Archived Content

Information identified as archived is provided for reference, research or recordkeeping purposes. It is not subject to the Government of Canada Web Standards and has not been altered or updated since it was archived. Please contact us to request a format other than those available.

Bibliography of the Maurice Lamontagne Institute

Martin CASTONGUAY

TAMDRARI, H., M. CASTONGUAY, J.-C. BRÊTHES, P.S. GALBRAITH, D.E. DUPLISEA, 2012. The dispersal pattern and behaviour of Atlantic Cod (Gadus morhua) in the northern Gulf of St. Lawrence : results from tagging experiments. Can. J. Fish. Aquat. Sci., 69(1): 112-121 .

We examined how the distribution of Atlantic cod (Gadus morhua) is influenced by abiotic (temperature, salinity, depth, suitable habitat) and biotic (stock biomass) factors based on tagging–recapture data collected from 1995 to 2008 by the Department of Fisheries and Oceans Canada in the northern Gulf of St. Lawrence. We calculated a centre of gravity index and a dispersion index using only individuals recaptured more than 1 year after tagging during the summer. The centre of gravity showed a northward expansion and eastward contraction in recent years, reflecting both fish distribution and changes in fishing effort. The dispersion index was significantly related to temperature, habitat suitability, and biomass but not to salinity or depth. These results indicate that interannual fluctuations of temperature and stock abundance both influence the dispersion pattern of cod. This new information could influence spatio-temporal fisheries management strategies for northern Gulf cod.©2012 NRC Research Press

BUI, A.O.V., M. CASTONGUAY, P. OUELLET, 2012. Distribution et abondance des larves et juvéniles de poissons dans l’estuaire maritime du St-Laurent : connectivité entre le Golfe, l’Estuaire et le Fjord du Saguenay ; Distribution and abundance of larval and juvenile fish in the lower St. Lawrence Estuary : connectivity among the Gulf, the Estuary, and the Saguenay Fjord. Rapp. tech. can. sci. halieut. aquat. ; Can. Tech. Rep. Fish. Aquat. Sci., 2981, 57 p .

Click to see all the text

This study greatly improved knowledge of the distribution and abundance of ichthyoplankton communities and of oneand two-year-old juveniles of demersal species in the Lower St. Lawrence Estuary. Data analysis revealed that the ichthyoplankton community in the Lower Estuary consisted mainly of non-commercial demersal species, while the species targeted in the Saguenay Fjord ice fishing (mainly redfish, Atlantic cod, and Greenland halibut or turbot) were present in the Lower Estuary at the juvenile stage. This suggests connectivity for these species among the Gulf of St. Lawrence, the Lower Estuary, and the Saguenay Fjord. Our results support the hypothesis that recruitment of redfish, cod, and Greenland halibut in the Saguenay Fjord is based on the immigration of juvenile fish from the Estuary.

CASTONGUAY, M., S. DUBÉ, 2011. Processus consultatif scientifique régional sur l'évaluation du stock de capelan du golfe du Saint-Laurent (4RST), 17 février 2011, Institut Maurice-Lamontagne ; Regional Science Advisory Process on the Assessment of the Gulf of St. Lawrence (4RST) Capelin Stock, February 17, 2011, Maurice Lamontagne Institute. MPO, Secrétariat canadien de consultation scientifique, Série des comptes rendus; DFO, Canadian Science Advisory Secretariat, Proceedings Series, 2011/016, 20 p .

Click to see all the text

CASTONGUAY, M., S. DUBÉ, 2011. Atelier régional sur la révision des poids, à l’âge en début d’année, de la morue utilisés dans le calcul de la biomasse du stock reproducteur (BSR), 15 octobre 2010, Institut Maurice-Lamontagne, Mont-Joli, Québec ; Regional Workshop on Review of the Beginning of the Year Weight-at-Age of Cod Used in Calculating the Spawning Stock Biomass (SSB), October 15, 2010, Maurice Lamontagne Institute, Mont-Joli, Quebec. MPO, Secrétariat canadien de consultation scientifique, Série des comptes rendus; DFO, Canadian Science Advisory Secretariat, Proceedings Series, 2011/006, 11 p .

Click to see all the text

ALS, T.D., M.M. HANSEN, G.E. MAES, M. CASTONGUAY, L. RIEMANN, K. AARESTRUP, P. MUNK, H. SPARHOLT, R. HANEL, L. BERNATCHEZ, 2011. All roads lead to home : Panmixia of European eel in the Sargasso Sea. Mol. Ecol., 20(7): 1333-1346 .

European eels (Anguilla anguilla) spawn in the remote Sargasso Sea in partial sympatry with American eels (Anguilla rostrata), and juveniles are transported more than 5000 km back to the European and North African coasts. The two species have been regarded as classic textbook examples of panmixia, each comprising a single, randomly mating population. However, several recent studies based on continental samples have found subtle, but significant, genetic differentiation, interpreted as geographical or temporal heterogeneity between samples. Moreover, European and American eels can hybridize, but hybrids have been observed almost exclusively in Iceland, suggesting hybridization in a specific region of the Sargasso Sea and subsequent nonrandom dispersal of larvae. Here, we report the first molecular population genetics study based on analysis of 21 microsatellite loci in larvae of both Atlantic eel species sampled directly in the spawning area, supplemented by analysis of European glass eel samples. Despite a clear East–West gradient in the overlapping distribution of the two species in the Sargasso Sea, we only observed a single putative hybrid, providing evidence against the hypothesis of a wide marine hybrid zone. Analyses of genetic differentiation, isolation by distance, isolation by time and assignment tests provided strong evidence for panmixia in both the Sargasso Sea and across all continental samples of European eel after accounting for the presence of sibs among newly hatched larvae. European eel has declined catastrophically, and our findings call for management of the species as a single unit, necessitating coordinated international conservation efforts.©2011 Blackwell Publishing Ltd.

BUI, A.O.V., M. CASTONGUAY, P. OUELLET, J.-M SÉVIGNY, 2011. Searching for Atlantic Cod (Gadus morhua) spawning sites in the northwest Gulf of St Lawrence (Canada) using molecular techniques. ICES J. Mar. Sci., 68(5): 911-918 .

The overexploitation of Atlantic cod (Gadus morhua) in the Northwest Atlantic led to the collapse of most stocks and the demise of spawning components in the early 1990s. In the northern Gulf of St Lawrence, the spawning component of Northwest Atlantic Fishery Organization Division 4S was believed no longer to exist after the collapse. To verify this hypothesis, we used molecular techniques to identify cod, haddock, and witch flounder (CHW) eggs precisely, in an attempt to locate the potential remaining spawning sites for cod in the northwest Gulf. Ichthyoplankton surveys were conducted in spring from 2005 to 2008. Results were compared with those of surveys that took place in spring in the same area 20 years earlier to determine if there had been any changes in spawning location and egg abundance. Atlantic cod made up the majority (97 %) of CHW eggs identified. The presence of stage I cod eggs proved that there is still a cod spawning component in the northwest Gulf of St Lawrence, but egg abundance has declined by about an order of magnitude compared with the 1980s. There was no obvious difference in the location of cod spawning grounds between the two decades

TAMDRARI, H., M. CASTONGUAY, J.-C BRÊTHES, D. DUPLISEA, 2010. Density-independent and dependent habitat selection of Atlantic Cod (Gadus morhua) bases on geostatistical aggregation curves in the northern Gulf of St Lawrence. ICES J. Mar. Sci., 67(8): 1676-1686 .

