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Bibliography of the Maurice Lamontagne Institute

Denis CHABOT

NELSON, J.A., D. CHABOT, 2011. General energy metabolism. Pages 1566-1572 in A.P. Farrell (eds). Encyclopedia of fish physiology : from genome to environment, volume 3. San Diego : Academic Press .

CHABOT, D., S. DUBÉ, 2011. Processus consultatif scientifique régional sur l'évaluation des stocks de crabe des neiges de l'estuaire et du nord du golfe du Saint-Laurent, 7 au 9 et 17 février 2011, Institut Maurice-Lamontagne ; Regional Science Advisory Process on the Assessment of the Estuary and Northern Gulf of St. Lawrence Snow Crab Stocks, February 7 to 9 and 17, 2011, Maurice Lamontagne Institute. MPO, Secrétariat canadien de consultation scientifique, Série des comptes rendus; DFO, Canadian Science Advisory Secretariat, Proceedings Series, 2011/018, 29 p .

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CHABOT, D., C. CYR, S. BRULOTTE, 2010. Compte rendu de la réunion du processus consultatif scientifique de la région du Québec portant sur l’examen du plan de suivi écologique de la ZPM Manicouagan. MPO, Secrétariat canadien de consultation scientifique, Série des comptes rendus; DFO, Canadian Science Advisory Secretariat, Proceedings Series, 2010/044, 20 p .

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DAOUD, D, Y. LAMBERT, C. AUDET, D. CHABOT, 2010. Size and temperature-dependent variations in intermolt duration and size increment at molt of Northern Shrimp, Pandalus borealis. Mar. Biol., 157: 2655-2666 .

Growth of Pandalus borealis post-larval stages was measured in relation to size and temperature. Growth characteristics, including intermolt period (IP), molt increment (MI) in size and mass, and tissue allocation in juvenile, male, and female shrimp, were evaluated at 2, 5, and 8 °C, the temperature range where this species is generally found in the Northwest Atlantic. Significant variations in growth were associated with temperature and shrimp size. IP (days) increased significantly with shrimp size and was inversely related to temperature. Size (cephalothorax length in mm) and temperature effects were best described by IP = 10(0.67 log(CL) – 0.06 T – 1.34). The pronounced effect of temperature on IP while MIS changed little indicated that the main influence of temperature on growth rate of P. borealis was through IP. Specific growth rate (SGRS) decreased rapidly with size to near zero values in females. Overall, juveniles were much more sensitive to temperature variations than adults, suggesting that temperatures encountered during the juvenile stage will largely influence the growth trajectory of the population.©2010 Springer

CHABOT, D., DUBÉ, S, 2010. Évaluation des stocks de pétoncle des eaux côtières du Québec, 26 janvier 2010, Institut Maurice-Lamontagne ; Stock assessments on scallop in the Quebec's inshore waters, January 26, 2010, Maurice Lamontagne Institute. MPO, Secrétariat canadien de consultation scientifique, Série des comptes rendus ; DFO, Canadian Science Advisory Secretariat, Proceedings Series, 2010/004, 16 p .

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MORISSETTE, L., M. CASTONGUAY, C. SAVENKOFF, D.P. SWAIN, D. CHABOT, H. BOURDAGES, M.O. HAMMILL, J. MARK HANSON, 2009. Contrasting changes between the northern and southern Gulf of St. Lawrence ecosystems associated with the collapse of groundfish stocks. Deep-Sea Res., Part II, Top. Stud. Oceanogr., 56(21-22): 2117-2131 .

In order to have a global view of ecosystem changes associated with the collapse of groundfish species in the Gulf of St.Lawrence during the early 1990s, Ecopath mass balance models were constructed in corporating uncertainty in the input data.These models covered two ecosystems (northern and southern Gulf of St.Lawrence; NAFO divisions 4RSand 4T), and two time periods (before the collapse, in the mid-1980s, and after it, in the mid 1990s). Our analyses revealed that the ecosystem structure shifted dramatically from one previously dominated by piscivorous groundfish and small-bodied forage species during the mid-1980s to one now dominated only by small-bodied pelagic species during the mid-1990s in both southern and northern Gulf.The species structure in the northern Gulf versus southern Gulf was different, which may explain why these two ecosystems did not recover the same way from the collapse in the early1990s. Productivity declined in the northern Gulf after the collapse but increased in the southern Gulf. The collapse of groundfish stocks resulted in declines in the mean trophic level of the landings in both the northern and the southern Gulf. Even though fishing mortality was then intentionally reduced, this part of the total mortality was taken up by predation.The temporal changes in the internal structure of both ecosystems are reflected in their overall emergent properties.©2009 Elsevier Ltd.

SAVENKOFF, C., S. VALOIS, D. CHABOT, M.O. HAMMILL, 2009. Input data and parameter estimates for ecosystem models of the northern Gulf of St. Lawrence (2003–2005). Can. Tech. Rep. Fish. Aquat. Sci., 2829, 123 p .

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Mass-balance models were used to reconstruct trophic flows through the whole northern Gulf of St. Lawrence ecosystem (NAFO divisions 4RS) for the 2003-2005 period. The whole-system model of the northern Gulf of St. Lawrence is divided into 31 functional groups or compartments from phytoplankton and detritus to marine mammals and seabirds, including harvested species of pelagic, demersal, and benthic domains. We present here details of the input data (biomass, production, consumption, export, and diet composition) for each compartment used for modelling. The parameter estimates from inverse modelling are also shown for comparison.

CHABOT, D., G. CLAIREAUX, 2008. Environmental hypoxia as a metabolic constraint on fish: the case of Atlantic cod, Gadus morhua. Mar. Pollut. Bull., 57(6-12): 287-294 .

Hypoxia is known to provoke a wide range of effects on aquatic animals. Here we use laboratory and field data on Atlantic cod, Gadus morhua, to illustrate that many of these responses can be explained within the metabolic scope (MS) framework, i.e. taking into account the directive and limiting effects of dissolved oxygen (DO) on the ability of animals to acquire energy for growth and activity. A MS model for cod shows that scope for activity (swimming, feeding, etc.) is proportional to DO and becomes nil, jeopardising survival, when DO is <≈20 % air saturation. Laboratory studies have confirmed this lethal threshold and demonstrated that growth and food ingestion were significantly reduced below 70 % sat. This loss of appetite has been linked to a reduction of the peak value and an increase in duration of postprandial metabolism, in agreement with the MS model. Dwindling MS during hypoxia imposes an upper limit to swimming performance. Cod may also opt to reduce spontaneous swimming activity to spare oxygen for other activities such as digestion. In the Kattegat, the Baltic Sea, and the Gulf of St. Lawrence, eastern Canada, cod completely avoid waters where their MS is near zero. Furthermore, cod density increases exponentially with DO up to ≈70 % sat in the Gulf of St. Lawrence. Although hypoxia results in other direct and indirect effects as well, the MS framework allows modelling of many of the responses to hypoxia for individual cod that ought to be reflected at the population and community levels. The MS framework is also useful to compare species responses. We show that the impact of hypoxia on MS is similar, when expressed as a proportion of MS in normoxia, in cod, European sea bass (Dicentrarchus labrax), the common sole (Solea solea) and turbot (Psetta maxima). Data are required for other species to evaluate how general these findings are.©2008 Elsevier Ltd.

CHABOT, D., B. SAINTE-MARIE, K. BRIAND, J.M. HANSON, 2008. Atlantic cod and snow crab predator-prey size relationship in the Gulf of St. Lawrence, Canada. Mar. Ecol. Prog. Ser., 363: 227-240 .

