber scombrus L.) dans les sous-régions 3 et 4 de l'OPANO en 2003 ; Atlantic mackerel (Scomber scombrus L.) fishery and biology in NAFO Subareas 3 and 4 in 2003. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2004/079, 57 p .

Click to see all the text

In 2003, landings of Atlantic mackerel (Scomber scombrus L.) in the northwest Atlantic totalled 65,512 t, up to 3,372 t from 2002. In eastern Canada, 34,413 t were landed, a submit since 1960, including 26,295 t in Newfoundland only. The most important catches of this province were realized in unit areas 4Rb, 4Rc, and 4Rd. The other important unit areas were 4Tf and 4Xm, located respectively in the Magdalen Islands and close to Halifax, Nova Scotia. The catch at age associated to the 2003 Canadian landings was characterized by a very large number of fish 4 years old, from the 1999 year-class. At ages 1 to 4 years old, the fish in this year-class accounted for 63%, 68 %, 77 %, and 75 % of the total catch (in numbers) made between 2000 and 2003. Such values have never been observed in the year-classes that have dominated the fishery since the late 1960s.

GRÉGOIRE, F., 2004. Capelan de l'estuaire et du golfe du Saint-Laurent (4RST) en 2003. Rapport sur l'état des stocks, 2004/001, 14 p .

Click to see all the text

GRÉGOIRE, F., 2004. Capelin of the Estuary and Gulf of St. Lawrence (4RST) in 2003. Science, Stock Status Report, 2004/001, 14 p .

Click to see all the text

GRÉGOIRE, F., 2004. Hareng de la côte ouest de Terre-Neuve (Division 4R) en 2003. Rapport sur l'état des stocks, 2004/017, 10 p .

Click to see all the text

GRÉGOIRE, F., 2004. West Coast of Newfoundland Atlantic Herring (Division 4R) in 2003. Science, Stock Status Report, 2004/017, 10 p .

Click to see all the text

GRÉGOIRE, F., 2004. Maquereau bleu du nord-ouest de l’Atlantique en 2003. Rapport sur l'état des stocks, 2004/018, 13 p .

Click to see all the text

GRÉGOIRE, F., L. LEFEBVRE, J. LAVERS, 2004. Évaluation analytique et analyses de risque pour les stocks de hareng (Clupea harengus harengus L.) de la côte ouest de Terre-Neuve (Division 4R de l'OPANO) en 2002 ; Analytical assessment and risk analyses for the herring (Clupea harengus harengus L.) stocks on the west coast of Newfoundland (NAFO Division 4R) in 2002. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2004/060, 92 p .

Click to see all the text

Sequential Population Analyses (SPA) were realized in 2003 on the spring-spawning and fall-spawning stocks of herring (Clupea harengus harengus L.) of the west coast of Newfoundland (NAFO Division 4R). The results of these analyses revealed that the spawning biomass of the spring stock appears to have risen from 35,011 t in 1997 to 67,851 t in 2002, and to 58,921 t in 2003. This last value is greater than the minimum acceptable limit B_LIM of 37,834 t, but close to the buffer limit B_BUF of 57,468 t. Fishing mortality among the oldest individuals (age 8 and older) would have exceeded the F_0.1 threshold on a few occasions in the late 1960s and the early 1980s and almost continuously throughout the 1990s. For this same stock, the probabilities of exceeding F_0.1 in 2003 would be less than 50 % for catches of less than 11,000 t. For the fall-spawning herring stock, the spawning biomass appears to have fallen from 71,412 t in 1994 to 53,373 t in 2002 and to 48,481 t in 2003. This last value is slightly greater than the B_LIMvalue of 47,953 t, but lower than the B_BUF limit of 61,074 t. For this stock, the probabilities of exceeding F_0.1 in 2003 would be less than 50 % for catches of less than 11,600 t. Results of the SPA reveal also important impreciseness in the calculation of some parameters and the presence of a retrospective pattern denoting a tendency to underestimate the real abundance of these two stocks. Consequently, the results of the SPA must be used with caution, and greater uncertainty must be ascribed to the projections derived from the risk analyses. Therefore, we are recommending a gradual increase in the TAC which should not exceed 20,000 t in 2003.

GRÉGOIRE, F., C. SAVENKOFF, H. BENOÎT, D. CHABOT, C. LÉVESQUE, J. HUDON, J. LAVERS, 2004. Pêche, biologie et distribution du capelan (Mallotus villosus) dans les divisions 4RST de l'OPANO en 2003 ; Capelin (Mallotus villosus) fishery, biology and distribution in NAFO Divisions 4RST in 2003. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2004/136, 79 p .

Click to see all the text

In 2003, capelin landings fished in the Estuary and the Gulf of St. Lawrence added up to 4,640 t. These landings represent a rise of 1,248 t compared with the 2002 level. However, despite this increase, the 2003 landings are still lower than the annual average landings of 5,522 t calculated for the 1990-2002 period. According to the industry, the recent drop in capelin landings would be caused by the loss of some significant markets and not a decrease in the abundance. The majority of landings realized in 2003 were made by purse seiners operating on the west coast of Newfoundland, and in unit area 4Rc in particular. Between the end of the 1980s and the beginning of the 1990s, fishing seasons in this area were generally characterized by late fishery opening dates (and spawning activities). The average length of capelin caught in Division 4R showed a downward trend between 1986 and 1999, but a rise occurred thereafter. Nevertheless, the lengths measured in 2003 still remain lower to those recorded in the 1980s. Indices measuring the dispersion and probabilities of finding capelin are now calculated from the groundfish and shrimp (Pandalus borealis) abundance research surveys. Between 1990 and 2003, these indices have been characterized by rises in their long-term tendencies. From 1997 to 2002, areas with high probabilities to find capelin in the northern Gulf of St. Lawrence expanded gradually towards the east. However in 2003, the west coast of Newfoundland was rather characterized by a reduction of such areas. For the southern Gulf, a very significant expansion of the species distribution characterized this area since the middle of the 1990s. This expansion seems to be linked with a reduction of the Magdalen Shallows surface area covered by water colder than 1 °C. Stomach contents sampled in the Gulf of St. Lawrence (Divisions 4R and 4S) since 1993 revealed that the capelin is a significant food resource for cod (Gadus morhua). A strong link would exist between the length of cod and the importance of capelin in its diet. Indeed, cods from 20 to 70 cm would be the most important predator for capelin.

GRÉGOIRE, F., L. LEFEBVRE, J. LAVERS, 2004. Évaluation analytique et analyses de risque pour le stock des harengs (Clupea harengus harengus L.) de printemps de la côte ouest de Terre-Neuve (Division 4R de l'OPANO) en 2003 ; Analytical assessment and risk analyses for the spring spawning herring (Clupea harengus harengus L.) stock of the west coast of Newfoundland (NAFO Division 4R) in 2003. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2004/090, 70 p .

Click to see all the text

The results of a Sequential Population Analysis (SPA) reveal that the spawning biomass of the spring spawning stock of Atlantic herring (Clupea harengus harengus L.) in NAFO Division 4R appears to have risen from a record low of 32,559 t in 1997 to 57,727 t in 2003 and 52,582 t in 2004. The spawning stock biomass calculated for 2004 exceeds the minimum acceptable limit B_LIM of 37,831 t but is below the buffer limit B_BUF of 57,453 t. The SPA reveals that the herring became significantly more abundant in the late 1960s and the mid-1980s. The SPA also reveals that fishing mortality among the oldest individuals (age 8 and older) exceeded the F_0,1 threshold on a few occasions in the late 1960s and the early 1980s and almost continuously throughout the 1990s. For an exploitation rate of 24 % (F_0,1), the expected catches in 2004 would be close to 10,000 t. However, a decline of 8 % of the spawning stock biomass would be observed at this same catch level. For this stock, the probabilities of exceeding F_0,1 in 2004 would be less than 50 % for catches of less than 10,000 t.

BOURDAGES, H., D. ARCHAMBAULT, B. MORIN, A. FRÉCHET, L. SAVARD, F. GRÉGOIRE, R. DUFOUR, 2004. Résultats préliminaires du relevé multidisciplinaire de poissons de fond et de crevette d'août 2004 dans le nord du golfe du Saint-Laurent ; Preliminary results from the groundfish and shrimp multidisciplinary survey from August 2004 in the northern Gulf of St. Lawrence. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2004/112, 40 p .

Click to see all the text

As a result of the delays in putting the CCGS Alfred Needler into operation, the August 2004 multidisciplinary groundfish and shrimp survey in the northern Gulf of St. Lawrence was conducted aboard the CCGS Teleost, which itself suffered major damage, delaying the start of the mission. The survey was conducted between August 15 and September 2, corresponding to a period that was just over half of the time initially planned. A total of 130 tows were made throughout the area, 95 % of which were successful. Summary findings for catch rates, catch rate distributions and size frequency distributions are presented for 14 species, including the 4 species targeted by the survey (cod, Greenland halibut, redfish and Northern shrimp). However, the 2004 findings are preliminary and must be considered as such until laboratory analyses and data validation have been completed. With the exception of data on the spatial distribution of catches, data obtained during this survey cannot be compared with data obtained during previous missions aboard the CCGS Alfred Needler until conversion indices for each species will be calculated using data obtained during comparative missions. Data gathered in 2004 on the catch distribution of the various species indicate a pattern similar to those observed in previous years aboard the CCGS Alfred Needler.

GRÉGOIRE, F., C. D'ENTREMONT, C. LÉVESQUE, C. McGILLIVRAY, L. LEFEBVRE, D. SMITH, J. GEHUE, 2004. Atlantic mackerel (Scomber scombrus L.) maturity study : (1) Biological data collected in partnership with the industry at the Martine Marie Fishery Ltd. Plant (Barry Group), Middle West Pubnico, Nova Scotia, between 2001 and 2003. Can. Data Rep. Fish. Aquat. Sci., 1152, 84 p .

Click to see all the text

In partnership with the industry, a maturity study on Atlantic mackerel (Scomber scombrus L.) was conducted at the Martine Marie Fishery Ltd. plant, Middle West Pubnico, Nova Scotia, between 2001 and 2003 inclusively. During this study, a total of 13,840 fish were measured; of this number, 2,284 specimens were frozen at the plant before being sent to the DFO laboratory in Mont-Joli. At the plant, ovaries were also collected and preserved in a formaldehyde solution for histological examination. Data from laboratory analyses were validated and used to calculate the condition (Fulton) and gonado-somatic indices. All data were compiled and presented in the tables, figures, and appendices of this document. These data will be analysed and published in future reports

GRÉGOIRE, F., 2004. Atlantic Mackerel of the Northwest Atlantic in 2003. Science, Stock Status Report, 2004/018, 12 p .