Relationships were sought between local density and population abundance of Atlantic cod (Gadus morhua) in the northern Gulf of St Lawrence (Canada) over its entire area (4RS) and also within a subarea (4R) where the stock has concentrated since it collapsed during the early 1990s. Relationships were analysed using geostatistical aggregation curves computed within the two areas between years of contrasting abundance levels. The curves were interpreted in terms of four conceptual models of spatial dynamics: models D1 and D2, forced mainly by environmental heterogeneity, and models D3 and D4, in which individual behaviour is influenced by local density. Over the entire area, the cod population follows the D2 model for all years and age groups, and it is influenced by abiotic factors. Within the subarea, all four models applied, and the density-dependent basin model (D4) dominated from 2006 to 2008. The year 2006 seems to be pivotal because it coincides with the expansion of the cod population into its former area in the western Gulf (4S).©2010 International Council for the Exploration of the Sea. Published by Oxford Journals

GAUTHIER, J., M. CASTONGUAY, POWER, D., K. DWYER, 2010. Évaluation des stocks de sébastes (Sebastes fasciatus et S. mentella) des unités 1 et 2 en 2009. MPO, Secrétariat canadien de consultation scientifique, Avis scientifique, 2010/037, 22 p .

Click to see all the text

GAUTHIER, J., M. CASTONGUAY, D. POWER, K. DWYER, 2010. Assessment of redfish stocks (Sebastes fasciatus and S. mentella) in Units 1 and 2 in 2009. DFO, Canadian Science Advisory Secretariat, Science Advisory Report, 2010/037, 20 p .

Click to see all the text

BUI, A.O.V., P. OUELLET, M. CASTONGUAY, J.-C. BRÊTHES, 2010. Ichthyoplankton community structure in the northwest Gulf of St. Lawrence (Canada) : past and present. Mar. Ecol. Prog. Ser., 412: 189-205 .

Biodiversity can play an important role in the stability and resilience of ecosystems when these are faced with environmental change or anthropogenic impacts. Historically, the northwest Gulf of St. Lawrence had high fish egg and larval productivity. To assess changes in the ichthyoplankton community of this region, data from sampling surveys that were carried out in spring from 1985 to 1987 were compared with data from spring 2005 to 2007. Significant differences in ichthyoplankton abundances between the 2 decades and sampling times (May versus June) were revealed by multivariate analyses (nMDS, ANOSIM, PERMANOVA, and SIMPER) and univariate (ANOVA) analyses. Total ichthyoplankton abundance was lower in the 2000s than during the mid- 1980s. Although larval sandlance Ammodytes spp. abundances did not change significantly, other taxa, such as Stichaeidae larvae and H4B eggs (gadids and merlucciid hakes, rocklings, butterfish Peprilus triancanthus, windowpane Scophthalmus aquosus and Gulf Stream flounder Citharichthys arctifrons), became more abundant; the abundance of CHW eggs (cod Gadus morhua, haddock Melanogrammus aeglefinus, witch flounder Glyptocephalus cynoglossus), and redfish Sebastes spp. larvae generally declined by more than an order of magnitude. Greenland halibut Reinhardtius hippoglossoides larvae also appeared in the 2000s assemblages. This dominance shift in the ichthyoplankton community reflects the demise of large fish predators and the response of the non-commercial species. Our study provides much-needed new information concerning current biodiversity and productivity of the fish community in the Gulf of St. Lawrence and insights into changes influenced by groundfish collapse and environmental fluctuations.©2010 Inter-Research

DUFOUR, R., H. BENOIT, M. CASTONGUAY, J. CHASSÉ, L. DEVINE, P. GALBRAITH, M. HARVEY, P. LAROUCHE, S. LESSARD, B. PETRIE, L. SAVARD, C. SAVENKOFF, L. ST-AMAND, M. STARR, 2010. Ecosystem status and trends report: Estuary and Gulf of St. Lawrence ecozone. Rapport sur l’état et les tendances des écosystèmes : écozone de l’estuaire et du golfe du Saint Laurent. DFO, Canadian Science Advisory Secretariat, Research Document ; MPO, Secrétariat canadien de consultation scientifique, Document de recherche; 2010/030, 193 p .

Click to see all the text

This document was produced under the umbrella of the national ecosystem status and trends report program and deal with the estuary and gulf of St.Lawrence ecozone. It is structured around the status and trends of some important marine species and physico-chemical variables of the ecosystem. The national ecosystem status and trends report will support prioruty-setting for a national biodiversity agenda and will integrate national and provincial exosystem-bases information. It will report on many large terrestrial and marine ecozones.

RIEMANN, L., H. ALFREDSSON, M.M. HANSEN, T.D. ALS, T.G. NIELSEN, P. MUNK, K. AARESTRUP, G.E. MAES, H. SPARHOLT, M.I. PETERSEN, M. BACHLER, M. CASTONGUAY, 2010. Qualitative assessment of the diet of European eel larvae in the Sargasso Sea resolved by DNA barcoding. Biol. Letters, 6:819-822 .

European eels (Anguilla anguilla) undertake spawning migrations of more than 5000 km from continental Europe and North Africa to frontal zones in the Sargasso Sea. Subsequently, the larval offspring are advected by large-scale eastward ocean currents towards continental waters. However, the Sargasso Sea is oligotrophic, with generally low plankton biomass, and the feeding biology of eel larvae has so far remained a mystery, hampering understanding of this peculiar life history. DNA barcoding of gut contents of 61 genetically identified A. anguilla larvae caught in the Sargasso Sea showed that even the smallest larvae feed on a striking variety of plankton organisms, and that gelatinous zooplankton is of fundamental dietary importance. Hence, the specific plankton composition seems essential for eel larval feeding and growth, suggesting a linkage between eel survival and regional plankton productivity. These novel insights into the prey of Atlantic eels may furthermore facilitate eel larval rearing in aquaculture, which ultimately may replace the unsustainable use of wild-caught glass eels. ©2010 The royal Society

DUFOUR, R., H. BENOIT, M. CASTONGUAY, J. CHASSÉ, L. DEVINE, P. GALBRAITH, M. HARVEY, P. LAROUCHE, S. LESSARD, B. PETRIE, L. SAVARD, C. SAVENKOFF, L. ST-AMAND, M. STARR, 2010. Rapport sur l'état et les tendances des écosystèmes marins canadiens en 2010. MPO, Secrétariat canadien de consultation scientifique, Avis scientifique, 2010/030(révisé), 43 p .

Click to see all the text

CASTONGUAY, M, S. DUBÉ, 2010. Compte rendu de la réunion du Processus consultatif scientifique de la région du Québec portant l’évaluation des stocks de hareng de la côte ouest de Terre-Neuve (4R);Proceedings of the Quebec Region Science Advisory Process on the Assessment of the West coast of Newfoundland herring (4R) Stocks. MPO, Secrétariat canadien de consultation scientifique, Série des comptes rendus ; DFO, Canadian Science Advisory Secretariat, Proceedings Series, 2010/022, 21 p .