Atlantic cod Gadus morhua stomach contents (n = 30 973, including 28 377 non-empty stomachs) and morphometric measurements on live snow crab Chionoecetes opilio and cod were examined to assess the predator-prey relationship between these 2 species. The most common snow crab instars found in cod stomachs were III and V (˜6 to 8 and ˜12 to 16 mm carapace width [CW], respectively) in the northern Gulf of St. Lawrence (GSL) and VI and VII (˜17 to 23 and ˜23 to 31 mm CW, respectively) in the southern GSL. A significant positive relationship was found between cod length and the largest and smallest CW of snow crab ingested by cod. Positive relationships were also found between gape width and body length in cod and between 3 measures of size (maximum span, width at rest, length at rest) and CW in snow crab. Snow crab length at rest was closely related to cod gape width, suggesting that the largest snow crab ingested by cod must be attacked from the side. There appears to be a plateau at 65.1 mm in the relationship between maximum snow crab CW and cod length, caused by the absence of large (adolescent and adult) male snow crab in cod stomachs. Other studies have found recently moulted, soft-shell snow crabs in cod stomachs, but this appears to be rare. Thus, snow crabs are susceptible to predation by cod mostly for the first 4 yr of postsettlement in the GSL. Any effect of cod predation on the snowcrab fishery would be felt 6 to 11 yr later, given growth models established for the GSL.©2008 Inter-Research

SAVENKOFF, C., L. MORISSETTE, M. CASTONGUAY, D.P. SWAIN, M.O. HAMMILL, D. CHABOT, J.M. HANSON, 2008. Interactions between marine mammals and fisheries: implications for cod recovery FOR COD RECOVERY. Pages 107-151 in J. Chen & C. Guo (ed.). Ecosystem Ecology Research Trends. Nova Science Publishers .

Abundance of many Atlantic cod (Gadus morhua) and groundfish stocks in the Northwest Atlantic declined to low levels in the early 1990s, resulting in cessation of directed fishing for these stocks, thus ending one of the largest and longest running commercial groundfish fisheries in the world. The stocks of the northern (nGSL) and southern Gulf of St. Lawrence (sGSL) were closed to directed cod fishing from 1994 to 1996 for the nGSL and from 1993 to 1997 for the sGSL, followed by the opening of a small directed fishery in the two systems. In the northern Gulf of St. Lawrence, the ecosystem biomass structure shifted dramatically from one dominated by demersal fish predators (Atlantic cod Gadus morhua, redfish Sebastes spp.) and small-bodied forage species (capelin Mallotus villosus, mackerel Scomber scombrus, herring Clupea harengus, northern shrimp Pandalus borealis) to one now dominated by only small-bodied forage species. The decline of large predatory fishes has left only marine mammals as top predators during the mid-1990s, and marine mammals and Greenland halibut Reinhardtius hippoglossoides during the early 2000s. Large changes also occurred in the biomass structure and ecosystem functioning of the adjacent southern Gulf of St Lawrence (sGSL) but they were not as dramatic. Although predatory fishes decreased between the mid-1980s and mid-1990s, and prey consumption by seal species increased considerably, large cod remained among the most important single predators on fish in the sGSL. The changes in top-predator abundance driven by human exploitation of selected species resulted in a major perturbation of the structure and functioning of both Gulf ecosystems and represent a case of fishery-induced regime shift. Overfishing influenced community biomass structure directly through preferential removal of larger-bodied fishes and indirectly through predation release. Species interactions are central to ecosystem considerations. In marine ecosystems, predation can be the major ecological process affecting fish populations and piscivory is often the largest source of fish removal, usually larger than fishing mortality. In both northern and southern Gulf ecosystems, predation mortality exceeded fishing mortality for most groups in recent years because fishing mortality was intentionally reduced by fisheries closures. Seals have benefited from reduced hunting (harvesting and culling/bounties) since the 1970s. Consumption of fish by marine mammals exceeded consumption by predatory fishes in the two ecosystems in the recent time periods. Since the collapse of groundfish stocks, commercial fisheries and seals have become important predators on predatory fishes-possibly slowing their recovery. In recent years, consumption by seals shifted towards species at lower trophic level (forage fishes and invertebrates), which were also the main target of fisheries. Thus, commercial fisheries and seals may have become important competitors of predatory fishes for the same resource.©2008 Nova Science Publishers, Inc.

MORISSETTE, L., M. CASTONGUAY, C. SAVENKOFF, D.P. SWAIN, D. CHABOT, H. BOURDAGES, M.O. HAMMILL, J.M.HANSON, 2008. Contrasting changes between the northern and southern Gulf of St. Lawrence ecosystems associated with the collapse of groundfish stocks. Deep-Sea Res., Part II , Top. Stud. Oceanogr. [ARTICLE IN PRESS] .

In order to have a global view of ecosystem changes associated with the collapse of groundfish species in the Gulf of St. Lawrence during the early 1990s, Ecopath mass-balance models were constructed incorporating uncertainty in the input data. These models covered two ecosystems (northern and southern Gulf of St. Lawrence; NAFO divisions 4RS and 4T), and two time periods (before the collapse, in the mid-1980s, and after it, in the mid-1990s). Our analyses revealed that the ecosystem structure shifted dramatically from one previously dominated by piscivorous groundfish and small-bodied forage species during the mid-1980s to one now dominated only by small-bodied pelagic species during the mid-1990s in both southern and northern Gulf. The species structure in the northern Gulf versus southern Gulf was different, which may explain why these two ecosystems did not recover the same way from the collapse in the early 1990s. Productivity declined in the northern Gulf after the collapse but increased in the southern Gulf. The collapse of groundfish stocks resulted in declines in the mean trophic level of the landings in both the northern and the southern Gulf. Even though fishing mortality was then intentionally reduced, this part of the total mortality was taken up by predation. The temporal changes in the internal structure of both ecosystems are reflected in their overall emergent properties. ©2008 Elsevier Ltd.

MARION, A., M. HARVEY, D. CHABOT, J.-C. BRÊTHES, 2008. Feeding ecology and predation impact of the recently established amphipod, Themisto libellula, in the St. Lawrence marine system, Canada. Mar. Ecol. Prog. Ser., 373: 53-70 .

Themisto libellula was virtually absent from the St. Lawrence marine system (SLMS) before 1990. Since then, it has become an abundant, full-time resident of this system. Hyperiid amphipods of the genus Themisto are principally carnivorous and represent an essential link in the trophic pathway from secondary production to higher trophic levels. Sampling of T. libellula was carried out in the lower St. Lawrence Estuary (LSLE) and the northwest Gulf of St. Lawrence (NWGSL) in the fall of 1998, 2003 and 2004 to study the feeding dynamics and predation impact of this species on mesozooplankton and macrozooplankton communities. Our results showed that T. libellula was an opportunistic predator with a circadian feeding cycle; activity was higher during the second part of the night and the sunrise period. Stomach content analyses showed that these amphipods consumed chiefly copepods, in particular, the copepodite stages CIV and CV of Calanus finmarchicus. Euphausiids, chaetognaths, amphipods and mysids constituted other important prey. Digestion time was estimated at 13 h. The daily ingestion rate of T. libellula was estimated using 2 approaches: (1) stomach fullness index and (2) mean number of prey removed per unit of time and converted to prey biomass using the stage-species dry masses of each prey item. We found that the daily ingestion rate of T. libellula ranged from 6.32 to 16.82 % of body dry mass per day in both study areas (LSLE and NWGSL). Concerning predation impact, T. libellula consumed between 0.14 and 1.79 % of the combined mesozooplankton and macrozooplankton standing stock per day and between 0.43 and 2.48 % of the C. finmarchicus standing stock. Themisto libellula may thus exert a significant control on the mesozooplankton and macrozooplankton communities in the SLMS through direct predation.©2008 Inter-Research

CHABOT, D., D. GILBERT, 2008. The impact of hypoxia on cod from the Baltic and the Gulf of St. Lawrence. ICES CM 2008/J:15, 23 p .