Click to see all the text

GREGOIRE, F., 2003. West coast of Newfoundland Atlantic herring (Division 4R) in 2002. Science, Stock Status Report, 2003/008, 11 p .

Click to see all the text

GREGOIRE, F., 2003. Maquereau bleu du nord-ouest de l'Atlantique en 2002. Rapport sur l'état des stocks, 2003/010, 11 p .

Click to see all the text

GRÉGOIRE, F., L. LEFEBVRE, 2003. Biological characteristics of Atlantic herring (Clupea harengus harengus L.) from Newfoundland's west coast for the 1965-2001 period. Can. Ind. Rep. Fish. Aquat. Sci., 270, 38 p. .

Click to see all the text

Commercial herring landings on Newfoundland's west coast have been sampled regularly since the mid-1960s. An analysis of the collected samples indicates that the two spawning stocks have identical growth rates (length and weith). However, variations have been noted over the years. For example, although the 1980s were distinguished by more rapid herring growth, the dominant yearat a younger age and spawning has occurred at a later date.

GRÉGOIRE, F., L. LEFEBVRE, 2003. Estimation of gillnet selectivity for Atlantic herring (Clupea harengus harengus L.) from the west coast of Newfounland, 1997-2001. Can. Ind. Rep. Fish. Aquat. Sci., 272, 22 p. .

Click to see all the text

Atlantic herring (Clupea harengus harengus L.) is commercially fished off the west coast of Newfoundland by a large number of fishers using gillnets. Gillnets are a very selective fishing gear, so fishers use different mesh sizes to maximize captures. We calculated gillnet selectivity for three different mesh sizes using catch data from index fishers for the 1997 to 2001 period. The results of this study demonstrate that the probability of capturing larger Atlantic herring increases with mesh size. For example, in 1999, the modal lengths of herring estimated by a normal selectivity model were 38 cm, 39.9 cm and 41.8 cm for mesh sizes of 63.50 mm, 66.80 mm, and 69.85 mm, respectively. These results also demonstrate that there were changes in the modal lengths and selectivity for a given mesh size over the study period. Finally, a yield per recruit analysis indicates that the best yields would be obtained using nets with the smallest mesh size.

FRECHET, A., J. GAUTHIER, P. SCHWAB, H. BOURDAGES, D. CHABOT, F. COLLIER, F. GRÉGOIRE, Y. LAMBERT, G. MOREAULT, L. PAGEAU, J. SPINGLE, 2003. L'état du stock de morue du Nord du golfe du Saint-Laurent (3Pn, 4RS) en 2002 ; The status of cod in the Northern Gulf of St. Lawrence (3Pn, 4RS) in 2002. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2003/065, 90 p .

Click to see all the text

The commercial landings for this stock have reached a maximum of 106,000 tons while the stock had reached its maximum mature biomass of 462,000 tons in 1983. Afterwards, the stock was reduced to a minimum mature biomass of 21,000 tons in 1994. The stock was under moratorium from 1994 to 1996 which allowed for a modest improvement of the mature biomass which was at 58,000 tons at the reopening of the commercial fishery in 1997. Since 1997, the commercial fishery has been conducted by fixed gears only (longlines, gill nets and hand lines). Despite the low fishing effort, the mature biomass remains stable at the same low level as when the fishery was reopened in 1997.

GREGOIRE, F., 2003. Hareng de la cote ouest de Terre-Neuve (Division 4R) en 2002. Rapport sur l'état des stocks, 2003/008, 11 p .

Click to see all the text

GREGOIRE, F., 2003. Capelan de l'estuaire et du golfe du Saint-Laurent (4RST) en 2002. Rapport sur l'état des stocks, 2003/009, 14 p .

Click to see all the text

GREGOIRE, F., 2003. Atlantic mackerel of the Northwest Atlantic in 2002. Science, Stock Status Report, 2003/010, 11 p .

Click to see all the text

OUELLET, P., F. GRÉGOIRE, M. HARVEY, E. HEAD, B. MORIN, G. ROBERT, L. SAVARD, S. SMITH, M. STARR, D. SWAIN, 2003. Exceptional environmental conditions in 1999 in eastern Canadian waters and the possible consequences for some fish and invertebrate stocks. AZMP Bull. PMZA, 3: 21-27 .

Click to see all the text

[Abstract only available in French]
Plusieurs indicateurs des conditions atmosphériques indiquent que des températures de l’air anormalement élevées en 1999 ont entraîné une réduction de la glace de mer en hiver et au printemps sur les plateaux continentaux de Terre-Neuve, du Labrador et de la Nouvelle-Écosse et une augmentation des températures de l’eau de surface sur l’ensemble de la zone Atlantique. Également, d’autres indices indiquent que le cycle de production biologique (la floraison du phytoplancton) a été initié plus tôt en 1999 dans la plupart des régions de la zone. Ces conditions océanographiques exceptionnelles auraient eu des conséquences positives sur la production (ex. recrutement, croissance) de nombreux stocks de poissons et d’invertébrés dans l’Est du Canada.

GREGOIRE, F., 2003. Capelin in the estuary and the Gulf of St. Lawrence (4RST) in 2002. Science, Stock Status Report, 2003/009, 12 p .

Click to see all the text

GRÉGOIRE, F., H. BOURDAGES, J. ROY, 2002. Production d'un indice de dispersion pour le capelan (Mallotus villosus L.) de l'estuaire et du nord du golfe du Saint-Laurent par le krigeage d'indicatrice. Rapp. tech. can. sci. halieut. aquat., 2418, 21 p .

Click to see all the text

An index measuring the dispersion of capelin (Mallotus villosus L.) in the Estuary and Gulf of St. Lawrence was produced with indicator kriging. This index was calculated using the capelin catch data (kg/set) from the CCGV Alfred Needler groundfish and shrip (Pandalus borealis) research surveys that took place between 1990 and 2000. Data were transformed into a binary indicator function of capelin presence and absence. The spatial structure of this function was defined with variograms and the corresponding kriged values were used to calculate the minimal probabilities of finding capelin in a specific position. The proposed dispersion index was defined as the total sampled surface associated with a minimal presence probability of 50 %. Since 1990, this index has shown an increasing trend as has that of the percentage of occurance index, which is the current dispersion measurement used to capelin. However, a better delimitation of the dispersion zone was obtained with the indicator kriging because the calculation of this zone was based on the spatial structure of the catches.

BOURDAGES, H., D. ARCHAMBAULT, B. MORIN, A. FRÉCHET, L. SAVARD, F. GRÉGOIRE, M. BÉRUBÉ, 2002. Résultats préliminaires du relevé multidisciplinaire de poissons de fond et de crevette d'août 2002 dans le nord du golfe du Saint-Laurent ;. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2002/090, 69 p .

Click to see all the text

In 2002, the groundfish and shrimp multidisciplinary survey in the northern Gulf took place between August 1st and September 1st. A total of 207 fishing tows were conducted over the entire area of which 190 were successful, which corresponds to 76 % of the initial objective of 250 tows. Summary results concerning biomass and abundance, length frequencies and distribution of catch rates are presented for 13 species, including the four that are targeted by the survey (cod, Greenland halibut, redfish and shrimp). Results from 2002 are compared with those from previous years in order to have an indication of the trends for the 13 years time series. However results from 2002 are preliminary and must be considered as such pending laboratory analysis and completion of the validation of data. According to these preliminary results, biomass indices for cod, redfish, witch flounder and American plaice are very low in the northern Gulf while those of shrimp and Greenland halibut have remained high. A general decline in catches is observed for the majority of species along the West Coast of Newfoundland. However, the coverage of this area in 2002 was restricted due to frequent gear damage.

GRÉGOIRE, F., 2002. Hareng de la côte ouest de Terre-Neuve (Division 4R). Rapport sur l'état des stocks, B4-01, 11 p .

Click to see all the text

GRÉGOIRE, F., 2002. West coast of Newfoundland Atlantic herring (Division 4R). Science, Stock Status Report, B4-01, 10 p .

Click to see all the text

GRÉGOIRE, F., 2002. Hareng de la Côte-Nord du Québec (Division 4S). Rapport sur l'état des stocks, B4-02, 8 p .

Click to see all the text

GRÉGOIRE, F., 2002. Quebec North Shore herring (Division 4S). Science, Stock Status Report, B4-02, 8 p .

Click to see all the text

GRÉGOIRE, F., 2002. Atlantic mackerel of the Northwest Atlantic - Update (2001). Science, Stock Status Report, B4-04, 8 p .

Click to see all the text

GRÉGOIRE, F., L. LEFEBVRE, M. BEAUDOIN, 2002. Mise à jour des débarquements et des données biologiques du hareng (Clupea harengus harengus L.) de la division 4S de l'OPANO ; Landings and biological data update for NAFO division 4S herring (Clupea harengus harengus L.). MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2002/019, 41 p .

Click to see all the text

The herring (Clupea harengus harengus L.) fishery on the North Shore of Quebec saw rapid expansion through the 1970s. From less than 80 t per year for the 1960-1970 period, landings attained an average annual value of 707 t between 1979 and 2000. Peaks of 1,075 t, 2,885 t and 1,394 t were reached in 1982, 1983 and 1987 respectively, but since 1994, the annual landings show a decreasing trend. The most important herring landings are concentrated in three unit areas, namely 4Sz, 4Sv, and 4Sw with average annual landings of 279 t, 153 t and 97 t. The main fishing gear used to catch herring is the gillnet with average landings of 503 t per year. Since 1984, the annual length frequencies for the spring spawners sampled in unit area 4Sz have been characterised by the presence of three strong year-classes. These year-classes have been those of 1980, 1990 and 1994. For the fall spawners sampled in unit areas 4Sv and 4Sw, they have been those of 1979, 1991 and 1992. The Quebec North Shore herring is a regular catch of a groundfish and shrimp (Pandalus borealis) abundance research survey. This survey is conducted annually throughout the northern Gulf of St. Lawrence. During these surveys, herring catches are generally distributed throughout the sampled area. However, during the last years, more catches have been realised in the area located to the East Coast of Anticosti Island. Given the size of the region and the current catch level relative to other regions of Eastern Canada, herring catches on the North Shore of Quebec could certainly be higher. However, the information presently available does not allow us to accurately determine the level to which catches might be raised.

RINGUETTE, M., M. CASTONGUAY, J.A. RUNGE, F. GRÉGOIRE, 2002. Atlantic mackerel (Scomber scombrus) recruitment fluctuations in relation to copepod production and juvenile growth. Can. J. Fish. Aquat. Sci., 59: 646-656 .