Click to see all the text

DUFOUR, R., H. BENOIT, M. CASTONGUAY, J. CHASSÉ, L. DEVINE, P. GALBRAITH, M. HARVEY, P. LAROUCHE, S. LESSARD, B. PETRIE, L. SAVARD, C. SAVENKOFF, L. ST-AMAND, M. STARR, 2010. 2010 Canadian marine ecosystem status and trends report. Advis. Sec. Sci. Advis. Rep. 2010/030(Revised), 38 p .

Click to see all the text

BONHOMMEAU, S., M. CASTONGUAY, E. RIVOT, R. SABATIÉ, O. LE PAPE, 2010. The duration of migration of Atlantic Anguilla larvae. Fish Fish., 11(3): 289-306 .

Oceanic larvae of the European (Anguilla anguilla) and American (A. rostrata) eels have to cross the Atlantic Ocean from the Sargasso Sea to European or North American coasts before entering continental habitats. In some European rivers, eel recruitment is now <1 % of levels in the 1980s. A better understanding of the effects of anthropogenic pressures and environmental fluctuations on eel larvae and subsequent recruitment is a prerequisite to build efficient management plans. The present paper provides insight into the critical oceanic phase of the eel life cycle with a focus on the duration of the larval migration whose estimates varies between 7 months and more than 2 years in both species. Does this range correspond to a natural variability in larval duration or does it stem from methodological artefacts? We first review the different methods used to estimate the duration of larval migration and critically describe their possible sources of misinterpretation. We then evaluate the consistency of these methods with the current knowledge about the ecology and physiology of eel larvae and the physical oceanography. While a moderate discrepancy in migration duration was found between methods for the American eel, the discrepancy was large in the European eel. In this species, otolith microstructure studies indicated migration durations between 7 and 9 months, while other methods pointed to durations of about 2 years. We show that estimates in favour of a long migration duration seem more robust to methodological caveats than methods estimating short durations of migration.©2010 Wiley

ROBERT, D., M. CASTONGUAY, L. FORTIER, 2009. Effects of preferred prey density and temperature on feeding success and recent growth in larval mackerel of the southern Gulf of St. Lawrence. Mar. Ecol. Prog. Ser., 377: 227-237 .

We evaluated the effects of preferred prey density and temperature on the feeding success and recent growth of Atlantic mackerel larvae from 4 consecutive annual cohorts (1997 to 2000) in the southern Gulf of St. Lawrence. Individual feeding success (residuals of the linear regression of preferred prey carbon in the gut content on larval length) and recent growth (average width of last 3 otolith increments) were determined for a stratified subsample of larvae in each year and among different length classes. The density of preferred prey best explained variations in feeding success and growth in first-feeding larvae (<7 mm), while temperature was the main source of growth variability during older larval stages. The feeding success and growth of early larvae increased with the density of Pseudocalanus sp. Nauplii until a similar satiation threshold of 1 μgC l-1. Recent growth increased linearly with temperature during the late larval stage, without any indication of a temperature optimum. These results suggest that high abundance of the preferred prey at the onset of exogenous feeding and relatively warm temperature during the larval growth season are important prerequisites for the emergence of a strong year class in Atlantic mackerel.©2009 Inter-Research

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.

BONHOMMEAU, S., O. LE PAPE, D. GASCUEL, B. BLANKE, A.-M. TRÉGUIER, N. GRIMA, Y. VERMARD, M. CASTONGUAY, E. RIVOT, 2009. Estimates of the mortality and the duration of the trans-Atlantic migration of European Eel Anguilla anguilla leptocephali using a particle tracking model. J. Fish. Biol., 74(9): 1891-1914 .

Using Lagrangian simulations, based on circulation models over three different hydroclimatic periods in the last 45 years in the North Atlantic Ocean, the trans-Atlantic migration of the European Eel Anguilla anguilla leptocephali was simulated via the passive drift of particles released in the spawning area. Three different behaviours were modelled: drifting at fixed depth, undergoing a vertical migration or choosing the fastest currents. Simulations included mortality hypotheses to estimate a realistic mean migration duration and relative survival of A. anguilla larvae. The mean migration duration was estimated as 21 months and the mortality rate as 3•8 per year, i.e. <0•2 % of A. anguilla larvae may typically survive the trans-Atlantic migration.©2009 The Fisheries Society of the British Isles

CÔTÉ, C.L., M. CASTONGUAY, G. VERREAULT, L. BERNATCHEZ, 2009. Differential effects of origin and salinity rearing conditions on growth of Glass Eels of the American eel Anguilla rostrata : implications for socking programmes. J. Fish. Biol., 74: 1934-1948 .

In this study, growth patterns were monitored in controlled fresh and brackish water (BW) conditions for 7 months during Anguilla rostrata Glass Eel and elver stages. Null hypotheses tested were that there is no significant difference in growth between Glass Eels (1) collected from two geographic regions typified by different sex ratios, (2) reared in fresh and BW and (3) due to origin × salinity interactions. It was found that young A. rostrata from Mira River (MR, Cape Breton, Nova Scotia, Canada, an area where both males and females occur) grew faster than those from Grande-Rivière-Blanche (Québec, Canada, an area where population are highly skewed towards females; 99–100&ndsp;%). Anguilla rostrata from both origins also grew faster in BW, although there was a trend for origin × salinity interactions whereby this effect was more pronounced for fish from the MR. The results support the hypothesis that salinity can influence growth patterns, as possibly can quantitative genetic differences between A. rostrata Glass Eels from different origins. Possible explanations for these patterns and potential consequences for sex determination and translocation programmes are discussed.©2009 The Fisheries Society of the British Isles

DUTIL, J.-D., P. DUMONT, D.K. CAIRNS, P.S. GALBRAITH, G. VERREAULT, M. CASTONGUAY, S. PROULX, 2009. Anguilla rostrata glass eel migration and recruitment in the estuary and Gulf of St Lawrence. J. Fish. Biol., 74: 1970-1984 .

This study describes catches of Anguilla rostrata glass eels and associated oceanographic conditions in the St Lawrence Estuary and Gulf. Ichthyoplankton survey data suggest that they enter the Gulf primarily in May, migrate at the surface at night, and disperse broadly once they have passed Cabot Strait. T hey arrive in estuaries beginning at about mid-June and through the month of July. Migration extends west up to Quebec City, in the freshwater zone of the St Lawrence Estuary, 1000 km west of Cabot Strait. Anguilla roslrata glass eels travel between Cabot Strait and receiving estuaries at a straight-line ground speed of c. 10–15 km day-1. Catches of fish per unit effort in estuaries in the St Lawrence system are much lower than those reported for the Atlantic coast of Canada. Low abundance of A. rostrata glass eels in the St Lawrence system may be due to cold surface temperatures during the migration period which decrease swimming capacity, long distances from the spawning ground to Cabot Strait and from Cabot Strait to the destination waters (especially the St Lawrence River), complex circulation patterns, and hypoxic conditions in bottom waters of the Laurentian Channel and the St Lawrence Estuary.©2009 The Fisheries Society of the British Isles

AARESTRUP, K., F. OKLAND, M.M. HANSEN, D. RIGHTON, P. GARGAN, M. CASTONGUAY, L. BERNATCHEZ, P. HOWEY, H. SPARHOLT, M.I. PEDERSEN, R.S. McKINLEY, 2009. Oceanic spawning migration of the European Eel (Anguilla anguilla). Science (Wash.), 325(5948): 1660 .

