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

LACHANCE, A.-A., R. HENNEBICQ, B. MYRAND, J.-M. SÉVIGNY, E. KRAFFE, Y. MARTY, I. MARCOTTE, R. TREMBLAY, 2011. Biochemical and genetic characteristics of suspension-cultured mussels (Mytilus edulis) in relation to byssal thread production and losses by fall-off. Aquat. Living Resour., 24(3): 283-293 .

Mussel culture relies on the mussel self-attachment capacity through byssus production. By doing so, no cages or containment devices are needed. It has been previously suggested that thread production requires a nonnegligible part of the energy expenditure in blue mussels Mytilus edulis. Therefore our work investigates the relationships between byssal thread production, mussels energetic reserves and phospholipids profiles in the foot. The relationship between thread production and heterozygosity was also examined. The study was realized in a small lagoon of the Îles-de-la-Madeleine, southern Gulf of St. Lawrence, Canada, on four sampling dates between June and September encompassing the pre- to post-spawning periods. Our results show a significant relationship between the thread numbers and attachment strength. However, no correlations were found between energy reserves, phospholipids composition of the foot or heterozygosity level and byssal production. Our results suggest that mussels in suspension culture in this lagoon were not energy-limited so that the energy reserves did not influence the byssal thread production.©2011 EDP Sciences, IFREMER, IRD

SÉVIGNY, J.-M., A. VALENTIN, A. TALBOT, N. MÉNARD, 2009. Connectivité entre les populations du fjord du Saguenay et celles du golfe du Saint-Laurent;Connectivity between Saguenay Fjord populations and those of the Gulf of St. Lawrence. Rev. Sci. Eau;J. Water Sci., 22(2): 315-339 .

Microsatellite and allozyme analyses on various species of bottom fishes (cod, Greenland halibut and redfish) and crustace ans (snow crab, northern shrimp) show that individuals from the Saguenay Fjord and from the St. Lawrence belong ta the same populations. The only genetic difference observed is at the Pan I locus of cod. This differentiation may be caused by selection that would act in the Saguenay Fjord, rather than due to the genetic isolation of the population. Complementary data available for bottom fish (elemental composition of otoliths, body morphometry, and para ice fauna) show clear differences between the aguenay and the St. Lawrence. These differences suggest residence of individuals in the Saguenay and the St. Lawrence for a large proportion of their life cycle. Considering the low larval survival observed in the fjord, this review Suggests that the bottom fish populations from the Saguenay represent sink populations whose recruitment depends largely or solely on migration of juvenile from the St. Lawrence. Although there are no complememary data for crustacean species, it is possible that migration and residence are processes operating for those species as well.©2009 RSE inc.

MYRAND, B., R. TREMBLAY, J.-M. SÉVIGNY, 2009. Decreases in multi-locus heterozygosity in suspension-cultured mussels (Mytilus edulis) through loss of the more heterozygous individuals. Aquaculture, 295: 188-194 .

The mean multi-locus heterozygosity (MLH) of suspension-cultured mussels has been reported to decrease within a few months after traditional sleeving in previous studies. Two experiments were carried out to determine if this decrease could be attributed to the more rapid migration of the more heterozygous mussels out of the mesh tubes after sleeving. Since these individuals occur in greater numbers at the periphery of the sleeves, they are more susceptible to fall-offs. In the first experiment, the mean MLH of the mussels emerging from the mesh tubes was significantly higher than the MLH of the spat used for sleeving two weeks before. In a second experiment with caged and free sleeves under field conditions, a significant decrease in MLH was observed, but only for the mussels from the free sleeves. This decrease occurred in late December, only one month after sleeving. It is hypothesized that the experimental cages limited turbulence and thus fall-offs during the weeks following sleeving. As a consequence, the slower moving homozygotes were able to catch up with the faster heterozygotes at the sleeve's periphery. In contrast, mussels in the free sleeves may have experienced more turbulent conditions leading to high fall-offs of the more heterozygous mussels at the sleeve's periphery during the crucial period following sleeving. These losses could impact mussel production since MLH explained 32 % of the variation in individual dry tissue weight in this study. Furthermore, the total fresh weight of mussels with high MLH (5–7 heterozygous loci) was almost twice that of the mussels with low MLH (0–2 heterozygous loci) about one year after sleeving: 11.38 vs. 5.95 g. In addition, there were 3.7 times more commercial-sized mussels (N50 mm) with a high MLH than with a low MLH (80 % vs. 21.5 %). In contrast to traditional sleeving with plastic mesh tubes, a new method of mechanical sleeving provides continuous sleeves wrapped in cotton cloth. This biodegradable cloth helps retain the heterozygotes on the sleeves before it disintegrates.©2009 Elsevier B.V.

PELLETIER, É, J.-M. SÉVIGNY (éd.), 2009. Parc marin Saguenay-Saint-Laurent : dix années de recherche et de conservation. Revue des Sciences de l'eau (Rev. Sci. Eau ; J. Water Sci.), 22(2) .

MYRAND, B., R. TREMBLAY, J.-M. SÉVIGNY, 2009. Impact of suspension culture using mesh sleeves on genetic characteristics of Mytilus edulis L. in Canada. Aquaculture, 291(3-4): 147-153 .

Previous studies have suggested that a large proportion of the more heterozygous mussels are lost while in suspension culture. Such a reduction in multi-locus heterozygosity (MLH) could impact mussel production because more heterozygous individuals have better growth and survival than more homozygous ones. The present study followed the changes in MLH over a year in two different cohorts and found a reduction in MLH during the culture cycle for both cohorts. This reduction did not occur during the early phases of the culture operations, such as sleeving (= socking), or during the first weeks in suspension culture, but took place during the following growing season starting in early summer for both cohorts. The MLH decrease was not associated with different environmental conditions at the growing site. It is hypothesized that mussels characterized by high MLH are more mobile than those with lower MLH and migrate out of the mesh tubes faster after sleeving to get access to better growing conditions (space and food). However, being at the periphery of the sleeves, these more heterozygous individuals are more vulnerable to fall-offs due to turbulence and/or self-thinning. We suggest that the MLH decrease on the sleeves is not caused by the selective mortality of more heterozygous individuals but rather by higher losses through fall-offs.©2009 Elsevier B.V.