A previous study identified relationships linking variations in the physical environment to fluctuations in zooplankton biomass and Atlantic mackerel (Scomber scombrus) recruitment. Diets of mackerel larvae were compared among four years, one of these years producing an exceptional year-class (1982). Comparisons were standardized for larval length and time of day. Stomach fullness differed significantly among years, with highest values observed in 1982. Stomach content wet weights were significantly larger in 1982 than in 1987 and 1996. The mean weight of Calanus finmarchicus nauplii prey in the diet was also significantly greater in 1982 than in 1985, 1987, or 1996. Female C. finmarchicus were more abundant and more widely distributed in the southern Gulf of St. Lawrence in 1982 compared with 1985, 1987, and 1990. These findings are consistent with the hypothesis of a link between production of copepod nauplii, feeding of mackerel larvae, and recruitment success. However, mackerel size at the end of the first year, as measured on otoliths, varied significantly between years and was smallest in 1982. Hypotheses are proposed to account for the coupling between high larval food abundance, small juvenile growth, and strong cohorts.

GRÉGOIRE, F., 2002. Maquereau bleu du nord-ouest de l'Atlantique - Mise à jour (2001). Rapport sur l'état des stocks, B4-04, 9 p .

Click to see all the text

GRÉGOIRE, F., 2001. Exploratio : informations concernant la biologie et la pêche du maquereau bleu (Scomber scombrus L.) présent dans cette région ; Oil and gas exploration off Cape Breton Island : informations concerning the biology and fishery of the Atlantic mackerel (Scomber scombrus L.) present in this area. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2001/114, 51 p .

Click to see all the text

The southern Gulf of St. Lawrence is the main spawning area for Atlantic mackerel (Scomber scombrus L.) in Canadian waters. Since 1983, a plankton-sampling survey has been conducted in this area for the primary purpose of estimating mackerel abundance by their eggs production. In the Maritimes and Quebec, mackerel are fished commercially from May to November. The largest landings are also made in the southern Gulf of St. Lawrence and around Cape Breton Island. Each year, mackerel landings are sampled in each of the main landing ports. These data, like those from the abundance surveys and the commercial landings, have been used to describe the distribution of mackerel in the vicinity of Cape Breton Island. This area could soon become a target for oil exploration. If it does, then the information in the present report could potentially be used in studies to measure the possible impacts of oil exploration and even possible future oil and gas extraction in this area.

GRÉGOIRE, F., 2001. Maquereau bleu du nord-ouest de l'Atlantique. Rapport sur l'état des stocks, B4-04, 12 p .

Click to see all the text

GRÉGOIRE, F., 2001. West coast of Newfoundland Atlantic herring (Division 4R) - Update (2000). Science, Stock Status Report, B4-01, 4 p .

Click to see all the text

GRÉGOIRE, F., 2001. Atlantic mackerel of the Northwest Atlantic. Science, Stock Status Report, B4-04, 12 p .

Click to see all the text

GRÉGOIRE, F., 2001. Hareng de la côte ouest de Terre-Neuve (division 4R) - Mise à jour (2000). Rapport sur l'état des stocks, B4-01, 4 p .

Click to see all the text

GRÉGOIRE, F. (éd.), 2000. Le maquereau bleu (Scomber scombrus L.) des sous-régions 2 à 6 de l'OPANO ; The Atlantic mackerel (Scomber scombrus L.) of NAFO subareas 2 to 6 ; The Atlantic mackerel (Scomber scombrus L.) of NAFO subareas 2 to 6. MPO, Secrétariat canadien pour l'évaluation des stocks, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2000/021, 473 p .

Click to see all the text

This document has been written to present the most recent data on the Atlantic mackerel (Scomber scombrus L.), including the fishery for this species, the assessment of its abundance, and certain research projects concerning it. A highly migratory, warm-water species, the Atlantic mackerel is the target of a commercial fishery that takes place along the coast of New England in winter and extends to the mackerel’s spawning and feeding grounds which, in Canadian waters, are located chiefly in the Gulf of St. Lawrence. It is also in this location, and more specifically in the southern part of the Gulf, that an abundance survey has been conducted by means of egg sampling. The commercial mackerel fishery is essentially an inshore fishery, and its importance can be measured by the very large number of fishermen who participate in it. The main types of gear used by fishermen in the Maritime provinces and Quebec are gillnets, lines, traps, purse seines, and weirs. Foreign vessels engage in an offshore fishery on the Scotian Shelf, but the importance of this fishery has greatly diminished since the 1977 introduction of a 200 nautical mile economic exclusion zone. Chapters 1 to 3 of the present document update the data on and describe the mackerel catches made over the past several years by Canadian and foreign fishermen in Canadian and U.S. waters. Chapter 4 of this document presents the main criteria for identifying the mackerel eggs sampled in the abundance surveys in the southern Gulf. Chapter 5 provides a detailed assessment of the mackerel’s abundance based on the egg samples from the 1998 survey. Chapter 6 proposes a method for calculating the variance and the confidence intervals for these abundance estimates. Over the past few years, various research projects have been carried out to improve mackerel abundance estimates. One of these methods, presented in Chapter 7, consists in using kriging to determine the average densities of eggs per unit area. Another project, described in Chapter 8, presents the results of the Daily Fecundity Reduction Method (DFRM). This method can be used to calculate spawning biomass not from annual egg production figures, which is the traditional approach, but rather from daily production figures. Some research projects have also been carried out in co-operation with the industry, and Chapter 9 presents the preliminary results of an exploratory survey in which mackerel eggs were sampled from a fishing vessel in St. Margaret’s Bay in Nova Scotia. Chapter 10 presents updated Canadian catch at age figures for Atlantic mackerel for the period 1990 to 1998. Lastly, Chapter 11 presents the main results for the 1999 Atlantic mackerel fishing season.

GRÉGOIRE, F., 2000. Atlantic Mackerel of the Northwest Atlantic. Science, Stock Status Report, B4-04, 10 p .

Click to see all the text

GRÉGOIRE, F., 2000. Maquereau bleu du nord-ouest de l'Atlantique. Rapport sur l'état des stocks, B4-04, 11 p .

Click to see all the text

BERNIER, D., ALDOUS, D., F. GRÉGOIRE, 2000. Conditions printanières de température et de salinité en relation avec la migration du maquereau bleu (Scomber scombrus L.) ; Spring temperature and salinity conditions in relation to the migration of Atlantic mackerel (Scomber scombrus L.). Rapp. can. ind. sci. halieut. aquat. ; Can. Ind. Rep. Fish. Aquat. Sci., 253, 44 p .

Click to see all the text

[Abstract only available in French]
Un relevé effectué conjointement avec le CRP, le Ministère des Pêches et de l'Aquaculture de la Nouvelle-Écosse et le Ministère des Pêches et des Océans du Canada (MPO) a été réalisé sur le banc de Georges au cours de la période du 5 au 7 mai 1998 inclusivement. L'objectif principal était de décrire certaines conditions environnementales présentes à cet endroit à un moment de l'année qui coïncide avec le retour du maquereau en eaux canadiennes. Des profils de température et de salinité ont été réalisés à 66 stations distribuées dans la région du banc de Georges. L'analyse de ces profils a démontré la présence dans la colonne d'eau de conditions thermiques différentes selon la zone échantillonnée. Les stations localisées sur le banc de Georges possédaient des conditions thermiques favorables à la présence du maquereau contrairement aux stations localisées sur sa périphérie. Lors de la migration printanière, le maquereau pourrait alors emprunter un ou des corridors de migration le détournant de cette région. Les prises accessoires de maquereau réalisées par des chalutiers, à l'extérieur du banc de Georges, à la même période que le relevé, semblent appuyer cette hypothèse.

GRÉGOIRE, F., 1999. Capelin of the Estuary and Gulf of St. Lawrence. Science, Stock Status Report, B4-03, 9 p .

Click to see all the text

GRÉGOIRE, F., Y. SAMSON, J.-L. BEAULIEU, 1999. Résultats du relevé exploratoire d'hydroacoustique au capelan (Mallotus villosus) réalisé sur la côte ouest de Terre-Neuve en 1998. MPO, Secrétariat canadien pour l'évaluation des stocks, Document de recherche ; 99/10, 20 p .

Click to see all the text

A capelin exploratory acoustic survey was conducted in 1998 on the west coast of Newfoundland. Between June 6 and June 10, 29 transects were completed and schools of fish were detected in each occasion. The schools were characterized by different geometries and those believed to be capelin were located between the thermoclin and the surface. It was not possible to determine the exact composition of these schools by the acquisition of commercial fish samples because the spawn and the fishery, which is directed essentially on mature females, were not started yet at the time of the survey.

GRÉGOIRE, F., C. LÉVESQUE, G. POIRIER, C. LEBLANC, 1999. Prises et débarquements de capelan (Mallotus villosus) dans l'estuaire et le golfe du Saint-Laurent en 1998 ; Capelin (Mallotus villosus) catches and landings in the Estuary and Gulf of St. Lawrence for 1998. MPO, Secrétariat canadien pour l'évaluation des stocks, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 99/09, 84 p .

Click to see all the text

In 1998, capelin landings in NAFO (Northwest Atlantic Fisheries Organization) Division 4RST were 9,077 t, an increase of a little over 1,200 t from 1997. This rise is due largely to catches of some 800 t made in course of an exploratory pair-trawl fishery in Chaleurs Bay. As in recent years, most of the 1998 capelin landings were made on the west coast of Newfoundland, where the purse seine season started without the delays that had characterized the early nineties. The year-by-year decline in fish size that had also been a major feature of this fishery has not been observed since 1996. Though capelin are still found in the southern Gulf of St. Lawrence, the recent expansion of the species in this area seems to have halted in 1998. The two abundance indices claculated from the catches of a bottom trawl abundance survey yield values that have been decreasing since 1996; in fact, the mean weights of the capelin catch per two for 1998 were among the lowest calculated since 1990. However, these values are difficult to interpret because of the uncertainty surrounding this type of survey as a means of assessing the abundance of a pelagic species such as capelin. The capelin is undoubtedly one of the most important forage species in the St. Lawrence Estuary and Gulf, and annual capelin consumption by its main predators is estimated at over a million tons. Mortality is very high, due mainly to predation and spawning activities. Fishing has little impact on abundance variation in the species. Given a certain lack of biological knowledge, the absence of an abundance survey directed at the species and capelin's key role in the marine ecosystem, any increase in catches aver the next few years should be gradual.