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Both the Baltic Sea and the Gulf of St. Lawrence are characterised by low levels of dissolved oxygen (DO) below a halocline. When hydrographical conditions are favourable, salty oxygenated water from the North Sea flows into the deep basins of the Baltic. Between such events, oxygen levels are progressively depleted. During the last few decades, the frequency of inflows has decreased and eutrophication has increased oxygen consumption. As a result, young cod have been displaced to shallower waters whereas adult cod live in mid-water, on top of the most hypoxic or even anoxic water. Diet has changed and cod rely less on benthic prey, although it is not clear if this has resulted in a reduced energy intake. Worse, reproduction failure has become common as low salinity typical of the Baltic Sea surface water causes negative buoyancy in cod eggs, which sink into the severely hypoxic or anoxic deep waters and die. In the deep channels of the Gulf of St. Lawrence, water originating at the mouth of the Laurentian channel flows landward. DO averages 50-65 % sat. In the Cabot Strait and declines progressively towards the heads of the deep channels. Natural variability in the DO level at the mouth of the Laurentian Channel and possibly also eutrophication have resulted in a drop from about 40 % down to about 20 % sat. in the estuary. Cod have suffered habitat loss as a result, but the main impact appears to be a slowing of growth caused by a reduction of the metabolic scope.

CHABOT, D., A. RONDEAU, B. SAINTE-MARIE, L. SAVARD, T. SURETTE, P. ARCHAMBAULT, 2007. Distribution des invertébrés benthiques dans l'estuaire et le golfe du Saint-Laurent ; Distribution of benthic invertebrates in the Estuary and Gulf of St. Lawrence. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2007/018, 108 p .

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This study had two objectives. The first was to gather all the available data from scientific surveys both at the Maurice-Lamontagne Institute (MLI) and the Gulf Fisheries Centre (GFC) in order to establish distribution patterns and relative abundance of benthic invertebrates in the lower estuary and the gulf of St. Lawrence (LEGSL). The second objective was to propose Ecologically and Biologically Significant Areas (EBSAs) for benthic invertebrates of the LEGSL, according to these distribution and relative abundance data. Surveys from the MLI are mainly conducted in the lower estuary and in the northern gulf of St. Lawrence (nGSL) but some cover Gaspesie, including Chaleurs bay, and the Magdalen Islands. The southern gulf of St. Lawrence (sGSL) is covered by the GFC surveys. The bulk of the information presented here comes from annual scientific surveys carried out by the two regions: the multi-species survey and the mobile gear Sentinel survey by the MLI and the fall survey, snow crab survey, and Northumberland survey by the GFC. Several other surveys by MLI provided useful data, some even with a long time series but with limited geographical coverage (surveys for snow crab, scallop and surf clam), while others were conducted less frequently and at a small geographic scale (surveys for clam and whelk). Cod and Greenland halibut stomach contents have also been used as a sampling device for the distribution on some benthic invertebrates. Despite the large number of surveys considered here, the coastal zone (less than 50 m deep in the Estuary and the nGSL and less than 30 m deep in the sGSL) was not adequately sampled, except for the Northumberland Strait. In the main section of this document, distributions of 44 taxa are presented and have guided the identification of EBSAs : 4 general groups (soft corals, anemones, sponges, ascidians), 5 echinoderms, 6 molluscs, 1 mysid, 22 shrimps, and 6 crabs. Zones of maximum relative abundance of each taxa, weighted inversely to their surface area of high abundance, were used to calculate an index of benthic invertebrate concentration for each 10 x 10 km square sampled in the study area. This index was the primary tool in the identification of potential EBSAs. As a result, 17 EBSAs for benthic invertebrates are proposed. However, it is important to keep in mind that only a small proportion (approximately 0.02 %) of the benthic invertebrate species known to be present in the study area was considered in the process. In particular, the lack of data for the coastal zone is a major gap. We present in appendix to this report the data on 6 coastal species that we were able to obtain.

SAVENKOFF, C., D.P. SWAIN, J.M. HANSON, M. CASTONGUAY, M.O. HAMMILL, H. BOURDAGES, L. MORISSETTE, D. CHABOT, 2007. Effects of fishing and predation in a heavily exploited ecosystem : comparing periods before and after the collapse of groundfish in the southern Gulf of St. Lawrence (Canada). Ecol. Model., 204(1-2): 115-128 .

Mass-balance models, using inverse methodology, were applied to the southern Gulf of St. Lawrence for the mid-1980s and the mid-1990s to describe ecosystem structure, trophic group interactions, and the effects of fishing and predation on the ecosystem for periods preceding and following the collapse of groundfish stocks in this area. These models were used to determine how the ecosystem changed, and whether its structure and functioning were affected by the observed changes in key species between the two time periods. Our analyses indicate that the ecosystem structure shifted dramatically from one previously dominated by piscivorous groundfish and small-bodied forage species (e.g., capelin, herring, and shrimp) in similar proportions to one now dominated by small-bodied forage species. Overfishing removed a functional group, large-bodied demersal predators that has not been replaced 12 years after the cessation of heavy fishing, and left marine mammals such as seals and cetacea as top predators of many species (especially fishes) during the mid-1990s. Predation by marine mammals on fish increased from the mid-1980s to the mid-1990s while predation by large fish on fish decreased. A change in the prey of seals from juvenile cod to capelin occurred between the models for the mid-1980s and the mid-1990s consistent with observed shifts in the abundance of the two prey species between the two time periods. These major changes were accompanied by a decrease in total catches and a transition in landings from long-lived and piscivorous groundfish toward planktivorous pelagic fish and invertebrates. ©2007 Elsevier B.V.

GILBERT, D., D. CHABOT, P. ARCHAMBAULT, B. RONDEAU, S. HÉBERT, 2007. Appauvrissement en oxygène dans les eaux profondes du Saint-Laurent marin : causes possibles et impacts écologiques. Naturaliste can., 131(1): 67-75 .

[Abstract only available in French]
Depuis les années 1930, les concentrations d'oxygène ont baissé de moitié dans l'estuaire maritime du Saint-Laurent, à 300 m de profondeur. Un accroissement de la proportion d'eau chaude et pauvre en oxygène du GulfStream, au détriment de la proportion d'eau froide et bien oxygénée du courant du Labrador, expliquerait entre la moitié et les deux tiers de la baisse. Parmi les autres facteurs naturels et anthropiques susceptibles d'expliquer le reste de la baisse d'oxygène, les plus probables impliquent un flux accru de matières organiques des eaux de surface vers les fonds marins, où leur décomposition augmente la consommation d'oxygène. Nous montrons notamment une faible tendance à la hausse des nitrates à Lauzon, depuis 1990. Certaines espèces d'animaux marins comme le turbot, la crevette nordique et les polychètes Myriochele et Ampharete sont très abondantes dans les zones les plus pauvres en oxygène de l'estuaire et du golfe du Saint-Laurent, tandis que d'autres espèces comme la morue en sont absentes. Le seuil de tolérance aux faibles teneurs d'oxygène varie donc d'une espèce à l'autre. Nous devrons améliorer nos connaissances à cet égard afin de mieux comprendre les conséquences de l'appauvrissement en oxygène sur la biodiversité et le fonctionnement de l'écosystème.©2007 La Société Provancher d'histoire naturelle du Canada

SAVENKOFF, C., M. CASTONGUAY, D. CHABOT, M. O. HAMMILL, H. BOURDAGES, L. MORISSETTE, 2007. Changes in the northern Gulf of St. Lawrence ecosystem estimated by inverse modelling : evidence of a fishery-induced regime shift?. Estuar. Coast. Shelf Sci., 73(3-4): 711-724 .