MEDINA, A., J.-C. BRÊTHES, J.-M. SÉVIGNY, 2008. Habitat fragmentation and body-shape variation of African hind Cephalopholis taeniops (Valenciennes) in an archipelago system (Cape Verde, eastern Atlantic Ocean). J. Fish Biol., 73(4): 902-925 .

Morphological variations of the serranid fish Cephalopholis taeniops were studied in relation to habitat fragmentation in the Cape Verde Archipelago. While a significant allometric effect existed (11.5 % of total body-shape variation), differences in morphology associated with sex and ontogeny were not significant. MANOVA followed by CVA showed that each island presented a particular allometric pattern. Average body shape for all islands was well discriminated with CVA models. Pair-wise comparisons of the ontogeny of morphological change between islands revealed that northern islands (Santo Antão, São Vicente and Santa Luzia) along with Boavista Island showed a similar direction in shape ontogeny, while all other paired comparisons indicated different ontogenetic patterns. When comparing directions of inter-population shape changes, individuals from Fogo Island, the southernmost locality, departed far from the orthogonal relation, suggesting that they were undergoing independent body-shape trajectories. Physical isolation by geographic distance and depth was positively correlated with morphological divergence among populations from different islands. This finding supports the hypothesis that habitat fragmentation in the Cape Verde Archipelago can be interpreted in terms of marine population structure.© 2008 The Authors Journal compilation ©2008 The Fisheries Society of the British Isles

PUEBLA, O., J.-M. SÉVIGNY, B. SAINTE-MARIE, J.-C. BRÊTHES, A. BURMEISTER, E.G. DAWE, M. MORIYASU, 2008. Population genetic structure of the snow crab (Chionoecetes opilio) at the Northwest Atlantic scale. Can. J. Fish. Aquat. Sci., 65: 425-436 .

Marine species with planktonic larval durations of several months (teleplanic larvae) can potentially maintain demographic connectivity across large geographical distances. This perspective has important fundamental and applied implications, notably for the understanding of evolutionary and ecological processes in the marine realm, the implementation of marine protected areas, and fisheries management. Here we present, at the scale of the Northwest Atlantic, a spatial analysis of snow crab (Chionoecetes opilio, Majoidea) population genetic structure, a species that has a planktonic larval phase of 3 to 5 months. Eight microsatellite markers analysed on 847 C. opilio samples from 13 locations revealed an absence of significant genetic structure along the west coast of Greenland and within Atlantic Canada from southern Labrador to Nova Scotia. These results are consistent with a scenario of extensive demographic connectivity among C. opilio populations and have implications for the management of this species, which supports one of the most important Canadian and Greenlandic fisheries in terms of economic value. A genetic break is nevertheless identified between Greenland and Atlantic Canada, showing that genetic structure can develop within seas (the Labrador Sea in this case) despite the occurrence of very long planktonic larval stages.©2008 NRC Canada

SAINTE-MARIE, B., T. GOSSELIN, T., J.-M. SÉVIGNY, N. URBANI, 2008. The snow crab mating system: opportunity for natural and unnatural selection in a changing environment. Bull. Mar. Sci., 83(1): 131-161 .

The impact of fishing as a driver of sexual selection is not well understood in crustaceans. Fishing must be viewed as acting in conjunction with, or in opposition to, natural factors, which also modify the context for sexual competition, mate choice, and sexual conflict. We review knowledge of the polygynandrous mating system of the snow crab and evaluate the likely interplay between natural and fishing forces in the process of sexual selection. The snow crab has determinate growth and two female reproductive stages (primiparous and multiparous) with discrete and disjunct mating seasons. Temperature shifts the spectrum of size at maturity in both sexes and determines female reproductive tempo, thereby altering sperm supply, egg production, and operational sex ratio. Population dynamics modulates the phenotype of receptive individuals and the direction and intensity of sexual competition over time. Fishing directed only at large males may attenuate or exacerbate some aspects of sexual conflict at primiparous mating, depending on the natural context, but otherwise it consistently promotes mating of less fecund males, reduces opportunity for female mate choice, and increases the likelihood of sperm limitation. These changes have mixed but still incompletely appreciated effects on female reproductive fitness. The long-term potential for selection against large size at maturity remains uncertain. ©2008 Rosenstiel School of Marine and Atmospheric Science of the University of Miami

DE LAFONTAINE, Y., J.-M. SÉVIGNY, R. CALVÉ, G. VERREAULT, S.-P. DESPATIE, É. VEILLEUX, 2008. Chinese mitten crabs (Eriocheir sinensis) in the St. Lawrence River and Estuary, Canada: new records and risk of invasion. Aquat. Invasions, 3(2): 153-163 .

Recent reports of Chinese mitten crabs (Eriocheir sinensis) in the St. Lawrence River and Estuary were compiled to assess the possible sources of the species based on genetic analyses and data on shipping traffic. Between 2004 and 2007, nine specimens were captured in both the fresh and estuarine waters of the St. Lawrence; a number unprecedented in the 40 years since the mitten crab was first sighted in the Great Lakes-St. Lawrence Basin. These sightings, added to those of the eastern United States, are indicative of a large-scale wave of introduction of the mitten crab to Eastern North America. Genetic analyses have suggested that the S1. Lawrence specimens likely originated in Europe. No significant changes have been noted in maritime traffic to the St. Lawrence in recent years, but analyses have revealed that 42 % of ships came from European countries where established populations of Chinese mitten crab have exhibited recent bursts in abundance. It is suggested that the recent wave of introduction of mitten crabs to Eastern North America is related more to changes in the abundance of European populations than to changes in shipping vector activity. These recent sightings are of major concern with regard to the establishment and spread of the species. It is therefore recommended that long-term monitoring programs be set up immediately to track the progress of the mitten crab invasion in the St. Lawrence River basin.©2008 European Research Network on Aquatic Invasive Species

SÉVIGNY, J.-M., 2008. Advice on the stock definition of redfish (Sebastes fasciatus and S. mentella) in units 1 and 2. DFO, Canadian Science Advisory Secretariat, Science Advisory Report, 2008/026, 12 p .