GRÉGOIRE, F., R.H. CRAWFORD, G. MOREAULT, G. MYRA, R. CONRAD, 1999. Maturité à la longueur et à l'âge chez le maquereau bleu (Scomber scombrus L.) échantillonné dans la baie St. Margarets en Nouvelle-Écosse en 1996 ; Maturity at length and age in Atlantic mackerel (Scomber scombrus L.) sampled in St. Margarets Bay, Nova Scotia, in 1996. Rapp. tech. can. sci. halieut. aquat. ; Can. Tech. Rep. Fish. Aquat. Sci., 2278, 45 p .

Click to see all the text

Sexual maturity curves at length and age for Atlantic mackerel (Scomber scombrus L.) were determined from biological sampling conducted in 1996 in St. Margarets Bay, Nova Scotia. Median lengths at maturity (L₅₀) were estimated at 299 mm and 269.6 mm for females and males respectively. These values are greater than the current legal minimum catch length. Mackerel reach sexual maturity very early, and by the age of four years all individuals are mature. The ovaries of small females were subjected to histological examination to check sexual maturity. The examination revealed that there were vitellogenic oocytes in some of them. Occurrence of such oocytes does not necessarily mean that they will be spawned in the course of the season, as several instances of mass atresia were observed. Analysis of the St. Margarets Bay samples also showed that mackerel migrate rapidly in this region and that size declines over the fishing season.

GRÉGOIRE, F., 1999. Capelan de l'estuaire et du golfe du Saint-Laurent. Rapport sur l'état des stocks, B4-03, 9 p .

Click to see all the text

GRÉGOIRE, F., M. DÉRASPE, 1998. Débarquements commerciaux et saison de ponte du maquereau bleu (Scomber scombrus L.) aux Îles-de-la-Madeleine et dans la baie des Chaleurs. Rapp. tech. can. sci. halieut. aquat., 2252, 41 p .

Click to see all the text

In Magdalen Islands, a reduction in the catches of mackerel from the spring gillnet fishery has been observed for the last few years. During the same time, a gradual delay was the main characteristic of the gillnet fishery in baie des Chaleurs. This catch reduction and delay in the fishing activities could be related to a decrease in the abundance and/or to a modification in the mackerel migration routes. The spring gillnet fishery is performed before and during the mackerel spawning season. The analysis of the seasonal evolution of the gonadosomatic index reveals that this spawning season in generally ended towards the beginning of August. During the fall, mackerel in Magdalen Islands are also the object of an important line fishery. For the moment, the level of the spring catches by gillnet does not seem to influence the level of those made during the fall. Line is less selective than gillnet and also responsible for the catch of mackerel of smaller size. Examination of the length frequencies of mackerel caught by line shows that it could have been possible to predict, at least in two occasions, the coming of a strong year-class before its full recruitment in the fishery.

GRÉGOIRE, F., D. GILBERT, 1998. La pêche au maquereau bleu (Scomber scombrus L.) dans les sous-régions 2 à 6 de l'OPANO pour 1997 ; The 1997 Atlantic mackerel (Scomber scombrus L.) fishery in NAFO subareas 2 to 6. MPO, Secrétariat canadien pour l'évaluation des stocks, Document de recherche ; DFO, Canadian Stock Assessment Secretariat, Research Document, 98/98, 49 p .

Landings of Atlantic mackerel (Scomber scombrus L.) in the northwest Atlantic totalled 35,050 t in 1997. Of this volume, 16,475 t were taken in NAFO subareas 5 and 6 and 18,575 t in subareas 3 and 4. In the latter subarea, the highest catches were made in divisions 4T, 4X and 4R, with landings of 13,909 t, 1,985 t and 1,140 t respectively. The biggest landings were made on Prince Edward Island and in Quebec, with values of 6,111 and 5,442 t. The most important unit areas were 4Tf, 4Tl and 4Tg in division 4T and unit areas 4Rc and 4Xm in divisions 4R and 4X. Over 8,500 t were caught using handlines and jigs, close to 6,000 t by gillnets and approximately 3,000 t using traps. The three largest year-classes, or cohorts, were, in descending order, those of 1995, 1994 and 1996. They alone accounted for 62 % of all catches. The dominant cohort of 1988 was still present in 1997 and represented 8.51 % of the catches. As in recent years, the main comments made by the industry concerned the large regional year-to-year variations in mackerel landings. In the case of the seine fishing off the west coast of Newfoundland, water temperature seems to play a significant role in these variations.

GRÉGOIRE, F., 1998. Débarquements commerciaux et prises accessoires de baudroie (Lophius americanus) et de grosse poule de mer (Cyclopterus lumpus) dans l'estuaire et le golfe du Saint-Laurent. Rapp. can. ind. sci. halieut. aquat., 243, 63 p .

Click to see all the text

Despite the fact that monkfish and lumpfish are considered as underexploited commercial species, or at least as the subject of an opportunist exploitation, a monitoring of them is realized on an annual basis by DFO. To that effect, three sources of information are used : the ZIFF files for the commercial landings, the data gathered on sea by observers, and finally the catches from the annual research surveys used to estimate the abundance of shrimp and groundfish. The data from the surveys have not allowed to pinpoint regions where the species could be found in great concentrations. Their presence was noted in only 1 % to 8 % of the sets covered by the observers. The most important catches are located on the north shore of the Gaspe Peninsula, the entrance of Chaleurs Bay, and on both sides of the Laurentian Channel at the exit of the Gulf of St. Lawrence. These areas mostly linked with the fisheries of cod, redfish, shrimp and Greenland halibut. The average yields are low and most of the time less than 10 kg/h. Eventually, a better picture of the status of these resources could be realized with fishing trials, along the coasts, during the spawning season.

CAMIRAND, R., F. GRÉGOIRE, 1998. L'évaluation de l'abondance du maquereau bleu du golfe du Saint-Laurent : des méthodes constamment améliorées. Naturaliste can., 122(2): 65-69 .

GRÉGOIRE, F., G. POIRIER, G. CHOUINARD, C. LÉVESQUE, 1997. Prises accessoires, débarquements et abondance du capelan (Mallotus villosus) dans l'estuaire et le golfe du Saint-Laurent ; Capelin (Mallotus villosus) by-catches, landings and abundance in the Estuary and Gulf of St. Lawrence. MPO, Secrétariat canadien pour l'évaluation des stocks, Document de recherche ; DFO, Canadian Stock Assessment Secretariat, Research Document, 97/122, 61 p .

Capelin landings in the Estuary and Gulf of St. Lawrence stood at 7,451 t in 1997, compared with 6,786 t for 1996. Most of this catch came from the west coast of Newfoundland. The fishing gears used for the majority of capelin catches are purse seine and trap on the west coast of Newfoundland, trap on the Lower North Shore of Quebec, and weir in the St. Lawrence Estuary. Analysis of daily landings shows that for a few years the opening of the fishery has progressively been delayed in certain unit areas. At the same time, a reduction in the mean size of the capelin has been observed. A reduction was also observed in 1997 for the two abundance indices calculated from by-catches in the shrimp and groundfish assessment survey. One of these indices, the occurrence percentage, nonetheless shows an upward trend, which means an expansion of the geographic range of capelin in the northern Gulf. An expansion of capelin distribution is also observed in the southern Gulf, as indicated by data from the groundfish assessment survey that is carried out there each year.

GRÉGOIRE, F., C. LÉVESQUE, J. HUDON, 1997. Description de la pêche au capelan (Mallotus villosus) dans l'estuaire et le golfe du Saint-Laurent pour 1996 ; Description of the capelin (Mallotus villosus) fishery in the Estuary and Gulf of St. Lawrence, 1996. MPO, Secrétariat canadien pour l'évaluation des stocks, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 97/15, 52 p .

Capelin landings in NAFO divisions 4RST stood at 6,509 t in 1996, with most of this catch coming from the purse seine fishery on the west coast of Newfoundland. In 1996, the management measure with respect to 50 capelin per kilo was eliminated; however, in exchange, TACs were reduced by 16 %. By-catches of capelin for shrimpers as a whole were an estimated 740 t. During the groundfish and shrimp assessment survey by the Alfred Needler in 1996, more capelin were caught than in previous years. The two abundance indices compiled from the survey, mean weight per set and occurrence percentages, reached maximum values. However, since the survey was not actually designed for pelagic fish like capelin, and since capelin is an important dietary item for some commercially valuable marine fish species, a cautious approach to harvesting the stock is still in order.

CASTONGUAY, M., M. LEVASSEUR, J.-L. BEAULIEU, F. GRÉGOIRE, S. MICHAUD, E. BONNEAU, S.S. BATES, 1997. Accumulation of PSP toxins in Atlantic mackerel : seasonal and ontogenic variations. J. Fish Biol., 50: 1203-1213 .

GRÉGOIRE, F., 1997. Capelan de l'estuaire et du Golfe du Saint-Laurent. Rapport sur l'état des stocks, B4-03, 7 p .

Click to see all the text

LÉVESQUE, C., F. GRÉGOIRE, 1997. Prises accessoires des chalutiers et distribution des larves de lançon (Ammodytes sp.) dans l'estuaire et le golfe du Saint-Laurent. MPO, Secrétariat canadien pour l'évaluation des stocks, Document de recherche, 97/121, 27 p .

Sandlance is a very important member of the marine ecosystem of the Estuary and Gulf of St. Lawrence. It is the prey of several species of marine fish, birds and mammals. Despite this importance, there is few data concerning its biology and the structure of the stocks. There is no direct fishery on this species but sandlance is a by-catch of the shrimp trawlers or those having fished for cod or redfish. These by-catches, gathered by the Observer Program between 1990 and 1997, and the larval abundance and distribution observed during the mackerel egg survey in the southern Gulf of St. Lawrence are described in the present document.

GRÉGOIRE, F., 1997. Analyses des captures à la longueur et évaluation du Rendement Maximal Soutenu pour le capelan de la Division de l'OPANO 4R ; Analyses of catch at length and evaluation of Maximum Sustainable Yield for capelin in NAFO Division 4R. MPO, Secrétariat canadien pour l'évaluation des stocks, Document de recherche ; DFO, Canadian Stock Assessment Secretariat, Research Document, 97/123, 49 p .