Mass-balance models have been constructed using inverse methodology for the northern Gulf of St. Lawrence for the mid-1980s, the mid-1990s, and the early 2000s to describe ecosystem structure, trophic group interactions, and the effects of fishing and predation on the ecosystem for each time period. Our analyses indicate that the ecosystem structure shifted dramatically from one previously dominated by demersal (cod, redfish) and small-bodied forage (e.g., capelin, mackerel, herring, shrimp) species to one now dominated by small-bodied forage species. Overfishing removed a functional group in the late 1980s, large piscivorous fish (primarily cod and redfish), which has not recovered 14 years after the cessation of heavy fishing. This has left only marine mammals as top predators during the mid-1990s, and marine mammals and small Greenland halibut during the early 2000s. Predation by marine mammals on fish increased from the mid-1980s to the early 2000s while predation by large fish on fish decreased. Capelin and shrimp, the main prey in each period, showed an increase in biomass over the three periods. A switch in the main predators of capelin from cod to marine mammals occurred, while Greenland halibut progressively replaced cod as shrimp predators. Overfishing influenced community structure directly through preferential removal of larger-bodied fishes and indirectly through predation release because larger-bodied fishes exerted top-down control upon other community species or competed with other species for the same prey. Our modelling estimates showed that a change in predation structure or flows at the top of the trophic system led to changes in predation at all lower trophic levels in the northern Gulf of St. Lawrence. These changes represent a case of fishery-induced regime shift. ©2007 Elsevier Ltd.

CHABOT, D., R. MILLER, 2007. A rare case of completely ambicoloured Atlantic halibut, Hippoglossus hippoglossus, from the lower St. Lawrence estuary, Quebec. Can. Field-Nat., 121(1): 35-39 .

An Atlantic halibut (Hippoglossus hippoglossus) (41.4 cm fork length) with the same pigmentation on the blind side as on the ocular side (ambicoloration) was captured in the lower St. Lawrence estuary, Canada, on 24 June 2004. This specimen represents the most extreme case of ambicoloration published for this species to date. As in other cases of extreme ambicoloration, this specimen shows other signs of abridged metamorphosis and reduced asymmetry, such as incomplete migration of the left eye and a hooked dorsal fin. Studies of hatchery-reared larvae have shown that the most common cause of malpigmentation, including ambicoloration, in halibut is a diet containing inadequate amounts and proportions of essential unsaturated fatty acids shortly before metamorphosis. Even though not expected to be common in the wild, inadequate diet for a short duration before metamorphosis is the most likely cause of ambicolouration in wild halibut.©2007 The Ottawa Field-Naturalists'Club Transactions

DAOUD, D., D. CHABOT, C. AUDET, Y. LAMBERT, 2007. Temperature induced variation in oxygen consumption of juvenile and adult stages of the northern shrimp, Pandalus borealis. J. Exp. Mar. Biol. Ecol., 347(1-2): 30-40 .

The impact of temperature on oxygen consumption (MO2) of Pandalus borealis was measured in the laboratory for juvenile, male and female shrimp at 2, 5 and 8 °C, the temperature range where P. borealis is generally found in the Northwest Atlantic. Measurements of MO2 were taken every 60 min over 7-10 days on 0.22 to 13.80 g shrimp. These long-term measurement periods insured acclimation to the respirometers and allowed calculation of standard metabolic rate of individuals (SMRind). SMRind was linearly related to body mass (log transformed data) and the mass-exponent for the species was 0.56. The effects of wet body mass (Ww) and temperature (T) on SMRind were described by: SMRind = 10(0.57 log (Ww)+0.04 T-1.21), with SMRind expressed in mg O2 h-1, Ww in g and T in °C. This model explained 92 % of the variability in SMRind. Mass-specific MO2 adjusted for a 5 g shrimp (SMR5g) was not influenced by developmental stage indicating that the regression model for SMRind was valid regardless of variations in size at maturity and sex transition. Routine and active metabolic rates followed the same variation pattern in relation to temperature and developmental stage than SMR. Finally, thermal coefficients (Q10) were in the normal range found for crustaceans, Q10 values varying from 1.73 to 4.97. &2007 Elsevier B.V.

SAVENKOFF, C., M. CASTONGUAY, D. CHABOT, A. FRÉCHET, M.O. HAMMILL, L. MORISSETTE, 2006. Main prey and predators and estimates of mortality of Atlantic cod (Gadus morhua) in the northern Gulf of St. Lawrence during the mid-1980s, mid-1990s, and early 2000s. Can. Tech. Rep. Fish. Aquat. Sci., 2666, 32 p .

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We used results of mass-balance models to describe the changes in the structure and functioning of the northern Gulf of St. Lawrence ecosystem related to Atlantic cod (Gadus morhua) for the mid-1980s, the mid-1990s, and the early 2000s. The net decrease in biomass of the demersal species in the early 1990s and the ensuing drop in predation led to an ecosystem structure dominated by small-bodied pelagic species and marine mammals. Cod (both small and large) consumption largely decreased from the mid-1980s to the mid-1990s. Large zooplankton, shrimp (mainly Pandalus borealis), capelin (Mallotus villosus), and small planktivorous pelagics (mainly Atlantic herring Clupea harengus) were among the main prey consumed by small cod for each time period. The proportion of fish in the diet of large cod decreased from 77 % in the mid-1980s, when they mainly consumed capelin, to 49 % in the early 2000s. In the early 2000s, the main prey of large cod were large zooplankton and shrimp. There was a net decrease in total mortality and predation on small and large cod from the mid-1980s to the mid-1990s. Fishing mortality on large cod also decreased over the same time period (moratorium). From the mid- 1990s to the early 2000s, the biomass of both small and large cod doubled. Predation on small cod increased slightly over the same time period while predation on large cod was similar. However, the most noticeable increase in mortality on large cod from the mid-1990s to early 2000s came from fishing, which increased by a factor of 23. Cannibalism also appeared to be a non-negligible source of mortality on cod. A high proportion (between 30 and 40 %) of the total mortality of large cod could not be explained by either fishing or predation for each period (i.e., other mortality causes). This suggests that other processes in the ecosystem were not accounted for in the models

SAVENKOFF, C., B. MORIN, D. CHABOT, M. CASTONGUAY, 2006. Main prey and predators of redfish (Sebastes spp.) in the northern Gulf of St. Lawrence during the mid-1980s,mid-1990s, and early 2000s. Can. Tech. Rep. Fish. Aquat. Sci., 2648, 23 p .

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We used results of mass-balance models to describe the changes in the structure and functioning of the northern Gulf of St. Lawrence ecosystem related to redfish (Sebastes spp.) for the mid-1980s, the mid-1990s, and the early 2000s. The net decrease in biomass of the demersal species in the early 1990s and the ensuing drop in predation led to an ecosystem structure dominated by small-bodied pelagic species and marine mammals. Redfish consumption largely decreased from the mid-1980s to the early 2000s. Large zooplankton, capelin (Mallotus villosus), and small zooplankton were the main prey consumed by redfish for each time period. There was a net decrease in total mortality and predation on redfish from the mid-1980s to early 2000s. Fishing mortality also decreased over the same time period as the redfish fishery in the Gulf has been under moratorium since 1995. Predation was the main cause of redfish mortality for each time period. The main predators of redfish were large cod (Gadus morhua) during the mid-1980s and harp seals (Pagophilus groenlandicus) and skates during the mid-1990s and early 2000s. Even though the proportion of redfish in the diet composition of each of these three predators was generally low, their predation could account for high percentages of total mortality on redfish. Cannibalism also appeared to be an important source of redfish mortality (between 10 and 15 % of total mortality)

SAVENKOFF, C., F. GRÉGOIRE, M. CASTONGUAY, J.M. HANSON, D. CHABOT, D.P. SWAIN, 2006. Main prey and predators of Atlantic herring (Clupea harengus L.) in the Gulf of St. Lawrence during the mid-1980s, mid-1990s, and early 2000s. Can. Tech. Rep. Fish. Aquat. Sci., 2643, 28 p .

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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 herring populations (Clupea harengus L.) for the mid-1980s, the mid-1990s, and the early 2000s. Small and large zooplankton were the main prey of herring for each ecosystem and each time period. Herring was among the three main prey in both ecosystems for each time period. Predation was the main cause of herring mortality in the northern Gulf for all time periods and in the southern Gulf during the mid-1980s. Large cod (Gadus morhua) and redfish (Sebastes spp.) were progressively replaced by cetacea and seals as main herring predators from the mid-1980s to early 2000s in the northern Gulf. In the southern Gulf, large cod and harp seals were the main predators during the mid-1980s while predation and fishing mortality were of similar importance during the mid-1990s. Fishing was among the three main mortality causes in absolute terms in the northern and southern Gulf in each time period. Fishing effects on forage species since the early 1990s seem to counter the expected increases in biomass of these species following the net decrease in biomass of the demersal species and the ensuing drop in predation.