European eels (Anguilla anguilla) undertake a ˜5000-kilometer (km) spawning migration from Europe to the Sargasso Sea. The larvae are transported back to European waters by the Gulf Stream and North Atlantic Drift. However, details of the spawning migration remain unknown because tracking eels in the Atlantic Ocean has, so far, eluded study. Recent advances in satellite tracking enable investigation of migratory behavior of large ocean-dwelling animals. However, sizes of available tags have precluded tracking smaller animals like European eels. Here, we present information about the swimming direction, depth, and migratory behavior of European eels during spawning migration, based on a miniaturized pop-up satellite archival transmitter. Although the tagging experiment fell short of revealing the full migration to the Sargasso Sea, the data covered the first 1300 km and provided unique insights.©2009 American Association for the Advancement of Science

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.

ROBERT, D., M. CASTONGUAY, L. FORTIER, 2008. Effects of intra- and inter-annual variability in prey field on the feeding selectivity of larval Atlantic mackerel (Scomber scombrus). J. Plankton Res., 30(6): 673-688 .

We identified to the lowest taxonomical level possible the preferred prey of Atlantic mackerel larvae from the southern Gulf of St Lawrence and assessed the extent to which prey selectivity varied within and among years. Mackerel larvae and their zooplankton prey were sampled in the summer of four consecutive years (1997-2000). The nauplii of the calanoid copepod Pseudocalanus sp. Strongly dominated the diet of larvae <7 mm both in terms of numbers and carbon content, whereas larvae ≥7 mm mainly fed on fish larvae (including conspecifics) and cladocerans. Chesson's alpha index revealed strong selectivity in all years for Pseudocalanus sp. Nauplii in first-feeding larvae. Selectivity shifted to cladocerans and fish larvae around a body length of 7 mm. Intra- and inter-annual prey selectivity changes were mainly observed for alternative prey, during the period surrounding the shift in diet from small to large prey. Our results underscore the importance of considering the availability of the main prey Pseudocalanus sp. Nauplii (early larval stage) as well as cladocerans and fish larvae (late larval stage), rather than the entire prey field in the future assessment of the role played by prey availability on larval mackerel vital rates.©2008 The Authors & Oxford University Press

CASTONGUAY, M., S. PLOURDE, D. ROBERT, J.A. RUNGE, L. FORTIER, 2008. Copepod production drives recruitment in a marine fish. Can. J. Fish. Aquat. Sci., 65: 1528-1531 .

Predicting fluctuations in recruitment of commercial marine fish remains the Holy Grail of fisheries science. In previous studies, we identified statistical relationships linking Atlantic mackerel (Scomber scombrus) recruitment to regional climate, zooplankton biomass, and the production of copepod nauplii over a decade (1982-1991) that included the exceptionally strong year class of 1982. Here we tested the validity of these relationships by adding a second decade (1992-2003) of observations that includes another exceptional year class in 1999. We provide the first field-based evidence linking availability of plankton prey in the sea to early growth of larval fish and to year-class strength in a commercially exploited marine fish. Recruitment is shown to strongly depend on production of the copepod nauplii species that contribute to the diet of mackerel larvae. Both strong year classes were characterized by exceptionally high availability of these specific prey. We suggest that mackerel recruitment can be anticipated 3 years in advance based on prey availability during the first weeks of planktonic life and predict a strong year class for fish hatched in 2006.©2008 NRC Canada

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.

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.

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.

ROBERT, D., M. CASTONGUAY, L. FORTIER, 2007. Early growth and recruitment in Atlantic mackerel Scomber scombrus : discriminating the effects of fast growth and selection for fast growth. Mar. Ecol. Prog. Ser., 337: 209-219 .

We tested the hypothesis that strong recruitment in Atlantic mackerel Scomber scombrus occurs only in years when larval growth is fast and predation pressure–as measured by selection for fast growth–is weak. Four annual cohorts of larvae (1997, 1998, 1999 & 2000) were sampled on the Magdalen Shallows, southern Gulf of St. Lawrence, and 1 yr old mackerel juveniles were sampled the year after in the mackerel fishery of the southern Gulf. The early larval growth trajectories of both larvae and juveniles were back-calculated from the analysis of the sagittal otolith. Interannual differences in growth measured in the larvae persisted in the juveniles. The growth of larvae was significantly higher in 1999, an exceptional year class, than in the 3 other weak year classes. Surviving juveniles of the strong 1999 and the weak 1997 year classes grew equally fast during the first 40 d of larval life, but selection for fast growth was mild in 1999 and severe in 1997. We conclude that fast early growth measured in 1 yr old juveniles reflected fast growth of the entire larval population in 1999, and strong selective mortality against slow-growing larvae in 1997. Early growth was slow in larvae and juveniles of the weak 1998 (mild selection) and 2000 (no selection) year classes. Consistent with the hypothesis, the combination of fast growth and weak selection for fast growth unique to the 1999 cohort resulted in exceptional recruitment. ©2007 Inter-Research

CASTONGUAY, M., 2007. Prise en considération des changements dans la mortalité naturelle au sein des stocks de morue du golfe du Saint-Laurent. MPO, Secrétariat canadien de consultation scientifique, Avis scientifique, 2007/002, 13 p .

Click to see all the text

CASTONGUAY, M., 2007. Accounting for changes in natural mortality in Gulf of St Lawrence cod stocks. DFO, Canadian Science Advisory Secretariat, Science Advisory Report, 2007/002, 10 p .

Click to see all the text

CASTONGUAY, M., S. VALOIS, 2007. Zones d'importance écologique et biologique pour les poissons démersaux dans le nord du golfe du Saint-Laurent ; Ecologically and biologically significant areas for demersal fishes in the northern Gulf of St. Lawrence. MPO, Secrétariat canadien de consultation scientifique, Document de recherche ; DFO, Canadian Science Advisory Secretariat, Research Document, 2007/014, 30 p .

Click to see all the text

This report presents candidate ecologically and biologically significant areas for demersal fish (groundfish) species in the northern Gulf of St. Lawrence. Spawning areas, regions of juvenile concentrations, feeding sites, migration routes, and seasonal refugia were evaluated according to their unicity, their concentration, and their consequences on adaptive significance. Of the eight zones selected, six were identified based on spatial distribution of juvenile stages in summer while a seventh was identified because of its species richness in summer and an eighth because it represents a known cod migratory corridor. The most important zones were the St. Lawrence maritime estuary, Newfoundland’s West Coast including the Esquiman Channel, and the Laurentian Channel in winter.

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 .

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 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 .

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 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)

DUPLISEA, D.E., M. CASTONGUAY, 2006. Comparison and utility of different size-based metrics of fish communities for detecting fishery impacts. Can. J. Fish. Aquat. Sci., 63: 810-820 .