To evaluate the fishing effort associated with Maximum Sustainable Yield, Jones' Cohort Analysis Model and the Thompson and Bell Modified Yield Model were applied to annual catches at length from the capelin fishery on the west coast of Newfoundland. The main input parameters for these models are M, F and Z, which are defined as the instanteneous rates of natural, fishing and total mortality. The annual total mortality rates were derived using the following techniques : (1) the catch curve; (2) the Jones-van Zalinge equation; and (3) the Beverton-Holt equation. Certain Z values were selected and, with these held constant, different combinations of M and F were used in the cohort analysis. This analysis shows that, the higher the value ofF compared to M, the smaller the estimated biomass. However, the calculated yield does not vary. Moreover, for a fixed value of M and a variable Z, the Yield Model shows that the projected biomass tends to decrease slightly when F increases. This increase in F also results in a rapid increase in yield. Finally, the Yield Model shows that the current level of F is well below a value corresponding to Maximum Sustainable Yield.

GRÉGOIRE, F., J. LAMBERT, C. LÉVESQUE, M.-F. BEAULIEU, 1997. Évaluation de la biomasse du maquereau bleu (Scomber scombrus L.) pour 1996 par la Méthode de la Production Totale d'oeufs ; Assessment of the Atlantic mackerel (Scomber scombrus L.) biomass for 1996 by the Total Eggs Production Method. MPO, Secrétariat canadien pour l'évaluation des stocks, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 97/71, 29 p .

The 1996 survey to assess the Atlantic mackerel biomass began three days later than planned, on June 18. On the first set, surface water temperatures were noted to be higher than during the initial sets of previous surveys. Furthermore, eggs at later development stages and mackerel larvae were more numerous. Daily egg production for the two sets was evaluated at 0.6604 x 10¹³ and 0.6129 x 10¹³ eggs, with corresponding spawning biomass values of 259,842 t and 241,318 t. The biomass values fell to 211,023 t and 206,566 t when the egg densities at each station were corrected for the oversampling that occurs at the end of tows. When these corrected densities were applied in the geostatistical approach, daily production values of 0.6068 x 10¹³ and 0.6366 x 10¹³ eggs were obtained for the sets, yielding biomass values of 238,897 t and 250,628 t. Using this approach, it was also determined that there is a close relationship between egg density and water temperature. This relationship can be used to improve abundance estimates in the future. Because the timing of the survey and spawning were not well synchronized and owing to the method used to derive the seasonal egg production curve, the abundance estimate for 1996 should be considered a minimal value.

GRÉGOIRE, F., R. MORNEAU, H. BOUCHARD, J. LANDRY, 1997. Analyse des captures de capelan (Mallotus villosus) associées aux programmes Pêcheur-Repères du capelan et de la crevette (Pandalus borealis). MPO, Secrétariat canadien pour l'évaluation des stocks, Document de recherche, 97/14, 30 p .

In 1996, 39 % to 63% of the catches made by the capelin fishermen from the Index-Fisherman program were not landed. The most important reasons cited for the discards were the small number of females in the catches and also their small size. The profile of the daily catches suggests a variable availability of the capelin to the fishery. The fishing season is short, just the time of the spawn because the market is directed to the ovigerous female. Fishermen from the shrimp Index program caught less capelin in 1996 than during the previous years. It has been suggested that the gradual movement of their fleet towards the south of the Gulf of St. Lawrence explains this reduction.

GRÉGOIRE, F., 1997. Évaluation de la méthode de la réduction journalière de la fécondité pour estimer la biomasse du maquereau bleu (Scomber scombrus L.) ; An evaluation of the Daily Fecundity Reduction Method for estimating the biomass of Atlantic mackerel (Scomber scombrus L.). MPO, Secrétariat canadien pour l'évaluation des stocks, Document de recherche ; DFO, Canadian Stock Assessment Secretariat, Research Document, 97/84, 43 p .

The daily fecundity reduction method was evaluated to determine whether this approach can be used to estimate the spawning biomass of the Gulf of St. Lawrence mackerel. One of the key advantages it offers is that the biomass is calculated from the estimate of daily egg production rather than estimate of total annual egg production. Hence, there is no need to use or make an assumption about the shape of the seasonal egg production curve. Furthermore, since the method is based on the reduction in fecundity that occurs during the spawning season, an underestimation will not result even if the egg survey does not coincide the spawning, as sometimes happens with the total or annual egg production method which is currently in use. No major obstacles were encountered in using this method with mackerel. The spawning biomasses obtained for the two sets of the 1996 survey were 442,609 t and 554,063 t respectively. These values are higher than those obtained with the current method, which does not contain a correction for the fact that spawning was already well under way when the 1996 survey began. In view of the results, this method will be applied again during the next egg survey, planned for summer 1998. It may subsequently be adopted as the standard method for calculating the biomass of the Gulf of St. Lawrence mackerel.

GRÉGOIRE, F., 1997. Atlantic mackerel in the northwest Atlantic. Science, Stock Status Report, B4-04, 9 p .

Click to see all the text

GRÉGOIRE, F., 1997. Maquereau bleu du nord-ouest de l'Atlantique. Rapport sur l'état des stocks, B4-04, 10 p .

Click to see all the text

GRÉGOIRE, F., 1997. Description de la pêche au maquereau bleu (Scomber scombrus L.) pour la saison 1996 ; Description of the Atlantic mackerel fishery (Scomber scombrus L.) for the 1996 season. MPO, Secrétariat canadien pour l'évaluation des stocks, Document de recherche ; DFO, Canadian Stock Assessment Secretariat, Research Document, 97/85, 70 p .

Mackerel landings for the entire northwest Atlantic totalled 32,752 t in 1996, an increase of just over 5,000 t from 1995. This increase can be explained by the higher catches made by commercial fishers in the United States. Canadian landings were 17,710 t in 1996, compared with 17,706 t in 1995, and remained below the mean annual catch level of 20,000 t recorded for the period 1965 to 1995. The three NAFO divisions with the largest landings were 4T, 4R and 4X, with 10,004 t, 3,175 t and 1,899 t respectively. Landings are reviewed by gear type, statistical district and fishing community for the period 1985 to 1996. A similar analysis is presented for the catches in the Sydney area on the east coast of Cape Breton, where dredging operations were carried out in 1996. In 1996, the catch at age for the Canadian fishery was cominated by the 1994 and 1993 year-classes, which made up nearly 40 % of all catches. The U.S. abundance index still showed an upward trend in 1996. the mean catch per tow and mean weight per tow in 1996 represented the second highest values in the entire time series. Mackerel catch data from the different sources are compared, that is, from logbook and purchase slips, dockside monitoring operations and the Index Fishermen Program.

GRÉGOIRE, F., 1996. Capelin in the Gulf of St. Lawrence. DFO, Atlantic Fisheries, Stock Status Report, 96/25, 6 p .

BEAULIEU, J.-L., M. CASTONGUAY, M. LEVASSEUR, F. GRÉGOIRE, S. MICHAUD, E. BONNEAU, S.S. BATES, 1996. Rôle des toxines IPM (intoxication paralysante par les mollusques) dans une mortalité de maquereau bleu (Scomber scombrus) en Nouvelle-Écosse en 1993 ; Role of PSP (Paralytic Shellfish Poisoning) toxins in an Atlantic mackerel (Scomber scombrus) mortality in Nova Scotia in 1993. Rapp. can. ind. sci. halieut. aquat. ; Can. Ind. Rep. Fish. Aquat. Sci., 236, 17 p .

Click to see all the text

A mortality of Atlantic mackerel reported in Cape Breton in May 1993 prompted us to determine if paralytic shellfish poisoning (PSP) toxins could be identified as a potential cause of the kill. Live and dead mackerel collected in nearby traps had similar levels of PSP toxins in their livers. Additional mackerel were sampled from the commercial fishery in the southern and northern Gulf of St. Lawrence from June to October 1993. The total amount of PSP toxin per liver increased gradually with the age and the length of the fish, showing that mackerel bioaccumulate PSP toxins in their livers throughout their life. The quantity of PSP toxins per liver also increased during the summer, indicating that mackerel become comtaminated during their summer stay in the Gulf of St. Lawrence. By storing toxins in the liver, mackerel become potential lethal PSP vectors to their natural predators. However, eating mackerel poses no risk for humans as long as viscera are not consumed.

GRÉGOIRE, F., C. LÉVESQUE, 1996. Quelques résultats concernant les travaux en cours sur la fécondité en lots du maquereau bleu (Scomber scombrus L.). MPO, Pêches de l'Atlantique, Document de recherche, 96/61, 14 p .

Batch fecundity for the mackerel in the Gulf of St. Lawrence has been estimated in 1992 and 1993 at 69.05 and 50.80 eggs per gram of female. These results are similar to some values calculated for the mackerel in Europe. No value has been calculated in 1994 because most of the gonads didn't contain hydrated oocytes. Besides annual variations, it seems that batch fecundity shows also spatial variability. The results obtained in this study are preliminary and could be improved after an histological exam of the gonads.

GRÉGOIRE, F., 1996. Description de la pêche au maquereau bleu (Scomber scombrus L.) depuis 1985 et résultats préliminaires pour 1995 ; Description of the Atlantic mackerel (Scomber scombrus L.) fishery since 1985 and preliminary results for 1995. MPO, Pêches de l'Atlantique, Document de recherche ; DFO, Atlantic Fisheries, Research document, 96/59, 80 p .

Mackerel landings for the entire Northwest Atlantic in 1995 stand at 24,247 t so far, with Canadian catches totalling 14,568 t and US commercial and recreational landings 8,391 t and 1,289 t. No commercial fishing was carried out by foreign vessels along the US coast in the winter. However, 56 t of mackerel was taken by two Cuban boats off the Scotian Shelf between April and July. The NAFO Divisions where the bulk of catches were made are 4T, 4X and 4R, for which landings of 6,574 t, 3,594 t and 2,760 t were recorded respectively. As in past years, traps, gillnets and purse seines were the main fishing gear used. The Canadian catch at age in 1995 is characterized by an abundance of one- and two-year-olds, that is, the 1994 and 1993 year-classes. These year-classes represent respectively 24.50 % and 33.32 % of all catches made in 1995. As regards the 1994 year-class, such a large group of one-year-old mackerel has not been seen since the late 1960s. Finally, the landings recorded since 1985 are analysed, providing a more precise picture of where, when and how the largest catches of mackerel are made along the Canadian coastline.

GRÉGOIRE, F., S. HURTUBISE, 1996. Les prises accessoires de capelan (Mallotus villosus) dans le golfe du Saint-Laurent entre 1990 et 1995. MPO, Pêches de l'Atlantique, Document de recherche, 96/55, 59 p .