SAVENKOFF, C., L. SAVARD, B. MORIN, D. CHABOT, 2006. Main prey and predators of northern shrimp (Pandalus borealis) in the northern Gulf of St. Lawrence during the mid-1980s, mid-1990s, and early 2000s. Can. Tech. Rep. Fish. Aquat. Sci., 2639, 28 p .

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We used results of mass-balance models to describe the changes in the structure and functioning of the northern Gulf of St. Lawrence ecosystem related to northern shrimp (Pandalus borealis) for the mid-1980s, the mid-1990s, and the early 2000s. The net decrease in biomass of the large-bodied demersal species and the ensuing drop in predation in the mid-1990s may explain the increase in abundance of the northern shrimp at the end of the 1990s. Shrimp was among the main prey species, and predation was the main cause of shrimp mortality for all time periods. Greenland halibut (Reinhardtius hippoglossoides) progressively replaced cod (Gadus morhua) and redfish (Sebastes spp.) as the main shrimp predators. Since the biomass of Greenland halibut sharply increased since 1995, its effect via predation as well as fishing pressure should be considered in the elaboration of management strategies for shrimp in the northern Gulf of St. Lawrence.

GRÉGOIRE, F., C. SAVENKOFF, D. CHABOT, 2006. Pêche, biologie, régime alimentaire et prédation du maquereau bleu (Scomber scombrus L.) dans les sous-régions 3 et 4 de l'OPANO en 2005 ; Atlantic mackerel (Scomber scombrus L.) fishery, biology, diet composition and predation in NAFO Subareas 3 and 4 in 2005. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2006/095, 84 p .

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In 2005, landings of Atlantic mackerel (Scomber scombrus L.) in the northwest Atlantic totalled 93,512 t, which represents a decrease of 14,020 t from 2004. In eastern Canada, 51,918 t were landed, including 40,724 t in Newfoundland only. Most of the landings of the west coast of Newfoundland were from unit areas 4Rb, 4Rc and 4Rd with 4,576 t, 1,334 t, and 7,614 t. On the east coast of Newfoundland, the most important landings were from unit areas 3Kd, 3Kh, 3Ki, 3Lb, and 3Lf with 8,570 t, 10,647 t, 3,380 t, 1,856 t, and 1,552 t, respectively. Mackerel catches of this importance are unusual for the east coast of Newfoundland. The other important unit areas were 4Tg and 4Tl in the southwestern Gulf of St. Lawrence with landings of 944 t and 625 t, respectively, and unit areas 4Xm and 4Xo, in Nova Scotia, with 3,513 t and 3 577 t. Since 2000, the most striking feature of the commercial mackerel fishery has been the presence of a high abundance and very large proportion of fish from the 1999 year-class. Over the past six years, this year-class has accounted for between 30% and 77% of the total number of fish caught, which hasn’t been seen since the late 1960s. In 2005, this year-class was dominant during the second and fourth quarter compared to the 2004 and 2003 year-classes for the third quarter. The analyses of the biological data indicate that the proportion of mature fish at age has decreased in recent years. The size at which 50% of the fish were mature, or L50, was 254.9 mm in 2005. Since 1999, the annual L50 values have been below or slightly above the minimum legal catch size of 250 mm. Data collected in the mid-1980s showed that mackerel in the Northern Gulf of St. Lawrence (Divisions 4RS) fed mainly on small (< 5 mm) and large (= 5 mm) zooplankton. During the mid-1990s and the beginning of the 2000s, the importance of the small and large zooplankton in the diet slightly decreased and was replaced by shrimp (Pandalus borealis) and capelin (Mallotus villosus). As shown by the results of different models 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. Cetaceans were still the main predators of mackerel in the mid-1990s and the beginning of 2000s. The same models showed that fishery related mortalities gradually increased from 2% in the mid-1980s to 15% in the mid-1990s, and finally to 30% of total mortality in the early 2000s. The main sources of uncertainty related to the present assessment are the unrecorded catches and the contribution of mackerel from Canadian waters in the American catches from the Gulf of Maine and Georges Bank areas. Because of this imprecision, of the recent increase of fishing effort and of the uncertainty regarding the results from the recent abundance surveys, the current TAC level of 75,000 t could be lowered over the next year

LAFRANCE, P., M. CASTONGUAY, D. CHABOT, C. AUDET, 2005. Ontogenetic changes in temperature preference of Atlantic cod. J. Fish Biol., 66(2): 553-567 .

Final thermal preferendum (T) experiments were conducted in a horizontal thermal gradient tank from the beginning of August 2001 to mid-November 2001 using Atlantic cod Gadus morhua from 6.5 to 79.0 cm fork length (LF). The value of T varied significantly (P <0.005) with LF (T= 7.23-0.054LF), with smaller (younger) fish choosing higher temperatures than larger (older) fish. The preferendum varied from 6.9 °C for fish of 6.5 cm to 3.0 °C for those of 79.0 cm. Experiments comparing fish positions in the gradient tank between thermal gradients of 0.5-11.0 and 4.5-14.5 °C demonstrated that fish positions were determined by temperature selection instead of undesirable tank effects. This study is the first to demonstrate the effect of ontogeny on temperature preferences of a marine fish species.©2005 Minister of Public Works and Government Services Canada

OUELLET, P., D. CHABOT, 2005. Rearing Pandalus borealis (Krøyer) larvae in the laboratory : I. Development and growth at three temperatures. Mar. Biol., 147(4): 869-880 .

Northern shrimp Pandalus borealis (Krøyer) larvae hatch in the northern Gulf of St. Lawrence from early May to the end of June, and larval development occurs over a range of relatively cold water temperatures. Because of the long duration of the pelagic phase and the difficulty of sampling all successive larval stages at sea, we used laboratory experiments to assess the effects of water temperature on larval development and growth. In spring 2000, P. borealis larvae were reared from hatching to the first juvenile stages (i.e., stage VI and VII) at three temperatures (3, 5, and 8 °C) representing conditions similar to those in spring in the northern Gulf of St. Lawrence. Larval development and growth were dependent on temperature, with longer duration and smaller size (cephalothorax length, CL , and dry mass, DM) at 3 °C relative to the 5 and 8 °C treatments. There were no significant differences in the morphological characters of the different stages among treatments, indicating that regular moults occurred at each temperature. The results suggest a negative impact of cold temperatures (lower intra-moult growth rates and smaller size) and, possibly, higher cumulative mortality due to longer development time that could affect the success of cohorts at sea. However, CL and DM for stage III and later larvae were smaller than those of larvae identified at the same developmental stage in field locations. It is possible that the diet offered to larvae in this experiment (Artemia nauplii, either newly hatched nauplii or live adults, depending on the developmental stage) was not optimal for growth, even though it is known to support successful P. borealis larval development. In the field, there is the possibility that phytoplankton contributes to the larval diet during the first stages and stimulates development of the digestive glands. Furthermore, the nutritional quality of the natural plankton diet (e.g., high protein content, fatty acid composition) might be superior and favourable to higher growth rates even at lower temperatures.©2005 Springer-Verlag

SAVENKOFF, C., M. CASTONGUAY, D. CHABOT, 2005. Effets de la pêche et la prédation sur l'écosystème du nord du golfe du Saint-Laurent: changements depuis le milieu des années 1980 jusqu'au milieu des années 1990. Naturaliste can., 129(1): 103-109 .

[Abstract only available in French]
En développant des modèles écosystémiques, le programme CDEENA qui vient de prendre fin, a cherché à expliquer les changements survenus dans le golfe depuis le milieu des années 1980 jusqu'au milieu des années 1990, et notamment leur impact sur la morue. Les résultats montrent notamment le rôle déterminant de la surpêche, l'importance de la prédation par les phoques mais aussi le changement des conditions environnementales.