The use of fish community indicators based on size spectra has become popular in the development of an ecosystem approach to fisheries. Size spectrum theory arose from basic ecological work on energy flow, predator-prey interactions, and biomass standing stock and was later applied to fish communities as length-frequency analysis. A multitude of size spectrum indicators have resulted, but it is not clear if they all present similar information. Here we develop a simple framework describing what four size spectra indicators suggest about fish communities, their likely response to fisheries exploitation, their ecological interpretation, and some of their biases. We examined indicators for scientific survey data from six exploited North Atlantic fish communities for the information that they reveal about each community. Each indicator revealed different information and had different biases. Combining indicators for the most impacted system (owing to fisheries and environmental change), the eastern Scotian Shelf, revealed a pattern analogous to Holling’s ecological cycle of exploitation, conservation, release, and reorganisation. If this analogy is generally valid, then it suggests that collapsed fish communities are more susceptible to chance events, and recovery is not directly reversible and may not be recoverable (to previous known state) at all if the system moves to an alternative cycle.

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 .

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 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.

CYR, C., D. BERNIER, M. CASTONGUAY, 2006. Compte rendu de l'atelier zonal sur les nouveaux éléments probants concernant la question de la distinction des stocks de sébaste des Unités 1 et 2 dans le contexte du mode de gestion actuelle, 9 février 2006, Institut Maurice-Lamontagne, Mont-Joli, Qc ; Proceedings of the Zonal Workshop on new evidence regarding the issue of redfish stock discrimination between Units 1 and 2 in the context of the current management practice, 9 February 2006, Maurice Lamontagne Institute, Mont-Joli, Qc. MPO, Secrétariat canadien de consultation scientifique, Série des comptes rendus ; DFO, Canadian Science Advisory Secretariat, Proceedings Series, 2006/019, 13 p .

Click to see all the text

A zonal workshop of one-day was held in order to examine new elements concerning the distinction of redfish stocks in Units 1 and 2 within the context of the current management approach. During the meeting held on February 9th, 2006, participants studied the most recent data concerning population structure of Northwest Atlantic redfish stocks. Specifically, genetic and geometric morphometric data as well as data on the elemental composition of otoliths were examined. The discussions that were held during the workshop were not entirely conclusive as to the biological relevance of the management units currently used for redfish. Nevertheless, it was agreed to that this point be added to the agenda of a future workshop, which should be held within a few months.

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)

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.

MÉTHOT, R., M. CASTONGUAY, Y. LAMBERT, C. AUDET, S.E. CAMPANA, 2005. Spatio-temporal distribution of spawning and stock mixing of Atlantic cod from the northern Gulf of St. Lawrence and southern Newfoundland stocks on Burgeo Bank as revealed by maturity and trace elements of otoliths. J. Northwest Atl. Fish. Sci., 36: 31-42 .

Click to see all the text

Atlantic cod (Gadus morhua) from the northern Gulf of St. Lawrence stock (NAFO Subdivisions 3Pn and Divisions 4RS) overwinter in deep waters east of Cabot Strait. During winter and spring, cod from this stock mix with fish from the southern Newfoundland cod stock (NAFO Subdiv. 3Ps), especially on Burgeo Bank. However, the degree and exact period of mixing are not known. The reproductive activity of female cod in the northern Gulf and on Burgeo Bank was examined to identify spawning areas, timing of reproduction, and stock mixing. From April to July 2001, spawning was studied visually (n = 2 129 adult females) and histologically (n = 450 adult females) by following monthly changes in the frequency distributions of maturity stages of female cod. Spawning was more advanced in the northern Gulf than in the other areas in April. Few spawning females were caught during the study on Burgeo Bank, indicating that this region was not a major spawning area in spring 2001. The relative frequencies of fish in spawning condition in April and May were different between Burgeo Bank (Subdiv. 3Ps) and the Gulf (Subdiv. 3Pn and Div. 4R). Trace element analyses of otoliths of maturing females collected on Burgeo Bank in late April were used to determine their stock origin. Otoliths of spawning females from the northern Gulf and Burgeo Bank were used as reference groups. The trace element results indicated that a substantial fraction (41-52 %) of the maturing female cod sampled on Burgeo Bank in late April 2001 originated from the northern Gulf of St. Lawrence stock.©2005 Northwest Atlantic Fisheries Organization

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 .

Click to see all the text

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

DUTIL, J.-D., J. GAUTHIER, A. FRÉCHET, M. CASTONGUAY, Y. LAMBERT, P. OUELLET, 2005. Northern Gulf of St. Lawrence (NAFO 3Pn and 4RS). Pages 105-113 in K. Brander (ed.). Spawning and life history information for North Atlantic cod stocks. International Council for the Exploration of the Sea (ICES Coop. Res. Rep., 274) .

Click to see all the text

GAUTHIER, J., M. CASTONGUAY, 2005. Flétan du Groenland du golfe du Saint-Laurent (4RST) en 2004. MPO, Secrétariat canadien de consultation scientifique, Avis scientifique, 2005/012, 9 p .

Click to see all the text

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

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 .

Click to see all the text

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

GAUTHIER, J., M. CASTONGUAY, 2005. Gulf of St. Lawrence (4RST) Greenland halibut in 2004. DFO, Canadian Science Advisory Secretariat, Science Advisory Report, 2005/012, 9 p .

Click to see all the text

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

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 .

Click to see all the text

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.

FRIEDLAND, K.D., D.G. REDDIN, M. CASTONGUAY, 2003. Ocean thermal conditions in the post-smolt nursery of North American Atlantic salmon. ICES J. Mar. Sci., 60: 343-355 .

SWAIN, D.P., A.F. SINCLAIR, M. CASTONGUAY, G.A. CHOUINARD, K.F. DRINKWATER, L.P. FANNING, D.S. CLARK, 2003. Density-versus temperature-dependent growth of Atlantic cod (Gadus morhua) in the Gulf of St. Lawrence and on the Scotian Shelf. Fish. Res., 59: 327-341 .

SAVENKOFF, C., M. CASTONGUAY, 2003. L'écosystème du nord du Golfe du Saint-Laurent (milieu des années 1980). Naturaliste can., 127(1): 84-88 .

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 .

COMEAU, L.A., S.E. CAMPANA, M. CASTONGUAY, 2002. Automated monitoring of a large-scale cod (Gadus morhua) migration in the open sea. Can. J. Fish. Aquat. Sci., 59: 1845-1850 .

The migration patterns of marine fishes are poorly known, in part owing to the technical limitations associated with tracking the movements of animals in deep water. Here we document a large-scale, directed, migration of Atlantic cod (Gadus morhua) off eastern Canada. Our approach was based on the acoustic tagging of 126 fish and the deployment of 69 subsurface receivers, stretching over a 160-km distance along the edge of the Laurentian Channel. After 1 year of automated recording, we found that 65 % of the fish migrated out of coastal waters in two distinct runs during the summer-autumn period. The offshore-migrating fish overwintered in deep Laurentian Channel waters, returning inshore in April. Individual migration routes and migration timing were variable, indicating that the cod did not aggregate in large schools during the seasonal migration events.

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.