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SÉVIGNY, J.-M., 2008. Avis sur la définition des stocks de sébastes (Sebastes fasciatus et S. mentella) des unités 1 et 2. MPO, Secrétariat canadien de consultation scientifique, Avis scientifique, 2008/026, 13 p .

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PERNET, F., R. TREMBLAY, I. REDJAH, J.-M. SÉVIGNY, C. GIONET, 2008. Physiological and biochemical traits correlate with differences in growth rate and temperature adaptation among groups of the eastern oyster Crassostrea virginica. J. Exp. Biol., 211(6): 969-977 .

We tested two hypotheses in this study: first, that intraspecific growth variations in a marine bivalve are correlated with physiological (basal metabolic rate and scope for growth) and biochemical (membrane lipids) characteristics, and, second, that this bivalve shows intraspecific variations in physiological and biochemical adaptations to temperature. To test these hypotheses, five genetically distinct groups of juvenile oysters Crassostrea virginica that showed differences in their growth rates were maintained in the laboratory (1) for further measurements of growth and standard metabolic rates and (2) subjected to acclimation at 4 °C, 12 °C and 20 °C and further examined for scope for growth and determination of membrane lipid composition. Our results show that a lower basal metabolic rate and lower unsaturation index of membrane lipids coincides with higher growth rates and a higher scope for growth in oysters. We provide evidence that intraspecific differences in basal metabolic rate in oysters are related to membrane unsaturation as predicted by Hulbert's theory of membranes as metabolic pacemakers. Furthermore, our results suggest that the theory of membranes as metabolic pacemakers is related to intraspecific differences in growth. A perfect negative relationship was observed between the acclimation temperature and the unsaturation index of membrane lipids in oysters, as predicted by the homeoviscous adaptation theory. However, changes in the unsaturation index in response to temperature were mainly due to variations in the eicosapentaenoic (20:5n-3) fatty acid in fast-growing oysters, whereas slow-growing animals changed both docosahexaenoic acid (22:6n-3) and 20:5n-3. Thus, the pattern of biochemical compensation in response to temperature in this species shows intraspecific variation.

VALENTIN A.E., X. PENIN, J.-P. CHANUT, J.-M. SÉVIGNY, F. J. ROHLF, 2008. Arching effect on fish body shape in geometric morphometric studies. J. Fish Biol., 73: 623-638 .

Upward and downward arching of the body was observed during a study on redfishes Sebastes sp. Population structure in the north-west Atlantic Ocean. The present study investigated the potential causes of this arching artefact. The results suggested that it is not related to biological factors (size or species) or to the preservation technique (freezing), but is rather due to slight posture differences between fishes during landmark capture. The consequences of the arching artefact on data analysis are discussed. An approach coupling a PCA-based model of the arching with Burnaby's orthogonal projection is proposed for removing the artefact from the data.©2008 The Authors & The Fisheries Society of the British Isles

TREMBLAY, I., M. FRÉCHETTE, J.-M. SÉVIGNY, H. E. GUDERLEY, 2007. Are bioenergetic properties linked with shell fluctuating asymmetry and heterozygosity in Iceland scallop, Chlamys islandica?. J. Shellfish Res., 26(1): 17-23 .

We investigated the relationship between physiological properties, swimming performance, shell fluctuating asymmetry, and heterozygosity at allozyme loci in the Iceland scallop, Chlamys islandica, in an attempt to describe potential physiological mechanisms for the negative relationship between shell fluctuating asymmetry and survival of this species in pearl nets (Fréchette & Daigle 2002). No clear relationship was observed between shell fluctuating asymmetry and the different physiological and genetic parameters, although the maximum number of contractions in a series during escape tests and the specific activity of arginine kinase in the adductor muscle were linked with shell asymmetry before the application of corrections for multiple comparisons. Pyruvate kinase activity in soft tissues was higher in animals that were heterozygous at 2 loci compared with those that were heterozygous at 4 loci. Although our exploratory study suggests that shell asymmetry may reflect bioenergetic difficulties, further study is required to confirm such links. ©2007 National Shellfisheries Association

SÉVIGNY, J.-M., R. MÉTHOT, H. BOURDAGES, D. POWER, P. COMEAU, 2007. Review of the structure, the abundance and distribution of Sebastes mentella and S. fasciatus in Atlantic Canada in a species-at-risk context: an update ; Revue de la structure, de l’abondance et de la distribution de Sebastes mentella et S. fasciatus dans le Canada atlantique dans le contexte des espèces en péril : mise à jour. DFO, Canadian Science Advisory Secretariat, Research Document ; MPO, Secrétariat canadien de consultation scientifique, Document de recherche, 2007/085, 109 p .

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This document presents the information reviewed and analyzed by Fisheries and Oceans (DFO) that can be used by the Committee on Status of Endangered Wildlife in Canada (COSEWIC) in assessing status and extinction risk of the two main redfish species (Sebastes fasciatus and S. mentella) in the Northwest Atlantic. Redfish population structure was evaluated in the context of Evolutionarily Significant Units (ESU). The review did not provide evidence of the existence of ESUs within current management units. Therefore, all the analyses were carried out on the actual unit stocks. Methods developed to separate redfish by genotype (for Unit 1-3) or meristics (for NAFO Divisions 2GHJ3KLMNO) were applied to the research vessel survey data to obtain abundance indices. Three distribution indices were calculated: the area of occupancy, the minimum area occupied by 95 % of the stock, and the Gini index of aggregation. No general pattern or trend in geographic distribution was evident. The Unit 1 stock experienced a substantial decline at the beginning of the 1990 and has not recovered yet. However, a new year-class (2003), which seems to be quite important, was observed since the 2005 survey. The stock in NAFO Divisions 2GHJ 3K experienced declines but has shown some signs of recovery. The redfish stocks in remaining management units have not shown signs of decline or the information available for these stocks may not reflect the abundance. Fishery and/or the lack of recruitment were considered the main causes of abundance decline for the stocks in Unit 1 and in NAFO Div. 2GHJ 3K. However, environmental changes and elevated natural mortality were also identified as possible causes of decline. Mature population abundance indices of all redfish stocks in Atlantic Canada are at from one to three orders of magnitude greater than the COSEWIC threshold of 10 000 mature individuals.