SAVENKOFF, C., M. CASTONGUAY, R. METHOT, D. CHABOT, M.O. HAMMILL, 2005. Input data and parameter estimates for ecosystem models of the northern Gulf of St. Lawrence (2000-2002). Can. Tech. Rep. Fish. Aquat. Sci., 2588, 96 p .

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Mass-balance models were used to reconstruct trophic flows through the whole northern Gulf of St. Lawrence ecosystem (NAFO divisions 4Rs) for the 2000-2002 period. The whole-system model of the northern Gulf of St. Lawrence is divided into 31 functional groups or compartments from phytoplankton and detritus to marine mammals and seabirds, including harvested species of pelagic, demersal, and benthic domains. We present here details of the input data (biomass, production, consumption, export, and diet composition) for each compartment used for modelling. The parameter estimates from inverse modelling are also shown for comparisons. The successful development of ecosystem models will provide powerful new tools to evaluate the impact of human and environmental factors on marine ecosystems

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 .

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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)

CHABOT, D., P. OUELLET, 2005. Rearing Pandalus borealis larvae in the laboratory. II. Routine oxygen consumption, maximum oxygen consumption and metabolic scope at three temperatures. Mar. Biol., 147(4): 881-894 .

Larvae of the northern shrimp Pandalus borealis (Krøyer) are pelagic. In the Estuary and Gulf of St. Lawrence, Canada, the early stages are found in the upper 25-m of the water column in spring and early summer and are expected to experience a range of water temperatures from as low as 0 °C to as high at 6 °C. Little is known of the impact of water temperature on metabolic requirements of northern shrimp larvae. In this study, routine respiration (VO2), maximum respiration (electron transport system activity, ETSA) and metabolic scope for growth (MS, ETSA-VO2) of northern shrimp larvae were measured as a function of temperature (3, 5 and 8 °C), developmental stage (I-V at 3 °C, I-VII at 5 °C and 8 °C) and growth rate in dry mass. After logarithmic transformation, all three metabolic variables were linearly related to dry mass. The increase in VO2 with body mass was faster at 5 °C than at 3 or 8 °C, whereas with ETSA this increase was slower. As a result, MS increased more slowly with dry mass at 5 °C than at 3 and 8 °C. However, MS did not limit growth in this study, since it explained only 39 % of the variability in growth. All three metabolic variables as well as growth varied together as a function of temperature and ontogeny. Q10 of all three metabolic variables ranged from 1.6 and 2.2 for stages I-V larvae, except for VO2 at stage I (3.9) and stage III (2.9).©2005 Springer-Verlag

FRÉCHET, A., J. GAUTHIER, P. SCHWAB, L. PAGEAU, C. SAVENKOFF, M. CASTONGUAY, D. CHABOT, C. TOURNOIS, J.-F. LUSSIER, J. SPINGLE, F. COLLIER, 2005. L’état du stock de morue du nord du golfe du Saint-Laurent (3Pn, 4RS) en 2004 ; The status of cod in the Northern Gulf of St. Lawrence (3Pn, 4RS) in 2004. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2005/060, 72 p .

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The commercial landings for the Northern Gulf of St. Lawrence (3Pn, 4RS) have reached a maximum of 106,000 tons while the spawning biomass has reached a maximum of 378,000 tons in 1983. Afterwards, the stock was reduced to a minimum mature biomass of 9,000 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 26,000 tons at the reopening of the commercial fishery in 1997. Since 1997, the commercial fishery has been conducted by fixed gears only (longlines, gillnets and handlines). Despite the low fishing effort and a second moratorium in 2003, the mature biomass remains low at 38,000 tons in 2005

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 .

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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.

SAINTE-MARIE, B., R. DUFOUR, L. BOURASSA, D. CHABOT, M. DIONNE, D. GILBERT, A. RONDEAU, J.-M. SÉVIGNY, 2005. Critères et proposition pour une définition des unités de production du crabe des neiges (Chionoecetes opilio) dans l'estuaire et le nord du golfe du Saint-Laurent ; Criteria and proposition for the definition of snow crab (Chionoecetes opilio) production units in the estuary and northern Gulf of St. Lawrence. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2005/059, 20 p .

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The current borders of snow crab management areas in the Department of Fisheries and Oceans (DFO) Québec region are not based on biological or oceanographical criteria and some times enclose territories with very different characteristics. As noted by the FRCC (2005), there is a need to define biological production units to better monitor the status and ensure conservation of populations. Toward that goal, we conducted a literature review and used trawl data from the Gulf of Saint Lawrence to identify the biological and physical factors that constrain the distribution and dispersal of snow crab. This information allows us to characterize snow crab habitat, which can be defined as a territory with bottoms of soft sediments, bathed by waters with a salinity > 26 ‰, part of which is at a temperature of 0-2 °C and the remainder at a temperature varying from about -1.5 to 4 °C. The surface waters above this territory must generally have a salinity > 26 ‰ and warm up to 5-15 °C for several weeks for larvae to survive and grow. Snow crab larvae can disperse themselves over long distances and this may explain the weak genetic differentiation of populations within the Gulf. However, the various benthic stages generally have a much smaller dispersal capability. We describe the criteria used to define biological production units and on that basis we propose to divide the territory under the responsibility of DFO-Québec into seven units.

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 .

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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. 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 .

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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.

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 .

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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.

SAVENKOFF, C., H. BOURDAGES, M. CASTONGUAY, L. MORISSETTE, D. CHABOT, M. HAMMILL, 2004. Input data and parameter estimates for ecosystem models of the northern Gulf of St. Lawrence (mid-1990s). Can. Tech. Rep. Fish. Aquat. Sci., 2531, 93 p .

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In the present study, we use Ecopath and inverse methods to reconstruct trophic flows through the whole northern Gulf of St. Lawrence ecosystem (NAFO zones 4RS) for the mid-1990s period, prior to the groundfish stock collapse. This was a period of relatively constant biomass for the major species. The whole-system model of the northern Gulf of St. Lawrence is divided into 32 functional groups or compartments from phytoplankton and detritus to marine mammals and seabirds, including harvested species of pelagic, demersal, and benthic domains. We present here details of the input data (biomass, production, consumption, export, and diet composition) for each compartment used for modelling. the successful development of ecosystem models proposed by the Comparative Dynamics of Exploited Ecosystems in the Northwest Atlantic (CDEENA) program will provide powerful new tools to evaluate the impact of human and environmental factors on a variety of Atlantic shelf ecosystems.

SAVENKOFF, C., M. CASTONGUAY, A.F. VÉZINA, S.-P. DESPATIE, D. CHABOT, L. MORISSETTE, M.O. HAMMILL, 2004. Inverse modelling of trophic flows through an entire ecosystem: the northern Gulf of St. Lawrence in the mid-1980s. Can. J. Fish. Aquat. Sci., 61: 2194-2214 .

Mass-balance models using inverse methodology have been constructed for the northern Gulf of St. Lawrence ecosystem in the mid-1980s, before the groundfish collapse. The results highlight the effects of the major mortality sources (fishing, predation, and other sources of mortality) on the fish and invertebrate communities. Main predators of fish were large cod (Gadus morhua followed by redfish (Sebastesspp.), capelin (Mallotus villosus), and fisheries. Large cod were the most important predator of small cod, with cannibalism accounting for at least 44 % of the mortality of small cod. The main predators of large cod were harp (Phoca groenlandica) and grey (Halichoerus grypus) seals. However, predation represented only 2 % of total mortality on large cod. Mortality other than predation dominated the mortality processes at 52 % of the total, while the fishery represented 46 %. Tests were performed to identify possible sources of this unexplained mortality. The only way to significantly reduce unexplained mortality on large cod in the model was to increase landings of large cod above those reported. This suggests that fishing mortality was substantially underestimated in the mid-1980s, just before the demise of a cod stock that historically was the second largest in the northwest Atlantic.©2004 NRC Canada

DUTIL, J.-D., J. GAUTHIER, A. FRÉCHET, D. CHABOT, 2003. Cod stocks rebuilding and fish bioenergetics: low productivity hypothesis ; Le rétablissement des stocks de morue et la bio-énergique des poissons: l'hypothèse d'une faible productivité. DFO, Canadian Science Advisory Secretariat, Research Document ; DFO, Canadian Science Advisory Secretariat, Research Document, 2003/060, 39 p .