The present report describes the importance of the capelin catches in the shrimp and groundfish fisheries in the Gulf of St. Lawrence. The data used for the analyses were collected through the Observer program conducted in the Gulf between 1990 and 1995. The sampling coverage of this program is important so the results obtained can be considered representative of the entire fleets. In the shrimpers case, one estimates that the accidental catches of capelin range from 500 t to 600 t annually. Nordmore grid does not exclude all capelin, but at least reduces its catch. Other species are also caught with capelin. Some of them are strongly linked together.

GRÉGOIRE, F., G. BAKER, 1996. Commercial landings of Atlantic mackerel (Scomber scombrus L.) in Nova Scotia between 1985 and 1994. Can. Ind. Rep. Fish. Aquat. Sci., 237, 30 p .

Click to see all the text

The commercial landings of mackerel recorded for Nova Scotia and especially for the NAFO unit area 4Xm between 1985 and 1994 were analysed. Unit area 4Xm accounts for most of the mackerel landed in all Division 4X. Except in 1992 and 1994, when landings were larger, the average annual catch in this unit area was 2458 t, with a standard deviation of 348 t. Most of the landings were made in May, June, and July. In terms of landings, the two most important statistical districts of 4Xm, and in Nova Scotia as a whole, were 23 and 25. They cover the area between Shad Bay and the eastern shor of Mahone Bay. The primary landing harbours in District 23 were Hackett's Cove, Peggy's Cove, and West Dover, and in District 25 were New Harbour, Northwest Cove, Fox Point, Mill Cove, and Blandford. In spite of the consistent level of Canadian landings, the catches registered at various harbours sometimes exhibit substantial year-to-year fluctuations. While certain trends have been noted, it is generally impossible to predict the landings of a given location from those recorded at another location. Since all the observed fluctuations and trends cannot be caused solely by biomass variations, other factors must be involved. A review of the main factors is presented.

ARCHAMBAULT, D., F. GRÉGOIRE, 1996. Revue des données historiques de pêche du flétan atlantique du golfe du Saint-Laurent (Divisions de l'OPANO 4RST) (1893-1995). MPO, Secrétariat canadien pour l'évaluation des stocks, Document de recherche, 96/56, 43 p .

The landings of Atlantic halibut from the Gulf reached their lowest level ever seen in 1995, the reported catches of 83 t representing barely one quarter of the 300 t preventive TAC. The fishery in 1995 was similar to previous years : 1) most of the landings were made by Québec based vessels fishing in NAFO divisions 4S and 4T; 2) most of the fishery took place in the summer with fixed gears, longlines and gillnets. Since 1994, over twothirds of the landings (by weight/by numbers?) are composed of halibut less than 81 cm in length. In 1995, the proportion of these small fish has substantially increased in the landings of shrimp trawls and gillnets. However, the size and age compositions of halibuts remained broad. The young cohorts born in 1987-1989, clearly visible in 1994, are well represented in the landings of 1995. Although variable from year to year, growth rates of halibut in the Gulf is about 7.8 to 8.8 cm/year, being usually faster for the females.

GRÉGOIRE, F., 1996. Maquereau bleu du nord-ouest de l'Atlantique. MPO, Pêches de l'Atlantique, Rapport sur l'état des stocks, 96/24, 11 p .

GRÉGOIRE, F., 1996. Capelan du golfe Saint-Laurent. MPO, Pêches de l'Atlantique, Rapport sur l'état des stocks, 96/25, 6 p .

GRÉGOIRE, F., C. BELLEHUMEUR, 1996. Estimation géostatistique de la production quotidienne d'oeufs chez le maquereau bleu (Scomber scombrus L.) du golfe du Saint-Laurent. MPO, Pêches de l'Atlantique, Document de recherche, 96/60, 13 p .

The geostatistical approach was used on an exploratory basis to estimate the daily egg production for the Gulf of St. Lawrence mackerel. The variograms for the eggs densities in directions North-South and East-West clearly show that the data are spatially autocorrelated. The variograms also reveal a well defined spatial structure and a relatively low nugget effect in comparison with the variance of the data. The daily egg production was evaluated at 2.2561•10¹³ with lower and upper limits of 1.9438•10¹³ and 2.5683•10¹³ respectively. This estimation is improved in comparison with the estimations given by the classic statistical methods.

GRÉGOIRE, F., C. LÉVESQUE, H. BOUCHARD, 1996. La situation du capelan (Mallotus villosus) de l'estuaire et du golfe du Saint-Laurent en 1995. MPO, Pêches de l'Atlantique, Document de recherche, 96/54, 75 p .

Because of the fishery closure, the 1995 capelin landings for the Estuary and Gulf of St. Lawrence were only 152 t. More than 50 % (90 t) of these landings were fished in Division 4S only. A lateness in the beginning of the season is observed in unit areas 4Sw and 4Rc during the last years. During the same period of time, there is also a reduction in the capelin size which is expressed in fact by an increase in the number of capelins per kilogram. This value is also a selective criterion used by the Japanese market for the ovigerous female. The spatial distribution of the capelin catches made during the shrimps and groundfish survey of 1995 looks the same as the past distributions. Mean weight by set, as the frequency of occurrence for the past winter Gadus Atlantica surveys and Alfred Needler summer surveys show a decreasing trend. The highest mean weight by set is observed in Division 4S. The interpretation of these indices should be made with caution because they come from bottom trawls surveys which are not necessarily appropriate for a pelagic species like capelin. The monitoring of the most important spawning areas and acoustic surveys near these areas could be a more adequate way to calculate a capelin index of abundance.

GRÉGOIRE, F., 1996. Mackerel in the northwest Atlantic. DFO, Atlantic Fisheries, Stock Status Report, 96/24, 10 p .

GRÉGOIRE, F., P. CHEVRIER, M.-N. CROTEAU, C. LÉVESQUE, 1995. Sélectivité des filets maillants dans la pêche au maquereau bleu (Scomber scombrus L.). II, Îles-de-la-Madeleine. Rapp. can. ind. sci. halieut. aquat., 234, 25 p .

Click to see all the text

A selectivity of the gillnets used in a mackerel (Scomber scombrus) fishery in Magdalen Islands was performed using the Sechin model. This model was chosen because it considers, in the calculation of the selectivity, not only the length of fish but also the shape of its body, its compressibility at the retention point and the elasticity of the netting material. The shape of the body is expressed by girth measurement made at different points between operculum and dorsal fins, i.e. in the region where the fish is more likely to be caught. All the 3002 fish sampled had a net mark. The variation of the position of the mark is linked with the length of the fish caught. When the length decreases, the mark moves from the opercular region to the dorsal fins region. With the exception of the 2 7/8" mesh size, an increase of the mesh size is expressed by an increase of the mode, the range length and the maximal efficiency of the selectivity curves. For gillnets having a mesh size of 2 3/4", 3" and 3 1/4", modes were 348 mm, 362 mm and 388 mm respectively. Wear and other factors are suggested to explain the difference observed in the 2 7/8" mesh size case.

GRÉGOIRE, F., C. HUARD, M.-N. CROTEAU, C. LÉVESQUE, 1995. Sélectivité des filets maillants dans la pêche au maquereau bleu (Scomber scombrus L.). I, Baie des Chaleurs. Rapp. can. ind. sci. halieut. aquat., 233, 36 p .

Click to see all the text

Girth and length measurements were taken on 5,203 mackerels to describe, according to Sechin's model, the selectivity of the drifting gillnets used in Baie des Chaleurs. The highest maximum efficiency is observed for mesh size of 2 3/4" and the length of maximum efficieny is higher for welded mesh of size 2 7/8" than knotted mesh of the same size.

GRÉGOIRE, F., D. D'AMOURS, C. LÉVESQUE, D. THIBEAULT, 1995. Estimation de la biomasse reproductrice du stock de maquereau (Scomber scombrus L.) du golfe du Saint-Laurent pour 1994 ; Estimation of the Gulf of St. Lawrence spawning stock biomass of mackerel (Scomber scombrus L.) for 1994. MPO, Pêches de l'Atlantique, Document de recherche ; DFO, Atlantic Fisheries, Research Document, 95/118, 81 p .

The spawning biomass of mackerel, which spawn in the Gulf of St. Lawrence, was estimated at 800,676 t in 1994. This figure is slightly higher than the 1993 and 1992 estimates of 775,716 t and 791,953 t respectively. Egg samples taken with a pump were used to calculate a rate constant k of 0.17; this estimate was utilized in an exponential model to describe the vertical distribution of eggs. Until this point, a rate constant k of 0.15, extracted from the literature, had been used in a model to correct for the oversampling of eggs that occurs at the end of each tow. No relationship was observed between wind speed and k. This may be due to the small number of stations sampled and the response time of the water mass to changes in wind speed during sampling.

GRÉGOIRE, F., S. HURTUBISE, D. ARCHAMBAULT, R. MORNEAU, H. BOUCHARD, 1995. Analyses des données de pêche et de recherche sur le capelan (Mallotus villosus) du golfe du Saint-Laurent. MPO, Pêches de l'Atlantique, Document de recherche, 95/55, 64 p .

Annual landings of capelin in Divisions 4RST remained stable and inferior to 2,000 t until 1977. The new market for ovigerous females is responsible for the recent increase. Landings increased to almost 10,000 t in 1978, 1979 and 1989 and have remained at over 6,000 t since then. During the last two years, the most significant subdivisions in terms of landings were 4Rc, 4Sw and 4Tp. Only two or three age groups dominate capelin catches by age in Division 4R. Also in this division, catches by length indicate a decrease in the size of male and female capelin caught over the last few years. Capelin bycatch during winter groundfish assessment surveys was especially significant in the Esquiman Channel. During summer surveys, capelin were caught all over the northern Gulf. However, greater concentrations were ovserved west and east of Anticosti Island and on the west coast of Newfoundland. At present, on account of limited resources, there are not sufficient data to carry out an assessment of capelin biomass in the Gulf. In the meantime, further study could be conducted on the capelin data obtained during annual groundfish and shrimp assessment surveys.

GRÉGOIRE, F., J.-J. MAGUIRE, 1995. Description de la pêche au maquereau bleu (Scomber scombrus L.) en 1994 et essai d'application de ICA ; Description of the 1994 Atlantic mackerel (Scomber scombrus L.) fishery and trial application of ICA. MPO, Pêches de l'Atlantique, Document de recherche ; DFO, Atlantic Fisheries, Research Document, 95/111, 115 p .