MEDINA, A., J.-C. BRÊTHES, J.-M. SÉVIGNY, B. ZAKARDJIAN, 2007. How geographic distance and depth drive ecological variability and isolation of demersal fish communities in an archipelago system (Cape Verde, Eastern Atlantic Ocean). Mar. Ecol., 28(3): 404-417 .

Cape Verde is a tropical oceanic ecosystem, highly fragmented and dispersed, with islands physically isolated by distance and depth. To understand how isolation affects the ecological variability in this archipelago, we conducted a research project on the community structure of the 18 commercially most important demersal fishes. An index of ecological distance based on species relative dominance (D_i) is developed from Catch Per Unit Effort, derived from an extensive database of artisanal fisheries. Two ecological measures of distance between islands are calculated: at the species level, ΔD_i, and at the community level, ΔD (sum of ΔD_i). A physical isolation factor (I_db) combining distance (d) and bathymetry (b) is proposed. Covariance analysis shows that isolation factor is positively correlated with both ΔD_i and ΔD, suggesting that I_db can be considered as an ecological isolation factor. The effect of I_db varies with season and species. This effect is stronger in summer (May to November), than in winter (December to April), which appears to be more unstable. Species react differently to Idb, independently of season. A principal component analysis on the monthly (ΔD_i) for the 12 islands and the 18 species, complemented by an agglomerative hierarchical clustering, shows a geographic pattern of island organization, according to I_db. Results indicate that the ecological structure of demersal fish communities of Cape Verde archipelago, both in time and space, can be explained by a geographic isolation factor. The analytical approach used here is promising and could be tested in other archipelago systems.©2007 Blackwell Publishing Ltd.

GOSSELIN, T., B. SAINTE-MARIE, J.-M. SÉVIGNY, 2007. Individual identification of decapod crustaceans II : natural and genetic markers in snow crab (Chionoecetes opilio). J. Crust. Biol., 27(3) : 399-403 .

Methods for the identification of individual crustaceans are needed in many types of studies. Snow crab (Chionoecetes opilio) individuals have distinctive natural patterns of tubercles and spines on the carapace. The results of a double-marking experiment using these natural markers along with genetic (microsatellite) markers confirm that natural markings are a reliable means of recognizing individuals within groups of tens to hundreds of snow crabs. These natural markings are persistent through at least two molts. They have already demonstrated their usefulness in laboratory studies of molting and mating and could be applied to a wider spectrum of investigations. A cursory examination suggests that similar carapace features could be used to identify individuals in other crustacean species as well.©2007 The Crustacean Society

CAMPANA, S. E., A. VALENTIN, J.-M. SÉVIGNY, D. POWER, 2007. Tracking seasonal migrations of redfish (Sebastes spp.) in and around the Gulf of St. Lawrence using otolith elemental fingerprints. Can. J. Fish. Aquat. Sci., 64: 6-18 .

Large concentrations of beaked redfish (Sebastes mentella and Sebastes fasciatus) overwinter in the Cabot Strait and the approaches of the Gulf of St. Lawrence each year. Synoptic research vessel surveys indicate that redfish are distributed more widely in the summer than in the winter, particularly within the Gulf. Significant differences in the trace element composition of the otolith ("otolith elemental fingerprint") were observed among summer aggregations, indicating that the aggregations maintained some degree of separation while in the Gulf. Sebastes mentella and S. fasciatus were readily distinguished based on otolith elemental fingerprints. Using the elemental fingerprints of the summer samples as a natural tag, we found that S. mentella tended to move out of the Gulf in the winter. Aggregations of S. mentella found in the east during the summer were not found in our winter collections. The elemental fingerprints of S. mentella from the Saguenay Fjord were clearly distinct from redfish further east in the Gulf of St. Lawrence, indicating that this group had been separated from other redfish for much of their life. The implications of our findings extend not only to the fisheries management of redfish, but also to the extent of movement expected of deepwater fish species.

VALENTIN, A., J.-M. SÉVIGNY, B. MORIN, D. POWER, R.M. BRANTON, 2006. Extensive sampling and concomitant use of meristic characteristics and variation at the MDH-A* locus reveal new information on redfish species distribution and spatial pattern of introgressive hybridization in the Northwest Atlantic. J. Northwest Atl. Fish. Sci., 36: 65-80 .

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Variability at theMDH-A* locus, of anal fin ray number and extrinsic gasbladder muscle pattern is used to describe the distribution of Sebastes fasciatus and S. mentella in the Northwest Atlantic and to define the geographical boundaries of the area of introgressive hybridization between the two species. Sebastes mentella distribution extends from the Gulf of St. Lawrence northward while S. fasciatus is distributed from the southern Grand Banks southward as described in earlier studies. Sebastes fasciatus is also found in the southern Labrador Sea where the species appears to reach its northernmost limit. The distribution of the two species overlaps mainly in the Gulf of St. Lawrence and the Laurentian Channel, around the Grand Banks and on Flemish Cap. This area of sympatry comprises a smaller area where heterozygous individuals at the MDH-A* locus are observed and where introgressive hybridization occurs. This area is mostly restricted to the Gulf of St. Lawrence and the Laurentian Channel. The west-east gradient in the abundance of introgressed individuals suggests that the Gulf of St. Lawrence is the centre of introgressive hybridization and that larval dispersion or migration of juveniles and adults takes place from the Gulf of St. Lawrence towards south Newfoundland and the Grand Banks. In contrast, the absence of heterozygous individuals at the MDH-A* locus outside the Gulf of St. Lawrence and the Laurentian Channel indicates that the dispersion of these individuals is limited for all stages of the life cycle.

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

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

LANDRY T., M. SKINNER, A. LEBLANC, D. BOURQUE, C.W. McKINDSEY, R. TREMBLAY, P. ARCHAMBAULT, L. COMEAU, S. COURTENAY, F. HARTOG, M. OUELLETTE, J.-M. SÉVIGNY, 2006. A scientific review of bivalve aquaculture : interaction between wild and cultured species. Pages 80-138 in A scientific review of the potential environmental effects of aquaculture in aquatic ecosystems. Dept. of Fisheries and Oceans (Can. Tech. Rep. Fish. Aquat. Sci., 2450(5)) .