DUTIL, J.-D., M. CASTONGUAY, D. GILBERT, D. GASCON, 2002. Production analyses for cold-water and warm-water stocks and their use to predict surplus production. Pages 50-54 in N. Anderson, G. Ottersen & D. Swain (ed.). Report of the ICES/GLOBEC Workshop on the Dynamics of Growth in Cod. International Council for the Exploration of the Sea (ICES Coop. Res. Rep., 252 .

Surplus and net production per capita became nil or negative in the mid-1980s in the northern Gulf of St. Lawrence (Dutil et al., 1999). This situation was partly explained by a marked decline in growth production and is consistent with smaller sizes-at-age (Chouinard and Fréchet 1994) but also lower condition factor values during the same period (Lambert and Dutil 1997). The nutritional condition of cod in the Gulf of St. Lawrence varies markedly both seasonnally and annually (Lambert and Dutil 1997, Schwalme and Chouinard 1999) and this has been found to be associated with changes in swimming capacity (unpublished data), reproductive investment (Lambertet al., 2000, Lambert and Dutil 2000) and risks of natural mortality (Dutil and Lambert 2000; and unpublished data). Positive slopes between size-at-age and temperature suggested faster growth rates at higher temperatures for northern Gulf cod, but correlations between size-at-age and temperature were not significant (Dutil et al., 1999). Production analyses conducted for the northern Gulf of St. Lawrence were extended to other stocks. Growth production was assessed in order to determine its variability among and within stocks as a first step to measure its impact on the stock biomass.©2008 ICES

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 .

LACOSTE, K.N., J. MUNRO, M. CASTONGUAY, F.J. SAUCIER, J.A. GAGNÉ, 2001. The influence of tidal streams on the pre-spawning movements of Atlantic herring, Clupea harengus L., in the St. Lawrence estuary. ICES J. Mar. Sci., 58: 1286-1298 .

CASTONGUAY, M., 2000. The northern Gulf of St. Lawrence cod stock - background information on recruitment. DFO, Canadian Stock Assessment Secretariat, Research Document ; MPO, Secrétariat canadien de consultation scientifique, Document de recherche, 2000/106, 8 p .

Click to see all the text

As part of a Workshop on cod recruitment, the FOC (Fisheries Oceanography Committee) reviewed recent trends in recruitment for all Canadian cod stocks to determine if poor recruitment could account for the slow recovery of stocks. Spawning stock biomass of northern Gulf of St. Lawrence cod (3Pn4RS) gradually declined to a minimum in 1994 and has slowly recovered since. Recruitment has been weak through the 1990s. There appears to be a fairly good stock/recruitment relationship in this stock. Recruitment rate (i.e., recruitment given the observed level of spawning stock biomass) has risen in the 1990s, which could indicate a compensatory response of the stock to low abundance levels. Hence the slow recovery of the stock cannot be accounted for by low recruitment given the observed level of spawning stock biomass. Total mortality of adult cod calculated from survey data has been around 0.5 from 1994 to 1997. Taking fishing mortality into account suggests that natural mortality has been between 0.3 and 0.4, which supports the current natural mortality value of 0.4 assumed for the stock in sequential population analysis. There has been a pronounced decline in size-at-age of cod in the late 1980s, early 1990s, indicative of a decline in surplus production.

DUTIL, J.-D., M. CASTONGUAY, D. GILBERT, D. GASCON, 2000. Production analyses for cold-water and warm-water stocks and their use to predict surplus production. Pages 61-65 in N.G. Andersen, G. Ottersen & D.P. Swain (ed.). Report of the ICES/GLOBEC workshop on the dynamics of growth in cod, Dartmouth, Canada, 8-10 May 2000 (ICES C.M., 2000/C:12) .

CASTONGUAY, M., C. ROLLET, A. FRÉCHET, P. GAGNON, D. GILBERT, J.-C. BRÊTHES, 1999. Distribution changes of Atlantic cod (Gadus morhua L.) in the northern Gulf of St. Lawrence in relation to an oceanic cooling. ICES J. Mar. Sci., 56: 333-344 .

RUNGE, J.A., M. CASTONGUAY, Y. De LAFONTAINE, M. RINGUETTE, J.-L. BEAULIEU, 1999. Covariation in climate, zooplankton biomass and mackerel recruitment in the southern Gulf of St. Lawrence. Fish. Oceanogr., 8: 139-149 .

DUTIL, J.-D., M. CASTONGUAY, D. GILBERT, D. GASCON, 1999. Growth, condition, and environmental relationships in Atlantic cod (Gadus morhua) in the northern Gulf of St. Lawrence and implications for management strategies in the Northwest Atlantic. Can. J. Fish. Aquat. Sci., 56(10): 1818-1831 .

Northern Gulf of St. Lawrence Atlantic cod (Gadus morhua) is one of several stocks that collapsed in eastern Canada following a long period of intensive exploitation. Surplus and net production per capita became nil or negative in the mid-1980s so that any level of exploitation would have caused a decline of the stock. This was partly explained by a marked decline in growth production and is consistent with smaller sizes-at-age but also lower condition factor values during the same period. Correlations between size-at-age and temperature were not significant when corrected for autocorrelation, but slopes were always positive, suggesting higher growth rates at higher temperatures. Smaller sizes-at-age in the 1980s were not associated with changes in the fishery or increased fishing mortality, nor were they consistent with the density-dependence hypothesis. Lengths at age 8 decreased by more than 10 cm as the stock decreased 10-fold in abundance. While size-at-age and temperature covary in cod when all stocks are examined, size-temperature relationships are not as clear if the analysis is restricted to cold-water stocks, possibly because of differences in food availability. Biological production varies from year to year and among stocks and should be taken into consideration when managing fisheries in variable or extreme environments.

GLUYAS-MILLAN, M.G., M. CASTONGUAY, C. QUINONEZ-VELAZQUEZ, 1998. Growth of juvenile Pacific mackerel, Scomber japonicus in the Gulf of California. Sci. Mar. ((Barc.), 62(3): 225-231 .

CASTONGUAY, M., Y. De LAFONTAINE, J.A. RUNGE, 1998. Annual and spatial variability in zooplankton biomass and species composition, and in eggs and larvae of mackerel and cod in the southern Gulf of St. Lawrence between 1982 and 1991. Can. Data Rep. Fish. Aquat. Sci., 1035, 86 p .

Click to see all the text

Between 1982 and 1991, an annual survey of egg production of Atlantic mackerel (Scomber scombrus L.) was conducted in late June/early July in the southern Gulf of St. Lawrence to assess mackerel abundance. Plankton samples were first sorted for fish eggs and larvae and then analysed for zooplankton biomass and species composition. This data series offered an opportunity to investigate relationships between mackerel recruitment and zooplankton biomass /species composition. The objective of this report is to make available the zooplankton dataset that has been examined as part of this investigation. The report presents maps for each year of 1) spatial distributions of zooplankton biomass split into four size classes; 2) zooplankton species composition (total and female Calanus finmarchicus, female Pseudocalanus sp., and female Temora longicornis) for four of the ten years (1982, 1985, 1987, and 1990); 3) spatial distributions of eggs and larvae of mackerel and cod (Gadus morhua L.) and 4) near-surface (0-10 m) temperature (1982-1991) and salinity (1987-1991) patterns. (D.B.O.).