In 1994, commercial landings of mackerel for the entire northwest Atlantic were roughly 25,000 t. According to the quota report, Canadian landings amounted to 19,000 t, which compares with 12,474 t based on the preliminary catch file established from logbook and purchase slip data. U.S. commercial and recreational landings stood at 5,000 t and 500 t, respectively. On the Scotian Shelf, a total of 44 t of mackerel was caught by Canadian and foreign vessels, with most of this quantity taken by a single Cuban boat. Among Canadian catches, the dominant year-classes were those of 1988, 1990, 1987 and 1991, in that order. The mean age and weight of these fish were 5.7 years and 533 g. A new technique was tested as a means of adjusting virtual population analysis (VPA) using abundance indices. This method, called Integrated Catch Analysis (ICA), was used with the egg index and a U.S. abundance index derived from a spring bottom trawl survey. With ICA, the spawning biomass and the total biomass of the northern population, which spawns mainly in the Gulf of St. Lawrence, and the southern population, which spawns chiefly along the U.S. coast, were estimated at 2 and 3 million tonnes, respectively. These estimates are similar to the figures obtained by some U.S. colleagues, who used a different method of calculation.

GRÉGOIRE, F., H. DIONNE, C. LÉVESQUE, 1994. Contenu en gras chez le maquereau bleu (Scomber scombrus L.) en 1991 et 1992. Rapp. can. ind. sci. halieut. aquat., 220, 79 p .

Click to see all the text

The fat content of mackerel (Scomber scombrus) in the Gulf of St. Lawrence changes greatly throughout the season. The lowest values are found at the beginning of the season, before the spawn, and the highest values during the fall. The fat content also changes with the size of the fish. For example, during the fall, the biggest fishes are also the fastest. The fat accumulation is faster for the biggest fishes in such a way that the difference in fat, between these fishes and mackerel of a lower size, increases during the season. There is no increase of the fat content for the immature fishes. On the other hand, there is an inverse relationship between fat and water contents. The fat and water contents sum increases with high values of fat content. Seasonal cycle of the fat content for the northern population is different from the southern population cycle. Minimum and maximum values are identical, except that there is a lag between the two cycles. The fat content could be helpful, at a certain specific time during the season, to recognize the population of origin.

GRÉGOIRE, F., M. SHOWELL, 1994. Description of the mackerel catches (Scomber scombrus L.) of the foreign fishery in NAFO divisions 4Vn, 4W and 4X between 1990 and 1992 ; Description des captures de maquereau (Scomber scombrus L.) de la pêche étrangère dans les divisions de l'OPANO 4Vn, 4W et 4X entre 1990 et 1992. Can. Data Rep. Fish. Aquat. Sci. ; Rapp. stat. can. sci. halieut. aquat., 947, 115 p .

Click to see all the text

Foreign vessels using bottom and semi-pelagic trawls are active off the coast of Nova Scotia. Various species are taken, including Atlantic mackerel (Scomber scombrus) in both a directed fishery and as a bycatch. From 1990 to 1992, mackerel catches totalled 3,636 t, 1,060 t and 2,284 t respectively. These catches were mainly characterized by the presence of young mackerel in the two and three-year age groups in 1990 and one to five in 1992. In the fall, mackerel are caught near the surface; however, the largest catches early in the season are taken at depths of about 100m. At this depth, there is a layer of water that is warmer than at the surface or the bottom, in which mackerel can be found at this time of the year. When mackerel was the target species or was present in a set, the other main species found were silver hake, herring, short-finned squid and dogfish. The presence of mackerel in this fishery as early as March and April and later in July and August in the regular commercial fishery confirms the year-round presence of mackerel in this region.

GRÉGOIRE, F., C. LÉVESQUE, 1994. Estimate of Gulf of St. Lawrence spawning stock of mackerel (Scomber scombrus L.) by total egg production and batch fecundity in 1993 ; Estimation du stock reproducteur de maquereau (Scomber scombrus L.) du golfe du Saint-Laurent par la production totale d'oeufs et la fécondité en lots en 1993. DFO, Atlantic Fisheries, Research Document ; MPO, Pêches de l'Atlantique, Document de recherche, 94/61, 22 p .

GREGOIRE, F., H. DIONNE, C. LÉVESQUE, 1994. Fat content of Atlantic mackerel (Scomber scombrus L.) in 1991 and 1992. Can. Ind. Rep. Fish. Aquat. Sci., 220, 69 p .

Click to see all the text

The fat content of mackerel (Scomber scombrus) in the Gulf of St. Lawrence changes greatly throughout the season. The lowest values are found at the beginning of the season, before the spawn, and the highest values during the fall. The fat content also changes with the size of the fish. For example, during the fall, the biggest fishes are also the fastest. The fat accumulation is faster for the biggest fishes in such a way that the difference in fat, between these fishes and mackerel of a lower size, increases during the season. There is no increase of the fat content for the immature fishes. On the other hand, there is an inverse relationship between fat and water contents. The fat and water contents sum increases with high values of fat content. Seasonal cycle of the fat content for the northern population is different from the southern population cycle. Minimum and maximum values are identical, except that there is a lag between the two cycles. The fat content could be helpful, at a certain specific time during the season, to recognize the population of origin.

GRÉGOIRE, F., J.-J. MAGUIRE, C. LÉVESQUE, 1994. Mackerel (Scomber scombrus L.) fishery situation in NAFO subareas 2-6 in 1993 ; Situation de la pêche au maquereau (Scomber scombrus L.) dans les sous-régions 2-6 de l'OPANO en 1993. DFO, Atlantic Fisheries, Research Document ; MPO, Pêches de l'Atlantique, Document de recherche, 94/62, 82 p .

GRÉGOIRE, F., 1993. Caractéristiques biologiques du maquereau bleu (Scomber scombrus L.) échantillonné le long des côtes canadiennes entre 1983 et 1991. Rapp. tech. can. sci. halieut. aquat., 1907, 137 p .

Click to see all the text

Data gathered by the sampling program of the commercial mackerel catches are used in the assessment of the status of this resource. These data are also analysed to improve our comprehension of the dynamic of this species. During the sampling period, it has been noted that the 1982 year-class was dominant in almost all the samples. This year-class is characterized by a greater number of males and by a smaller growth. The annual variations of some biological parameters are linked with the presence and the evolution of this strong year-class. Results presented here may be used in more theorical studies concerning the biology of this species.

GRÉGOIRE, F., 1993. Estimate of the spawning stock of mackerel (Scomber scombrus L.) in the Gulf of St. Lawrence and monitoring of catches for NAFO subareas 2-6 in 1992. DFO, Atlantic Fisheries, Research Document, 93/54, 75 p .

GRÉGOIRE, F., 1993. Biological characteristics of Atlantic mackerel (Scomber scombrus L.) sampled along the Canadian coast between 1983 and 1991. Can. Tech. Rep. Fish. Aquat. Sci., 1907, 137 p .

Click to see all the text

Data gathered by the sampling program of the commercial mackerel catches are used in the assessment of the status of this resource. These data are also analysed to improve our comprehension of the dynamic of this species. During the sampling period, it has been noted that the 1982 year-class was dominant in almost all the samples. This year-class is characterized by a greater number of males and by a smaller growth. The annual variations of some biological parameters are linked with the presence and the evolution of this strong year-class. Results presented here may be used in more theoretical studies concerning the biology of this species.

D'AUTEUIL, I., F. GRÉGOIRE, 1993. Description histologique du développement des ovocytes chez le maquereau bleu (Scomber scombrus L.) du golfe du Saint-Laurent. Rapp. tech. can. sci. halieut. aquat., 1912, 23 p .

Click to see all the text

The reproductive stock size of the Gulf of St. Lawrence mackerel is currently calculated using to the total egg production model. Female fecundity, one of the most important variables in this model, is determined as being the number of oocytes having a diameter greater than 140 µ just before spawning. This definition of the fecundity is inadequate for indeterminate serial spawners such as the anchovy and the mackerel. The batch fecundity method involves defining the fecundity of these fishes by multiplying the number of oocytes expelled per batch by the number of batches spawned during the spawning season. To determinate theses variables, the different phases in the development of the oocyte must be examined and described. In the case of the Gulf of St. Lawrence mackerel, an histological study was carried out on gonads gathered during the 1991 spawning season. The histological structures identified are similar to those observed with European mackerel. The oocyte size frequency distributions are multimodal with overlapping modes, which is characteristic of indeterminate serial spawners. The simultaneous presence of hydrated oocytes and post-ovulatory follicles was noted. Since the presence of empty follicles is an indication that spawning has started, gonads having these two structures at the same time should not be included in the calculation of the batch fecundity.

D'AUTEUIL, I., F. GRÉGOIRE, 1993. Histological description of oocyte development in Atlantic mackerel (Scomber scombrus L.) in the Gulf of St. Lawrence. Can. Tech. Rep. Fish. Aquat. Sci., 1912, 23 p .

Click to see all the text

The reproductive stock size of the Gulf of St. Lawrence mackerel is currently calculated using to the total egg production model. Female fecundity, one of the most important variables in this model, is determined as being the number of oocytes having a diameter greater than 140 µ just before spawning. This definition of the fecundity is inadequate for indeterminate serial spawners such as the anchovy and the mackerel. The batch fecundity method involves defining the fecundity of these fishes by multiplying the number of oocytes expelled per batch by the number of batches spawned during the spawning season. To determinate theses variables, the different phases in the development of the oocyte must be examined and described. In the case of the Gulf of St. Lawrence mackerel, an histological study was carried out on gonads gathered during the 1991 spawning season. The histological structures identified are similar to those observed with European mackerel. The oocyte size frequency distributions are multimodal with overlapping modes, which is characteristic of indeterminate serial spawners. The simultaneous presence of hydrated oocytes and post-ovulatory follicles was noted. Since the presence of empty follicles is an indication that spawning has started, gonads having these two structures at the same time should not be included in the calculation of the batch fecundity.

GRÉGOIRE, F., 1993. Estimation du stock reproducteur de maquereau (Scomber scombrus L.) du golfe du Saint-Laurent et suivi des captures pour les sous-régions 2-6 de l'OPANO en 1992. MPO, Document de recherche sur les pêches dans l'Atlantique, 93/54, 75 p .