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This paper reviews the present state of knowledge on interactions between wild and cultured species within the context of bivalve mariculture in Canada. It also identifies critical knowledge gaps and recommends research to address these gaps. The literature reviewed includes national and international information covering bivalve aquaculture, bivalve restoration, coastal community and ecology. This review is focused on changes affecting the pelagic community, benthic communities, predator species, genetic structures, and the risk of introducing invasive species.

VALENTIN, A., J.-P. CHANUT, X. PENIN, J.-M. SÉVIGNY, 2005. Analyse conjointe de données génétiques et morphométriques : rapprocher les distances. 4 pages in Actes des XXXVIIèmes Journées de Statistique, Pau, France, 6-10 juin 2005 .

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

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

LAMBREY DE SOUZA, J., J.-M. SÉVIGNY, J.-P. CHANUT, 2004. Caractérisation génétique du maquereau bleu (scomber scombrus) dans l'Atlantique nord-est. 6 pages in Actes des XXXVIèmes Journées de statistique .

The left branch of the mitochondrial DNA (mtDNA) control region was sequenced on 75 Atlantic mackerel (Scomber scombrus) sampled in the Gulf of ST. Lawrence, the Gulf of Maine and off the North Carolina coast in an attempt to determine if the northern and southern populations of this species are genetically differentiated. The variability of the mtDNA control region is very high in this species. Indeed, 48 haplotypes were observed in the 75 individuals and haplotype diversity values varied between 0,982 in the Gulf of Maine to 0.992 in the Gulf of St. Lawrence. The result of the analysis of molecular variance (AMOVA) did not reveal significant difference between the northern and the southern populations and are in agreement with those of the phylogenetic analysis, which did not reveal grouping of individuals according to their geographic origin. The results of the present study suggest that, if homing is a feature of the reproductive behaviour of the Atlantic mackerel, straying appears to be sufficiently important to prevent genetic divergence of the two populations in the Northwest Atlantic. However, the very high variability of the selected mtDNA fragment together with the low sample size may have prevented the detection of population structure.

MORIN, B., R. METHOT, J.-M. SEVIGNY, D. POWER, B. BRANTON, T. McINTYRE, 2004. Review of the structure, the abundance and distribution of Sebastes mentella and S. fasciatus in Atlantic Canada in a species-at-risk context ; Revue de la structure, de l’abondance et de la répartition de Sebastes mentella et S. fasciatus dans le Canada atlantique dans le contexte des espèces en péril. DFO, Canadian Science Advisory Secretariat, Research Document ; MPO, Secrétariat canadien de consultation scientifique, Document de recherche, 2004/058, 96 p .

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This document presents the information reviewed and analyzed by Fisheries and Oceans (DFO) that could be used by the Committee on Status of Endangered Wildlife in Canada (COSEWIC) in assessing status and extinction risk of the two main species of redfish (Sebastes fasciatus and S. mentella) in the Northwest Atlantic. Redfish population structure was evaluated in the context of “evolutionarily significant units”. The review did not provide evidence to indicate the existence of ESUs within current management units, therefore all the analyses were realized on the current unit stocks. Methods have been developed to separate redfish by genotype and applied to the research vessel (RV) survey data to obtain abundance indices. Three distribution indices were calculated: the area of occupancy, the minimum area occupied by 95 % of the stock, and the Gini index of aggregation. No general pattern or trend in geographic distribution was evident. One stock experienced a substantial decline and had not recovered (Unit 1). One stock experienced declines but has shown some recovery (NAFO divisions 2GHJ 3K). The remaining management units have not shown a decline or the information available may not reflect the abundance. Fishery exploitation and the lack of recruitment were considered the main causes of abundance decline for two stocks (Unit 1 and 2GHJ 3K), although environmental changes and elevated natural mortality were identified as possible factors. Mature population abundance indices of all redfish stocks in Atlantic Canada are at least two orders of magnitude greater than the COSEWIC threshold of 10 000 mature individuals.

PUEBLA, O., É. PARENT, J.-M. SÉVIGNY, 2003. New microsatellite markers for the snow crab Chionoecetes opilio (Brachyura: Majidae). Mol. Ecol. Notes, 3(4), p. 644 .

VALENTIN, A., J.-P. CHANUT, X. PENIN, J.-M. SEVIGNY, 2003. Morphométrie du sébaste. Modélisation et correction d'une déformation indésirable. Pages 863-866 in Actes des XXXVèmes Journées de statistique .

MARCOGLIESE, D.J., E. ALBERT, P. GAGNON, J.-M. SÉVIGNY, 2003. Use of parasites in stock identification of the deepwater redfish (Sebastes mentella) in the Northwest Atlantic. Fish. Bull. 101: 183-188 .

ROQUES, S., J.-M. SÉVIGNY, L. BERNATCHEZ, 2002. Genetic structure of deep-water redfish, Sebastes mentella, populations across the North Atlantic. Mar. Biol., 140: 297-307 .

MYRAND, B., R. TREMBLAY, J.-M. SÉVIGNY, 2002. Selection Against Blue Mussels (Mytilus edulis L.) Homozygotes Under Various Stressful Conditions. J. Hered., 93(4): 238-248 .

SAINTE-MARIE, B., J.-M. SÉVIGNY, M. CARPENTIER, 2002. Interannual variability of sperm reserves and fecundity of primiparous females of the snow crab (Chionoecetes opilio) in relation to sex ratio. Can. J. Fish. Aquat. Sci., 59: 1932-1940 .

Demographics of adults and reproductive condition of primiparous (first brood) females of the snow crab (Chionoecetes opilio) were monitored annually from 1994 to 2002 at a fished site to investigate the possibility that sperm supply limits embryo production. Abundance of primipara fluctuated 533-fold because of a recruitment pulse, and this caused a large oscillation in the sex ratio of adult males to primipara. Annual mean of stored ejaculate weight (SL) and potential fecundity index (PF, clutch weight x percent fertilized eggs) adjusted to constant primipara carapace width ranged from 31 to 130 mg by spermatheca and from 1.97 to 3.43 g by clutch, respectively. Annual mean of SL and number of stored sperm (range 3.81 x 10⁶ to 35.00 x 10⁶ sperm by spermatheca) decreased when sex ratio decreased, probably because of a combined reduction of sperm allocation and female promiscuity. Annual mean PF was negatively correlated with abundance of small males, which may reflect egg losses during postoviposition matings. Althoug sociosexual context has a large impact on reproductive condition of primipara, the possibility that sperm supply limits embryo production could not be confirmed or excluded because of the complexity of snow crab mating behavior.