CASTONGUAY, M., D.G. CYR, 1998. Effects of temperature on spontaneous and thyroxine-stimulated locomotor activity of Atlantic cod. J. Fish Biol., 53(2): 303-313 .

CASTONGUAY, M., P.V. HODSON, C.M. COUILLARD, 1998. Chemical contamination, habitat loss and potential impact of oceanic factors on American eel recruitment in the St. Lawrence River. Pages 3-5 in The American eel in eastern Canada : stock status and management strategies : proceedings of Eel Workshop, January 13-14, 1997, Quebec City, QC (Can. Tech. Rep. Fish. Aquat. Sci., 2196) .

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 .

OUELLET, P., Y. LAMBERT, M. CASTONGUAY, 1997. Spawning of Atlantic cod (Gadus morhua L.) in the northern Gulf of St. Lawrence : a study of adult and egg distributions and characteristics. Can. J. Fish. Aquat. Sci., 54: 198-210 .

From 1993 to 1995, Atlantic cod (Gadus morhua) egg abundance and distribution, fisheries acoustic surveys, and analysis of trawl catches provided evidence of spawning for the northern Gulf of St. Lawrence cod stock at the same location off Newfoundland's west coast. From the relative proportion of spent fish and various developmental stages of cod eggs, spawning could not have started before the end of March or early April. Spawning started while cod were in dense shoals following a prespawning migration from Cabot Strait. Larger cod started to spawn earlier than smaller cod. In May 1994, cod dispersed soon after spawning began, and most of the spawning activity probably occurred as the fish migrated and scattered within the northern Gulf. Stage 1 cod eggs were distributed throughout the water column but higher concentrations were observed within the cold (<0 °C) layer of the Gulf each year. It is proposed that water temperature could have a dominant influence on determination of year-class strength in the northern Gulf via its effect on egg development and survival.

COUILLARD, C.M., P.V. HODSON, M. CASTONGUAY, 1997. Correlations between pathological changes and chemical contamination in American eels, Anguilla rostrata, from the St. Lawrence River. Can. J. Fish. Aquat. Sci., 54: 1916-1927 .

American eel (Anguilla rostrata) from the St. Lawrence River are heavily contaminated with chemicals that may be associated with increased incidence of disease and reproductive impairment. The relationship between tissue mirex concentration and body mass was used to separate eels into two groups : the proportion of eels migrating from contaminated areas (Lake Ontario and upper St. Lawrence River) increased as the migration season progressed. Vertebral malformations and basophilic foci in the liver (preneoplastic lesions) were more frequent at the end of the migratory season, when the eels were more heavily contaminated with organochlorine compounds. In contrast, mesenteric nematodes were more common in the first week of the season, when eels were less contaminated. Diameters and percentages of different stages of oocytes, and density and surface area of pigmented macrophage aggregates in the spleen, did not vary among weeks. While basophilic foci are specific biomarkers of exposure to environmental contaminants, vertebral malformations may be caused by a variety of other anthropogenic or natural factors.

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 .

CLAY, A., M. CASTONGUAY, 1996. in situ target strengths of Atlantic cod (Gadus morhua) and Atlantic mackerel (Scomber scombrus) in the Northwest Atlantic. Can. J. Fish. Aquat. Sci., 53: 87-98 .

The accurate determination of target strength (TS) is essential in the conversion of area backscattering to fish biomass. We present the first detailed in situ TS measurements of Atlantic cod (Gadus morhua) and Atlantic mackerel (Scomber scombrus) in the Northwest Atlantic. Mean total lengths of cod and mackerel were 52 and 38 cm, respectively. The mean daytime and nighttime in situ TS distributions (split-beam method) of cod were -35.5 (b20=-69.8) and -35.2 decibels (dB) (b20=-69.5), respectively. There was a depth stratification of cod TS at night, as mean in situ TS was -31.7 dB between 140 and 220 m and -35.8 dB between 220 and 300 m. We argue that the effect of depth on swim-bladder inflation is primarily responsible for the lower cod TS near the bottom than higher up in the water column. Analysis of the same TS data in split-beam or single-beam mode yielded similar distributions, showing the reliability of the single-beam method. The mean in situ TS (single-beam method) of mackerel was -56.4 dB (b20=-88.0), with no day-night difference.

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.

CASTONGUAY, M., D. GILBERT, 1995. Effects of tidal streams on migrating Atlantic mackerel, Scomber scombrus L. ICES J. Mar. Sci., 52: 941-954 .

CASTONGUAY, M., P.V. HODSON, C. MORIARTY, 1994. Is there a role of ocean environment in American and European eel decline. ICES C.M., 1994/Mini:06, 20 p .

HODSON, P.V., M. CASTONGUAY, C.M. COUILLARD, C. DESJARDINS, E. PELLETIER, R. McLEOD, 1994. Spatial and temporal variations in chemical contamination of American eels, Anguilla rostrata, captured in the estuary of the St. Lawrence River. Can. J. Fish. Aquat. Sci., 51: 464-478 .

CASTONGUAY, M., P.V. HODSON, C.M. COUILLARD, M.J. ECKERSLEY, J.-D. DUTIL, G. VERREAULT, 1994. Why is recruitment of the American eel, Anguilla rostrata, declining in the St. Lawrence River and Gulf. Can. J. Fish. Aquat. Sci., 51: 479-488 .

CASTONGUAY, M., P.V. HODSON, C. MORIARTY, K.F. DRINKWATER, B.M. JESSOP, 1994. Is there a role of ocean environment in American and European eel decline. Fish. Oceanogr., 3: 197-203 .

BEAULIEU, J.-L., M. CASTONGUAY, J.-P. BOUDREAU, 1993. Essais de pêche au maquereau au chalut pélagique. Rapp. can. ind. sci. halieut. aquat., 216, 17 p .

Click to see all the text

A fishing experiment for mackerel (Scomber scombrus) using a pelagic trawl equipped with a net positioning system was conducted in the Baie des Chaleurs on board the CSS Calanus II. From 20 to 24 August 1992, 8,900 (19,600 pounds) and 3,855 (8,500 pounds) kilograms of mackerel and herring were caught, respectively. Two thirds of herring catches were made at night. The mean length of mackerel captured was 334.4 mm with a range of 205 to 441 mm. Fuel cost could have been lower and mackerel catches higher if less time has been wasted travelling because of a lack of space to store the mackerel.

CASTONGUAY, M., J.-L. BEAULIEU, 1993. Development of a hydroacoustic abundance index for mackerel in Cabot Strait. DFO, Atlantic Fisheries, Research Document, 93/12, 24 p .

D'AMOURS, D., M. CASTONGUAY, 1992. Spring migration of Atlantic mackerel, Scomber scombrus, in relation to water temperature through Cabot Strait (Gulf of St. Lawrence). Environ. Biol. Fishes, 34: 393-399 .

CASTONGUAY, M., G.A. ROSE, W.C. LEGGETT, 1992. Onshore movements of Atlantic mackerel (Scomber scombrus) in the northern Gulf of St. Lawrence : associations with wind-forced advections of warmed surface waters. Can. J. Fish. Aquat. Sci., 49: 2232-2241 .