In 1992, total catches of mackerel for the northwestern Atlantic were 38,893 t compared to 58,851 t in 1991.This reduction was especially caused by the halt to winter fishery activities in subareas 5 and 6. Canadian catches have remained stable over the years. In 1992, catches were 25,475 t, with the largest coming from divisions 4T, 4R, 4X and 4W with 7,657 t, 5,580 t, 4,788 t and 4,679 t respectively. Catches of 2,300 t were recorded along the Scotian Shelf by foreign vessels using mainly the midwater trawl. Most of the catches were made when mackerel was the main species sought. Most of the mackerel caught by this fishery were small. The 1988 year-class was, as in 1991, the dominant year-class. Total daily egg production for each pass was 3.4882 x 10¹³ and 1.4333 x 10¹³ eggs, yielding biomass estimates in the order of 1,466,803 t and 656,703 t. With the application of the correction for oversampled eggs at the surface, these values have been adjusted to 1,110,120 t and 473,787 t. In 1992, trap catches in Dingwall were 254 t. Dates on which 25, 50, 75 and 95 % of the total catches were made indicated that the migration occurred progressively earlier between 1983 and 1988 and later afterwards. During these two periods, total catches also decreased and increased gradually. The multiplicative model has been used successfully on the daily catch rates. Year and week explained 40 % of the variance of the catch rates, which have varied considerably since 1983, indicating that other variables apart from variations in abundance are responsible for fluctuations in trap catches. The increase in fat content was significant only for fish of a certain size which had already spawned. The water content of these fish decreased during the season. A linear regression is presented for determining fat content using water content, which is easier to calculate.

GRÉGOIRE, F., P. GAGNON, 1993. Analyse préliminaire des mesures de L1 sur des otolithes de maquereau bleu (Scomber scombrus L.) du golfe du Saint-Laurent. MPO, Document de recherche sur les pêches dans l'Atlantique, 93/62, 17 p .

We have observed in the Gulf of St. Lawrence mackerel some variations in the mean size of the otoliths at age one (L₁) among the most recent year-classes. No difference was observed for year-classes prior to 1977, when the stock biomass was much lower. The strong year-classes of 1982, 1987 and 1988 were signalled by sudden decreases of the mean value of L₁. We have also shown that fish with inferior or superior first-year growth relative to their group, as reflected by the L₁ measurement, tend to maintain their position afterwards.

GRÉGOIRE, F., 1992. Revue de la stratégie d'échantillonnage des oeufs utilisée lors des croisières d'évaluation de la biomasse reproductrice du maquereau bleu (Scomber scombrus L.) du golfe du St-Laurent. CSCPCA doc. rech., 92/52, 16 p .

GRÉGOIRE, F., 1992. Cycle de ponte, développement des ovocytes et résultats préliminaires concernant la fécondité en lots chez le maquereau (Scomber scombrus L.) du nord-ouest de l'Atlantique. CSCPCA doc. rech., 92/57, 45 p .

GRÉGOIRE, F., 1992. Suivi des captures de maquereau bleu (Scomber scombrus L.) en 1991 pour les sous-régions 2 à 6 de l'OPANO et évaluation de la biomasse reproductrice du golfe du Saint-Laurent. CSCPCA doc. rech., 92/53, 39 p .

D'AMOURS, D., F. GRÉGOIRE, 1992. Analytical correction for oversampled Atlantic mackerel (Scomber scombrus) eggs collected with oblique plankton tows. Fish. Bull., 90: 190-196 .

GREGOIRE, F, FITZGERALD, K., 1991. Analysis of Atlantic mackerel (Scomber scombrus L.) catch data gathered by a fisherman in Dingwall, Nova Scotia, from 1983 to 1990.. Can. Ind. Rep. Fish. Aquat. Sci., 210, 25 p .

Click to see all the text

An analysis of mackerel (Scomber scombrus) catch data collected between 1983 and 1990 for 3 traps owned by a fisherman in Dingwall (Nova Scotia), Mr. Kelly Fitzgerald, was conducted by the Maurice- Lamontagne Institute. The results indicate that the first mackerel was caught each year in late May. The beginning of each fishing season is marked, not by a gradual increase in catches, but rather by large mackerel catches. Catches and catch per unit effort have been on the decline since 1983. The fishing season in Dingwall is relatively short, around one month. No relationship was found between total annual catches or the length of the fishing season and the starting date of each season. The decrease in catch per unit effort could be explained by a change in the mackerel migratory pattern. Thermographs have been installed on the mackerel traps in order to determine the influcence of water temperature on the coastal migration of the mackerel.

GRÉGOIRE, F., A.F. SINCLAIR, 1991. Effets des vents côtiers sur les débarquements commerciaux de morues (Gadus morhua L.) par les engins fixes des unités statistiques 4Sv et 4Sw. Rapp. tech. can. sci. halieut. aquat., 1795, 54 p .

Click to see all the text

Spectral analysis performed between inshore cod landings and alongshore winds revealed a cause and effect relationship. Landings responded at a large spatial scale and at periods consistent with storm events. It was not possible to predict landings by the use of past landings and the wind as a transfer function. Winds do not explain the recent decrease of cod catches.

GRÉGOIRE, F., K. FITZGERALD, 1991. Analyse des données de captures de maquereaux bleus (Scomber scombrus L.) par un pêcheur de Dingwall, Nouvelle-Écosse, pour la période de 1983 à 1990. Rapp. can. ind. sci. halieut. aquat., 210, 19 p .

Click to see all the text

An analysis of mackerel (Scomber scombrus) catch data collected between 1983 and 1990 for 3 traps owned by a fisherman in Dingwall (Nova Scotia), Mr. Kelly Fitzgerald, was conducted by the Maurice-Lamontagne Institute. The results indicate that the first mackerel was caught each year in late May. The beginning of each fishing season is marked, not by a gradual increase in catches, but rather by large mackerel catches. Catches and catch per unit effort have been on the decline since 1983. The fishing season in Dingwall is relatively short, around one month. No relationship was found between total annual catches or the length of the fishing season and the starting date of each season. The decrease in catch per unit effort could be explained by a change in the mackerel migratory pattern. Thermographs have been installed on the mackerel traps in order to determine the influcence of water temperature on the coastal migration of the mackerel.

GRÉGOIRE, F., 1991. Étude des captures de maquereaux (Scomber scombrus L.) enregistrées aux trappes d'un pêcheur de Dingwall, Nouvelle-Écosse, pour la période comprise entre 1983 et 1990. CSCPCA doc. rech., 91/70, 19 p .

GRÉGOIRE, F., 1991. Analyse des captures de maquereaux bleus (Scomber scombrus L.) en 1990 pour les sous-régions 2 à 6 de l'OPANO et présentation de certaines caractéristiques biologiques. CSCPCA doc. rech., 91/78, 42 p .

ARMELLIN, A., M. CASTONGUAY, F. GRÉGOIRE, D.K. CAIRNS, 1990. Survey of Atlantic mackerel (Scomber scombrus) seine fishing in the southern Gulf of St. Lawrence. Can. Ind. Rep. Fish. Aquat. Sci., 202, 27 p .

Click to see all the text

In 1987, the Department of Fisheries and Oceans distributed a questionnaire to the 308 mackerel (Scomber scombrus) fishermen with seining licences from the southern Gulf of St. Lawrence in order to characterize their fishing activities. The percentage of questionnaires returned was 24.7 %. Other species exploited by mackerel fishermen include lobster, cod, and herring. Presence of mackerel in the area of activity of fishermen in the main factor determining fishing trips for mackerel. Economic considerations (mostly low prices) play an important role in the fishermen's lack of interest toward this resource. The largest landings per fisherman apparently occur in western Prince Edward Island. The main uses for mackerel landings are in decreasing order of importance plant processing, bait for personal use, and bait sold to plants.

ARMELLIN, A., M. CASTONGUAY, F. GRÉGOIRE, D.K. CAIRNS, 1990. Enquête sur la pêche au maquereau (Scomber scombrus) à la senne dans le sud du golfe du Saint-Laurent. Rapp. can. ind. sci. halieut. aquat., 202, 27 p .

Click to see all the text

In 1987, the Department of Fisheries and Oceans distributed a questionnaire to the 308 mackerel (Scomber scombrus) fishermen with seining licences from the southern Gulf of St. Lawrence in order to characterize their fishing activities. The percentage of questionnaires returned was 24.7 %. Other species exploited by mackerel fishermen include lobster, cod, and herring. Presence of mackerel in the area of activity of fishermen in the main factor determining fishing trips for mackerel. Economic considerations (mostly low prices) play an important role in the fishermen's lack of interest toward this resource. The largest landings per fisherman apparently occur in western Prince Edward Island. The main uses for mackerel landings are in decreasing order of importance plant processing, bait for personal use, and bait sold to plants.

CASTONGUAY, M., F. GRÉGOIRE, 1989. Le maquereau bleu (Scomber scombrus Linné) du nord-ouest de l'Atlantique, sous-régions 2 à 6 de l'OPANO : évaluation du stock en 1988. CSCPCA doc. rech., 89/39, 25 p .

GRÉGOIRE, F., M. CASTONGUAY, 1989. L'alimentation du maquereau bleu (Scomber scombrus) dans le golfe du Saint-Laurent et sur le plateau néo-écossais, avec une application du test de Mantel. Rapp. tech. can. sci. halieut. aquat., 1673, 23 p .

Click to see all the text

We analysed gut contents of 359 Atlantic mackerel (Scomber scombrus) collected in 1979 and 1980 over three seasons and in five areas of the Gulf of St. Lawrence and the Scotian Shelf. Generally, occurrence and numerical methods indicated that copepods (especially Temoridae), larvae, nematods, and decapods dominate the diet. A downward seasonal trend in prey diversity was also observed. Multivariate non parametric comparisons among areas, among seasons, and among three size classes of mackerel were performed using the Mantel test. Significant diet differences were found between all non-adjacent pairs of areas and between seasons, but not between size classes.

GRÉGOIRE, F., M. CASTONGUAY, 1989. Étude de dimensions au premier annulus d'otolithes de maquereau bleu (Scomber scombrus) du nord-ouest de l'Atlantique. Rapp. tech. can. sci. halieut. aquat., 1680, 15 p .

Click to see all the text

In the Northwest Atlantic, the first year of growth is about two months longer for the southern contingent of Atlantic mackerel than for the northern contingent. In order to develop a method to distinguish between mackerel of the two contingents, linear and surface dimensions of the first year of growth (first annulus) of 570 otoliths were compared between mackerel of the two contingents sampled in 1983. Although southern contingent mackerel had significantly larger dimensions (Wilcoxon test, P<0.01), distributions of dimensions greatly overlap between the two contingents, preventing the use of dimensions to distinguish the contingent of origin. When comparisons of dimensions were separated by year class, significant differences between the two contingents were only found for 3 and 10 year old mackerel (Wilcoxon test, P<0.05). The mean back-calculated length at one year of southerns contingent mackerel (222.8 mm) was significantly larger than that of northern contingent mackerel (207.4 mm) (t-test, P<0.001). Within each contingent, significant differences were found among back-calculated lengths at one year of different year classes (Anovas, P<0.01), although no trend was apparent.