VALENTIN, A., J.-M. SÉVIGNY, J.-P. CHANUT, 2002. Geometric morphometrics reveals body shape differences between sympatric redfish Sebastes mentella, Sebastes fasciatus and their hybrids in the Gulf of St. Lawrence. J. Fish Biol., 60: 857-875 .

VALENTIN, A., J.-P. CHANUT, J.-M. SÉVIGNY, 2001. Point de concordance et de différenciation dans la morphologie du sébaste. Pages 692-696 in Actes des XXXIIIèmes Journées de statistique .

TREMBLAY, r., B. MYRAND, J.-M. SÉVIGNY, 2001. Impacts of aquaculture practices on genetic variability of blue mussels (Mytilus edulis). Bull. Aquac. Assoc. Can., 101(2): 11-14 .

ROQUES, S., J.-M. SEVIGNY, L. BERNATCHEZ, 2001. Evidence for broadscale introgressive hybridization between two redfish (genus Sebastes) in the North-west Atlantic : a rare marine example. Mol. Ecol., 10:149-165 .

SÉVIGNY, J.-M., L. SAVARD, D.G. PARSONS, 2000. Genetic characterization of the northern shrimp, Pandalus borealis, in the Northwest Atlantic using electrophoresis of enzymes. J. Northwest Atl. Fish. Sci., 27: 161-175 .

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SAINTE-MARIE, G., B. SAINTE-MARIE, J.M. SEVIGNY, 2000. Ejaculate-storage patterns and the site of fertilization in female snow crabs (Chionoecetes opilio; Brachyura, Majidae). Can. J. Zool., 78: 1902-1917 .

A light-microscopy study of mated female snow crabs (Chionoecetes opilio) was conducted to investigate the site of fertilization and to resolve how multiple ejaculates are stored in the spermathecae. In its basic configuration, an ejaculate consisted of a layer or patch of spermatophores enclosing mature spermatids that was capped by a relatively large volume of amorphous matter, which in turn could include a patch of spermatophores containing immature spermatids. Up to 10-12 ejaculates were stored in the spermathecae with the largest loads. An ejaculate was initially deposited in the intermediate chamber and ventral part of the spermatheca, and was displaced toward the dorsal part of the spermatheca when a new ejaculate was inserted. Ejaculates were neatly stratified along the ventrodorsal axis of spermathecae with small to moderate loads, but they were disrupted and the storage pattern was disorderly in spermathecae with large loads. Ejaculate stratification favors last-male sperm precedence and single-male paternity. However, multiple-male paternity might occur in females with large spermathecal loads, in part because several ejaculates can co-occur close to the oviduct opening. Mixing of male and female gametes in preparation for oviposition, and probably also fertilization, occurs to some° in the ovaries©2000 National Research Council Canada

SÉVIGNY, J.-M., P. GAGNÉ, Y. de LAFONTAINE, J. DOBSON, 2000. Identification and distribution of larvae of redfish (Sebastes fasciatus and S. mentella : Scorpaenidae) in the Gulf of St. Lawrence. Fish. Bull., 98: 375-388 .

ROQUES, S., J.-M. SÉVIGNY, L. BERNATCHEZ, D. POWER, 2000. Redfish species distribution and population genetic structure in the Northwest Atlantic: preliminary results. NAFO SCR Doc., 00/48, 17 p .

MYRAND, B., R. TREMBLAY, J.-M. SÉVIGNY, H. GUDERLEY, J.H. HIMMELMAN, 1999. What did we learn about summer mortality of suspension-cultured mussels in the Magdalen Islands, Quebec?. Bull. Aquac. Assoc. Can., 99(2): 9-13 .

KIRCHHOFF, S., J.-M. SÉVIGNY, C.M. COUILLARD, 1999. Genetic and meristic variations in the mummichog Fundulus heteroclitus, living in polluted and reference estuaries. Mar. Environ. Res., 47: 261-283 .

DESROSIERS, B., J.-M. SÉVIGNY, J.-P. CHANUT, 1999. Restriction fragment length polymorphism of rDNA in the redfishes Sebastes fasciatus and S. mentella (Scorpaenidae) from the Gulf of St. Lawrence. Can. J. Zool., 77: 267-277 .

A restriction fragment length polymorphism (RFLP) analysis was carried out on nuclear ribosomal DNA (rDNA) of the redfishes Sebastes fasciatus and Sebastes mentella from the Gulf of St. Lawrence in an attemps to describe new molecular markers that would discriminate these two sibling species. The RFLP analysis revealed heterogeneity in the size of the repeat unit within and among individuals that is most likely the result of variation in the length of the intergenic spacer. Double digestion of rDNA with the restriction enzymes EcoRI and ScaI and subsequent hybridization with a 28S probe revealed the presence of three patterns of fragments. Two fragment gourps seem to characterize S. mentella and S. fasciatus. Both fragment groups were present in several specimens, suggesting either a restriction-site polymorphism in S. mentella or a hybrid origin for these redfish. Discriminant analysis clearly differentiated all three rDNA patterns. Comparisons of genetic variations at the MDH locus and of the number of soft rays in the anal fin among the three rDNA-defined groups suggest that if the individuals showing the two groups of fragments are hybrids between S. fasciatus and S. mentella, introgression has also occurred in the Gulf of St. Lawrence©1999 National Research Council Canada

SAINTE-MARIE, B., N. URBANI, J.-M. SÉVIGNY, F. HAZEL, U. KUHNLEIN, 1999. Multiple choice criteria and the dynamics of assortative mating during the first breeding season of female snow crab Chionoecetes opilio (Brachyura, Majidae). Mar. Ecol. Prog. Ser., 181: 141-153 .

ROQUES, S., D. PALLOTTA, J.-M. SÉVIGNY, L. BERNATCHEZ, 1999. Isolation and characterization of polymorphic microsatellite markers in the North Atlantic redfish (Teleostei : Scorpaenidae, genus Sebastes). Mol. Ecol., 8: 685-702 .