HODSON, P.V., C. DESJARDINS, É. PELLETIER, M. CASTONGUAY, R. McLEOD, C.M. COUILLARD, 1992. Decrease in chemical contamination of American eels (Anguilla rostrata) captured in the Estuary of the St. Lawrence River. Can. Tech. Rep. Fish. Aquat. Sci., 1876, 57 p .

Click to see all the text

American eels, Anguilla rostrata, are catadromous, and grow to maturity in Lake Ontario and in tributaries to the St. Lawrence River. Concern for mass mortalities of adult eels, high levels of chemical contamination, and a recent decline of recruitment prompted a study of the role of contaminants in the health of eels, the role of eels as vectors of contaminants to Beluga whales (Delphinapterus leucas) and the changes in contamination since an earlier large scale survey in 1982. Mercury, PCB, mirex and pesticide levels were measured in migratory adult eels in Kamouraska, Québec. Similar analyses were conducted on two eel samples from fishermen in Cacouna and Saint-Irénée, and on a control eel sample from a small tributary of the north shore of the St. Lawrence Estuary. Dioxins, furans and PAH concentrations were also determined on a small number of fish. Results indicate that eels from the upper St. Lawrence River/Lake Ontario were much more contaminated with PCBs, mirex and pesticides than the control population; concentrations did not vary among sites on the St. Lawrence River. Levels of PCBs and mirex have declined by 68 and 56 % respectively since 1982. Only 36 % of eels analyzed exceeded the guidelines for PCBs in fish, compared to 80 % in 1982; for mirex, the percentage declined from 52 % in 1982 to 29 % in 1990. Levels of PCBs, mirex and pesticides varied among weeks with a slight trend of increasing concentrations towards the end of the migration. Concentrations of PAH, dioxins and furans were usually less than their detection limits, and well below any guidelines. These results suggest that the risk of organic chemical toxicity to Belugas from consuming eels is declining from year to year. Mercury levels were constant among sites and times, indicating that accumulation originates mostly from natural sources or atmospheric deposition.

SIMARD, P., M. CASTONGUAY, D. D'AMOURS, P. MAGNAN, 1992. Growth comparison between juvenile Atlantic mackerel (Scomber scombrus) from the two spawning groups of the Northwest Atlantic. Can. J. Fish. Aquat. Sci., 49: 2242-2248 .

HODSON, P.V., C. DESJARDINS, É. PELLETIER, M. CASTONGUAY, R. McLEOD, C.M. COUILLARD, 1992. Baisse de la pollution chimique des anguilles d'Amérique (Anguilla rostrata) capturées dans l'estuaire du Saint-Laurent. Rapp. tech. can. sci. halieut. aquat., 1876, 60 p .

Click to see all the text

American eels, Anguilla rostrata, are catadromous, and grow to maturity in Lake Ontario and in tributaries to the St. Lawrence River. Concern for mass mortalities of adult eels, high levels of chemical contamination, and a recent decline of recruitment prompted a study of the role of contaminants in the health of eels, the role of eels as vectors of contaminants to Beluga whales (Delphinapterus leucas) and the changes in contamination since an earlier large scale survey in 1982. Mercury, PCB, mirex and pesticide levels were measured in migratory adult eels in Kamouraska, Québec. Similar analyses were conducted on two eel samples from fishermen in Cacouna and Saint-Irénée, and on a control eel sample from a small tributary of the north shore of the St. Lawrence Estuary. Dioxins, furans and PAH concentrations were also determined on a small number of fish. Results indicate that eels from the upper St. Lawrence River/Lake Ontario were much more contaminated with PCBs, mirex and pesticides than the control population; concentrations did not vary among sites on the St. Lawrence River. Levels of PCBs and mirex have declined by 68 and 56 % respectively since 1982. Only 36 % of eels analyzed exceeded the guidelines for PCBs in fish, compared to 80 % in 1982; for mirex, the percentage declined from 52 % in 1982 to 29 % in 1990. Levels of PCBs, mirex and pesticides varied among weeks with a slight trend of increasing concentrations towards the end of the migration. Concentrations of PAH, dioxins and furans were usually less than their detection limits, and well below any guidelines. These results suggest that the risk of organic chemical toxicity to Belugas from consuming eels is declining from year to year. Mercury levels were constant among sites and times, indicating that accumulation originates mostly from natural sources or atmospheric deposition.

CASTONGUAY, M., P. SIMARD, P. GAGNON, 1991. Usefulness of Fourier analysis of otolith shape for Atlantic mackerel (Scomber scombrus) stock discrimination. Can. J. Fish. Aquat. Sci., 48: 296-302 .

THERRIAULT, J.-C., J. PAINCHAUD, P. HODSON, M. CASTONGUAY, G. WALSH, J. GEARING, M. KINGSLEY, B. TESSIER, 1990. Le plan d'action Saint-Laurent à la Direction des sciences, Institut Maurice-Lamontagne : orientations et objectifs. Rapp. manus. can. sci. halieut. aquat., 2055, 15 p .

Click to see all the text

The authors from the Maurice Lamontagne Institute, Quebec, Canada, present a research plan that will add to their knowledge of the causes and effects of the chemical pollution of the St. Lawrence River.

CASTONGUAY, M., J.-D. DUTIL, C. DESJARDINS, 1990. Distinction entre des anguilles d'Amérique (Anguilla rostrata) d'origines géographiques différentes basée sur leur teneur en contaminants organochlorés. Pages 603-614 in D. Messier, P. Legendre & C.E. Delisle (éd.). Symposium sur le Saint-Laurent : un fleuve à reconquérir. Association des biologistes du Québec et Centre Saint-Laurent (Collection environnement et géologie, 11) .

CASTONGUAY, M., J.-D. DUTIL, C. AUDET, R. MILLER, 1990. Locomotor activity and concentration of thyroid hormones in migratory and sedentary juvenile American eels. Trans. Am. Fish. Soc., 119: 946-956 .

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.

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.

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 .

CASTONGUAY, M., J.-D. DUTIL, C. DESJARDINS, 1989. Distinction between American eels (Anguilla rostrata) of different geographic origins on the basis of their organochlorine contaminant levels. Can. J. Fish. Aquat. Sci., 46: 836-843 .

CASTONGUAY, M., B. MERCILLE, 1988. Le maquereau bleu (Scomber scombrus Linné) du nord-ouest de l'Atlantique, sous-régions 2 à 6 de l'OPANO : évaluation du stock en 1987. CSCPCA doc. rech., 88/50, 34 p .

CASTONGUAY, M., J. LANDRY, 1987. Le maquereau bleu (Scomber scombrus Linné) du nord-ouest de l'Atlantique, sous-régions 2 à 6 de l'OPANO. CSCPCA doc. rech., 87/47, 34 p .

MAGUIRE, J.-J., Y.C. CHAGNON, M. CASTONGUAY, B. MERCILLE, 1987. A review of mackerel management areas in the Northwest Atlantic. CAFSAC Res. Doc., 87/71, 31 p .

The history of the stock unit presently used for management of Northwest Atlantic mackerel is reviewed. Although two spawning populations were known to exist, the management area was defined on the basis of mixing of the two populations on overwintering grounds where most of the fishery was then occurring. The biological basis for the definition of the management unit is reviewed and shows that tagging data were the main factor in defining the management area. Recent genetic analyses do not suggest modifying the currently used management area.