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The lack of response of several cod stocks and other species to management regulations expected to promote stock rebuilding is hypothesized to stem from a combined (multiplicative) effect of 3 factors : 1. natural intrinsic productivity is low; 2. natural intrinsic productivity has declined; 3. pressures on production associated with natural and fishing mortality have remained high or have increased relative to these stocks/species rates of production. Annual production per capita and per unit biomass varies among stocks, with northerly distributed stocks or stocks inhabiting cold and sometimes hypoxic environments being notably less productive than other stocks. Cod in less productive stocks grow slowly, recruit at an older age, become sexually mature at a later age and a smaller size and produce fewer eggs. Fish condition is on average lower and varies much more in these stocks compared to other stocks. Environmental conditions have changed progressively after the mid ‘80s with conditions during the moratorium not favorable to cod production in northern areas of the western North Atlantic. Fish stocks in these areas have thus become less productive and hence less resilient, i.e., less able to resist and respond to perturbations, whether man-made or environmental. There are several recent indications that individual performance has improved, but fishing pressure has not been relaxed sufficiently to offset increased predation pressures and low productivity associated with limiting environmental conditions. These stocks are unable to produce new biomass fast and as a result stock rebuilding is expected to take much longer than would be predicted for other stocks living in more favorable environments, particularly if exploited under enduring adverse environmental conditions. Strengths and weaknesses of this hypothesis are discussed.

MORISSETTE, L., S.-P. DESPATIE, C. SAVENKOFF, M.O. HAMMIL, H. BOURDAGES, D. CHABOT, 2003. Data gathering and input parameters to construct ecosystem models for the nothern Gulf of St. Lawrence (mid-1980s). Can. Tech. Rep. Fish. Aquat. Sci., 2497, 94 p .

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In the present study, we use Ecopath and inverse methods to reconstruct trophic flows through the whole northern Gulf of St. Lawrence ecosystem (NAFO zones 4RS) for the middle 1980s period, prior to the groundfish stock collapses. This was a period of relatively constant biomass for the major species. The whole-system model of the northern Gulf of St. Lawrence is divided into 32 functional groups or compartments from phytoplankton and detritus to marine mammals and seabirds, including harvested species of pelagic, demersal, and benthic domains. We present here details of the input data (biomass, production, consumption, export and diet composition) for each compartment used for modelling. The successful development of Northwest Atlantic (CDEENA) program will provide powerful new tools to evaluate the impact of human and environmental factors on a variety of Atlantic shelf ecosystems.

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 .

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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.

DUTIL, J.-D., Y. LAMBERT, D. CHABOT, 2003. Winter and spring changes in condition factor and energy reserves of wild cod compared with changes observed during food-deprivation in the laboratory. ICES J. Mar. Sci., 60: 780-786 .

DARBYSON, E., D.P. SWAIN, D. CHABOT, M. CASTONGUAY, 2003. Diel variation in feeding rate and prey composition of herring and mackerel in the southern Gulf of St. Lawrence. J. Fish Biol., 63: 1235-1257 .

DUTIL, J.-D., D. CHABOT, 2002. Impact of hypoxia on Atlantic cod in the northern Gulf of St. Lawrence. Pages 51-60 in R.V. Thurston (ed.). Fish Physiology, Toxicology and Water Quality : proceedings of the Sixth International Symposium, La Paz, B.C.S. Mexico, January 22-26, 2001 .

Oxygen levels range from 70 to 30 % saturation or less in waters deeper than 175 m in the Gulf of St. Lawrence. The potential impact of hypoxia on two stocks of Atlantic Cod (Gadus morhua) that live in the Gulf of St. Lawrence was investigated. In a first experiment (84 days, three meals per week), cod were raised under six oxygen treatments between 45 and 93 % saturation. Growth and food ingestion were limited by oxygen below 70 % saturation. In a second experiment (56 days), we varied meal frequency (one, three, and seven meals per week) for cod held at two regimes of dissolved oxygen (40 and 90 % saturation). In normoxia, growth was significantly reduced at one meal per week compared to three and seven meals per week. In hypoxia, however, there was no difference in growth between the three feeding frequencies. At one meal per week, growth was equally poor at both oxygen levels. At three and seven meals per week, growth was faster in normoxia than in hypoxia, although this was significant only at the highest feeding frequency. In both experiments, food consumption explained practically all of the variability in growth rate.Crown©2002

STARR, M., M. HARVEY, P.S. GALBRAITH, D. GILBERT, D. CHABOT, J.-C. THERRIAULT, 2002. Recent intrusion of Labrador Shelf waters into the Gulf of St. Lawrence and its influence on the plankton community and higher trophic levels. ICES C.M., 2002/N:16, 10 p .

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SAINTE-MARIE, B., D. CHABOT, 2002. Ontogenetic shifts in natural diet during benthic stages of American lobster (Homarus americanus), off the Magdalen Islands. Fish. Bull., 100: 106-116 .

CHABOT, D., G.B. STENSON, 2002. Growth and seasonal fluctuations in size and condition of male Northwest Atlantic harp seals Phoca groenlandica : an analysis using sequential growth curves. Mar. Ecol. Prog. Ser., 227: 25-42 .

DESPATIE, S.-P., M. CASTONGUAY, D. CHABOT, C. AUDET, 2001. Final thermal preferendum of Atlantic cod : effect of food ration. Trans. Am. Fish. Soc., 130: 263-275 .

CHABOT, D., J.-D. DUTIL, C. COUTURIER, 2001. Impact of chronic hypoxia on food ingestion, growth and condition of Atlantic cod, Gadus morhua. ICES C.M., 2001/V:05, 17 p .

LE FRANÇOIS, N.R., J.-D. DUTIL, P. BLIER, K. LORD, D. CHABOT, 2001. Tolerance and growth of juvenile common wolffish (Anarhichas lupus) under low salinity and hypoxic conditions: preliminary results. AAC Spec. Publ., 4: 57-59 .

Juvenile wolffish salinity and hypoxia tolerance were investigated at constant water temperature (10 °C). Twenty fish (mean weight 0.11g) were transferred directly to 0 (FW), 7, 14, 21, 28 and 35 ppt water in a closed-circulation system to assess salinity tolerance. No fish survived more than 6h in FW, however, mortality was negligible at 0-0.05 % for the other groups. A second challenge test using O.408-g fish, was conducted for 72 h at 0 to 7 and 28 ppt. Cumulative mortality was 100 % in FW and was down to 33 % at 6 ppt after 72 h. No mortalities occurred between 7 and 28 ppt. A 2O-day growth trial was performed using the survivors from the first challenge test (7, 14, 21, 28, and 35 ppt). This indicated no detrimental growth effect at salinities as low as 7 ppt. Protein content and total length were significantly higher at lower salinities. The impact of low oxygen tension on the survival of 1 +juveniles (average weight - 40 g) was also examined (LC50 96 hours; 16, 22, 28, 34, 40 and 100 % oxygen saturation). No fish survived at 16 % saturation; however, no mortality occurred beyond 22 %. The impact of low oxygen tension on growth performance is underfurther investigation.©2001 Aquaculture Association of Canada

CHABOT, D., G.B. STENSON, 2000. Implantation date, grownth rate, and allometric relationships in foetal Northwest Atlantic harp seals (Phoca groenlandica). Can. J. Zool., 78: 501-505 .