SEVIGNY, J.-M., L. SAVARD, D.G. PARSONS, 1999. Genetic characterization of the northern shrimp Pandalus borealis, in the Northwest Atlantic. NAFO SCR Doc., 99/89, 16 p .

TREMBLAY, R., B. MYRAND, J.-M. SÉVIGNY, P. BLIER, H. GUDERLEY, 1998. Bioenergetic and genetic parameters in relation to susceptibility of blue mussels, Mytilus edulis (L.) to summer mortality. J. Exp. Mar. Biol. Ecol., 221: 27-58 .

URBANI, N., B. SAINTE-MARIE, J.-M. SÉVIGNY, D. ZADWORNY, U. KUHNLEIN, 1998. Sperm competition and paternity assurance during the first breeding period of female snow crab (Chionoecetes opilio) (Brachyura : Majidae). Can. J. Fish. Aquat. Sci., 55: 1104-1113 .

Two highly polymorphic microsatellite DNA loci were used to determine paternity of primiparous snow crab Chionoecetes opilio females. In addition, female spermathecal contents were genotyped at the two loci and histological analysis of the organs was carried out to elucidate patterns of sperm competition. Spermathecal contents from wild-caught females were cut into several cross sections and each section genotyped individually. Both wild and laboratory females commonly mated with several males whose ejaculates were stored and stratified in the spermathecae. Genetic typing of the offspring of laboratory-reared females revealed single paternity and indicated that the last mate to inseminate a female before oviposition gained paternity of the clutch. The predominant mechanism ensuring single paternity appeared to be sperm stratification. In wild-caught females, the microsatellite typing of the offspring also revealed single paternity, but larvae appeared to be sired by males whose genotypes were found in the spermathecal cross sections towards the dorsal end (blind end) of the spermathecae. This suggested that they were the first males to mate with females that they guarded until oviposition, and females remated with other males thereafter.

URBANI, N., B. SAINTE-MARIE, J.-M. SÉVIGNY, D. ZADWORNY, U. KUHNLEIN, 1998. Mating dynamics of the snow crab (Chionoecetes opilio, Brachyura : Majidae) : an analysis using DNA microsatellite markers. Pages 241-244 in Le Gal & Halvorson (ed.). New developments in marine biotechnology. Plenum Press, New York .

TREMBLAY, R., MYRAND, B., J.-M. SÉVIGNY, 1998. Genetic characterization of wild and suspension-cultured blue mussels (Mytilus edulis Linneaus, 1758) in the Magdalen Islands (Southern Gulf of St. Lawrence, Canada). J. Shellfish Res., 17: 1191-1202 .

URBANI, N., J.-M. SÉVIGNY, B. SAINTE-MARIE, D. ZADWORNY, U. KUHNLEIN, 1998. Identification of microsatellite markers in the snow crab Chionoecetes opilio. Mol. Ecol., 7: 357-358 .

SAINTE-MARIE, B., J.-M. SÉVIGNY, Y. GAUTHIER, 1997. Laboratory behavior of adolescent and adult males of the snow crab (Chionoecetes opilio) (Brachyura : Majidae) mated noncompetitively and competitively with primiparous females. Can. J. Fish. Aquat. Sci., 54: 239-248 .

In the laboratory, virgin females of snow crab (Chionoecetes opilio) were placed singly with one or two males to investigate mating behavior. Physiologically mature males, both adolescent and adult mated with females. Typically, matings comprised a precopulatory period, one or more copulations, and a postcopulatory period during which the female extruded eggs. Some females copulated after oviposition. In noncompetitive mating, adult males of 40-60 mm carapace width had repeated but brief copulations, while adult males of 120-140 mm carapace width had one long copulation. In pairs of competing adult males, large body size was an advantage both in taking over a female from a rival and in preventing female takeover by a rival. In competitions between an adult male and a larger adolescent male, the adult was more likely to dispossess his rival or revent takeover. The variance in mass of ejaculate stored by females was explained (98 %) by total copulatory time and number of copulations. Females with two mates obtained more copulations and larger ejaculate stores than females with one mate, suggesting that interannual variability in ejaculate stores reported for wild females is related to the level of male sexual competition.

SAINTE-MARIE, B., J.-M. SÉVIGNY, B.D. SMITH, G.A. LOVRICH, 1996. Recruitment variability in snow crab (Chionoecetes opilio) : pattern, possible causes, and implications for fishery management. Pages 451-478 In High latitude crabs : biology, management and economics : proceedings of the International Symposium. University of Alaska Fairbanks (Alaska Sea Grant report, 96-02) .

SÉVIGNY, J.-M., B. SAINTE-MARIE, 1996. Electrophoretic data support the last-male sperm precedence hypothesis in the snow crab, Chionoecetes opilio (Brachyura : Majidae). J. Shellfish Res., 15: 437-440 .

WYNGAARD, G.A., I.A. McLAREN, M.M. WHITE, J.-M. SÉVIGNY, 1995. Unusually high numbers of ribosomal RNA genes in copepods (Arthropoda : Crustacea) and their relationship to genome size. Genome, 38: 97-104 .

TALBOT, A., J.-M. SÉVIGNY, 1994. Caractéristiques de la population de flétan du Groenland (Reinhardtius hippoglossoides) du fjord du Saguenay. Pages 65-76 in J.-M. Sévigny & C.M. Couillard (éd.). Le fjord du Saguenay : un milieu exceptionnel de recherche. Ministère des pêches et des océans (Rapp. manus. can. sci. halieut. aquat., 2270) .

ANGERS, A., F. POTHIER, J.-M. SÉVIGNY, B. SAINTE-MARIE, 1994. Tissue specificity and ontogeny of lactate dehydrogenase in snow crab, Chionoecetes opilio (Brachyura, Majidae). Comp. Biochem. Physiol., 108B: 385-395 .

SÉVIGNY, J.-M., C.M. COUILLARD, 1994. Le fjord du Saguenay : un milieu exceptionnel de recherche. Rapp. manus. can. sci. halieut. aquat., 2270, 118 p .

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The objectives of the symposium were to bring up-to-date scientific knowledge related to the Saguenay fjord and to point out the main fields where research should be pursued in order to improve understanding of this environment. An additional objective of this symposium was to provide a forum to describe and discuss the marine park development project.