Using a sample of 150 female and 141 male fœtal Northwest Atlantic harp seals (Phoca groenlandica) collected between October and February of 1980-1995, we determined that the allometric relationship between total body mass and standard length did not differ between sexes and did not differ from the relationship calculated for fœtal harp seals from the study of Stewart and co-workers (R.E.A. Stewart, B.E. Stewart, D.M. Lavigne, and G.W. Miller 1991. Can. J. Zool. 67:2147-2157). Combining the data for foetuses from both studies, the exponent of the mass-length relationship was 2.75, significantly different from 3. Except for very small foetuses (<20 cm) standard length and mass1/2.75 increased linearly as gestation progressed. Equations are provided to estimate standard length and total mass of foetuses in the period August-February and to estimate sculp mass, core mass, and axillary girth from length for the period October-February. The most reliable estimate of implantation date (day 223, 11 August) was obtained by regressing sampling date1/2 on mass1/2.75©2000 National Research Council Canada

CHABOT, D., J.-D. DUTIL, 2000. Reduced growth of Atlantic Cod (Gadus morhua) in chronic hypoxia : the effect of varying meal frequency. Pages 75-79 in D. Val & D. MacKinlay. Fish surviving in extreme conditions : symposium proceedings : International Congress on the Biology of Fish, University of Aberdeen, Scotland, July 23-27, 2000 .

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DUTIL, J.-D., Y. LAMBERT, D. CHABOT, 2000. Estimating natural mortality of wild cod from controlled feeding and starvation experiments conducted in the laboratory. ICES C.M., 2000/R:01, 16 p .

The contribution of individual factors to the rate of natural mortality is usually unknown because it can hardly be measured in the wild, particularly in large ecosystems. Atlantic cod experienced a decline of their nutritional condition in the early 1990s in the Gulf of St. Lawrence. Whether or not natural mortality increased as a result of that decline was determined from controlled experiments conducted in the laboratory. The maximum range of several variables reflecting the nutritional condition of fed and unfed cod >30 cm was determined. By comparing values observed in the wild and in the laboratory, we concluded that wild cod may die of inanition during the spring period. The decline in the nutritional condition of wild cod from January to April was slower however than in cod deprived of food during a similar period of time in laboratory experiments. This indicates that cod fed but did not meet their energy requirements in winter prior to spawning. In contrast, the decline in condition from April to May matched the rate observed in the laboratory experiments, indicating that wild cod probably fast at this time. Estimates of survival probability based on the frequency distribution of condition factor during the spawning period appear to be unbiased as the rate of energy mobilization observed in the field never exceeded the rate observed in the laboratory.©2000 ICES

CHABOT, D., J.-D. DUTIL, 1999. Reduced growth of Atlantic cod in non-lethal hypoxic conditions. J. Fish Biol., 55: 472-491 .

CHABOT, D., J.-D. DUTIL, S. PLANTE, 1998. Survival and growth of Atlantic cod in hypoxia. Pages 39-44 in C. Kennedy & D. MacKinlay (ed.). Fish response to toxic environments : symposium proceedings. Physiology Section, American Fisheries Society .

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DUTIL, J.-D., M. CASTONGUAY, M.O. HAMMILL, P. OUELLET, Y. LAMBERT, D. CHABOT, H. BROWMAN, D. GILBERT, A. FRÉCHET, J.-A. GAGNÉ, D. GASCON, L. SAVARD, 1998. Environmental influences on the productivity of cod stocks : some evidence for the northern Gulf of St. Lawrence, and required changes in management practices. DFO, Canadian Stock Assessment Secretariat, Research Document, 98/18, 42 p .

PLANTE, S., D. CHABOT, J.-D. DUTIL, 1998. Hypoxia tolerance in Atlantic cod. J. Fish Biol., 53: 1342-1356 .

CHABOT, D., P. GAGNON, E.A. DIXON, 1996. Effect of predator odors on heart rate and metabolic rate of wapiti. J. Chem. Ecol., 22: 839-868 .

CHABOT, D., G.B. STENSON, N.G. CADIGAN, 1996. Short- and long-term fluctuations in the size and condition of harp seal (Phoca groenlandica) in the Northwest Atlantic. NAFO Sci. Counc. Stud., 26: 15-32 .

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CHABOT, D., G.B. STENSON, N.B. CADIGAN, 1995. Short- and long-term fluctuations in the size and condition of harp seal (Phoca groenlandica) in the Northwest Atlantic. NAFO SCR Doc., 95/42, 27 p .

MORIN, B., B. BERNIER, D. CHABOT, J.J. MAGUIRE, 1995. Évaluation et biologie du flétan du Groenland (Reinhardtius hippoglossoides) du golfe du Saint-Laurent (4RST) en 1994. MPO, Pêches de l'Atlantique, Document de recherche, 95/59, 47 p .

Since 1992, Greenland halibut of Divisions 4RST is managed as a distinct population on the basis of yield per recruit. The main concentrations of Greenland halibut in the Gulf of St. Lawrence during the summer are found on the west side of Anticosti Island and to a lesser extent north of this Island and in the Esquiman Channel near the west coast of Newfoundland. Preliminary results on sexual maturity of Greenland halibut in the estuary of the St. Lawrence River had showed that the length where 50 % of the male and the female were mature were 39 and 56 cm respectively in 1993-94. Landings of 4RST Greenland halibut have increased from 2,800 t to 3,600 t between 1993 and 1994. Gillnet is the main fishing gear used in this fishery since the middle of the 1970's. The size of fish caught by gillnet in 1994 was mainly between 41-45 cm and 70 % of these fishes were female. Thus, the majority of the catch were immature fish. Abundance indices showed that the biomass of Greenland halibut is low but relatively stable since 1990. Exploitation rate is probably high and the low number of large fish results in the concentration of this exploitation on the annual recruitment. Thus, it is important to protect juveniles in order to allow the spawning biomass to increase.

FRÉCHET, A., P. SCHWAB, Y. LAMBERT, D. CHABOT, D. DECKER, G. ROWE, P. NADEAU, F. COLLIER, 1995. Les pêches sentinelles du stock de morue du nord du golfe du Saint-Laurent (3Pn, 4RS) en 1994 ; The sentinel fisheries of the northern Gulf of St. Lawrence cod stock (3Pn, 4RS) in 1994. MPO, Pêches de l'Atlantique, Document de recherche ; DFO, Atlantic Fisheries, Research Document, 95/54, 30 p .

The sentinel fisheries have been put in place for the first time in the fall of 1994. The main objective of these projects was to put a limited number of fishermen back in a fishing situation in order to have a follow up of the cod population while the commercial fishery is closed. Some 76 fishermen have done 185 fishing trips using fixed gear and 5 otter trawlers have conducted a stratified random groundfish survey in 4R and 3Pn. The catch rates of the fixed gear varied geographically, very low catch rates were observed along the Quebec Lower North-Shore and on the west coast of Newfoundland from the strait of Belle-Isle to the Port au Port peninsula. Good catch rates were observed in the southern part of 4R and 3Pn. These catch rates reflect the migratory behaviour of cod during that period. The estimation of the minimum trawlable biomass for cod from 4R and 3Pn from the December survey involving 5 otter-trawlers is 14,000 t. This value is very close to the biomass estimates derived during the January 1994 and August-September 1994 groundfish surveys conducted aboard the Gadus Atlantica and Alfred Needler respectively. The sentinel fisheries have also provided precious information on the condition of the seals caught accidently. Cod specimens were brought back for laboratory studies on feeding and condition (the relationship between the length and the weight of the fish). The diet was dominated with invertebrates whereas the diet during that period is generally dominated by fish. Samples from other sentinel fisheries should place these results into perspective. Finaly the condition of the cod have increased substantially compared with other samples collected previously on groundfish surveys conducted in January. The sentinel fisheries can thus be used in the follow up of populations of cod while under a moratorium and thus allow the fishermen to involve themselves directly in the stock assessment process.

CHABOT, D., 1994. Relationship between mass and body length in Australian fur seals. Mar. Mamm. Sci., 10: 250-251 .