HODSON, P.V., E. PELLETIER, R. McLEOD, J. HELLOU, B. SAINTE-MARIE, C.M. COUILLARD, J.-M. SÉVIGNY, 1994. Chemical contamination of surface sediments and biota of the Saguenay Fjord. Pages 97-104 in J.-M. Sévigny & C.M. Couillard (éd.). Le fjord du Saguenay : un milieu exceptionnel de recherche. Ministère des pêches et des océans (Rapp. manus. can. sci. halieut. aquat., 2270) .

TALBOT, A., A. BOURGEOIS, J.-M. SÉVIGNY, 1994. Biologie du sébaste atlantique (Sebastes sp.) dans le fjord du Saguenay. Pages 77-82 in J.-M. Sévigny & C.M. Couillard (éd.). Le fjord du Saguenay : un milieu exceptionnel de recherche. Ministère des pêches et des océans (Rapp. manus. can. sci. halieut. aquat., 2270) .

SÉVIGNY, J.-M., 1994. Conservation of genetic diversity of marine organisms. Pages 103-108 in L. Gendron & S. Robinson (ed.). The development of underutilized invertebrate fisheries in Eastern Canada. Dept. of Fisheries and Oceans (Can. Man. Rep. Fish. Aquat. Sci., 2247) .

SÉVIGNY, J.-M., 1994. Variation génétique chez le flétan du Groenland (Reinhardtius hippoglossoides) et la crevette nordique (Pandalus borealis) du fjord du Saguenay. Pages 50-62 in J.-M. Sévigny & C.M. Couillard (éd.). Le fjord du Saguenay : un milieu exceptionnel de recherche. Ministère des pêches et des océans (Rapp. manus. can. sci. halieut. aquat., 2270) .

SAVARD, L., S. HURTUBISE, J.-M. SÉVIGNY, 1993. Les nouvelles unités de gestion de la pêche à la crevette nordique (Pandalus borealis) dans le nord du golfe du Saint-Laurent. MPO, Document de recherche sur les pêches dans l'Atlantique, 93/21, 32 p .

The management units for the shrimp fishery were set up in the early 1980s, on the basis of the sectors known and exploited by fishermen. However, the expansion of the fishery in the course of that decade has called into question certain of the boundaries between these management units. A restructuring of the management units is therefore proposed, to make for a better match between the shrimp aggregations they support and the sectors exploited by fishermen. The four sites where there is higher abundance of shrimp are well isolated from each other. The units support all stages of shrimp development; this is an indication of their capacity to ensure a certain level of recruitment to the fishery. The preliminary results of genetic analyses done on shrimp caught at different sites in the Gulf do not enable us to formally identify genetically distinct populations. Thus there is a mixing, which may be more or less significant, among the management units.

SÉVIGNY, J.-M., G. ROSS, D. ARCHAMBAULT, É. PARENT, 1992. Genetic variation in Greenland halibut (Reinhardtius hippoglossoides) from the St. Lawrence system and Northwest Atlantic. CAFSAC Res. Doc., 92/99, 21 p .

An allozyme study was conducted to determine if Greenland halibut from the Gulf of St. Lawrence and the Northwest Atlantic area belong to genetically differentiated populations. Genetic variations were studied at 13 loci coding for 10 proteins. Results show a low degree of genetic differentiation in this species. Genetic differentiation among age groups within sampling sites is also weak, suggesting that the observed structure is temporally stable.

SÉVIGNY, J.-M., Y. De LAFONTAINE, 1992. Identification of redfish juveniles in the Gulf of St. Lawrence using genotypic specific variations. Pages 69-73 in Y. De Lafontaine, T. Lambert, G.R. Lilly, W.D. McKone & R.J. Miller (ed.). Juvenile stages : the missing link in fisheries research : report of a workshop. DFO (Can. Tech. Rep. Fish. Aquat. Sci., 1890) .

DROUIN, G., J.-M. SÉVIGNY, I.A. McLAREN, J.D. HOFMAN, W.F. DOOLITTLE, 1992. Variable arrangement of 5S ribosomal genes within the ribosomal DNA repeats of arthropods. Mol. Biol. Evol., 9: 826-835 .

ROBY, D., J.D. LAMBERT, J.-M. SÉVIGNY, 1991. Morphometric and electrophoretic approaches to discrimination of capelin (Mallotus villosus) populations in the Estuary and Gulf of St. Lawrence. Can. J. Fish. Aquat. Sci., 48: 2040-2050 .

LAMBERT, J.-D., D. ROBY, J.-M. SÉVIGNY, 1990. Étude de la discrimination des populations de capelan (Mallotus villosus) des divisions 4RST de l'OPANO. CSCPCA doc. rech., 90/38, 46 p .

An evaluation of the degree of differentiation of capelin populations in the northern Gulf of St. Lawrence is undertaken using conventional and truss morphometric analyses and electrophoretic analysis of the genetic structure of eight samples of spawning fish taken in NAFO divisions 4RST. While the results of conventional morphometric analyses are not conclusive, truss and electrophoretic analyses tend to differentiate the sampled sites along an east-west axis. However, La Tabatière differs from this trend. The age structure at this site is peculiar and local fishermen report the occurrence of a different type of capelin ("blue back"). The results suggest that the actual bases for the definition of capelin management units in the northern Gulf of St. Lawrence, in NAFO divisions 4RST, are inadequate and that a distribution of the management units along an east-west axis would be more appropriate for the conservation of the biological integrity of capelin populations of the northern Gulf of St. Lawrence.

McLAREN, I.A., E. LABERGE, C.J. CORKETT, J.-M. SÉVIGNY, 1989. Life cycles of four species of Pseudocalanus in Nova Scotia. Can. J. Zool., 67: 552-558 .

The primarily arctic Pseudocalanus acuspes, relict in Bedford Basin, Nova Scotia, produces a first generation (G₁) in late winter; most G₁ individuals mature in late spring. The G₁ then produces a G₂, most of which "rest" in copepodite stages III and IV until early winter. These stages store large amounts of lipid in early summer, which slowly diminish subsequently. A small number of G₂ individuals continue to develop at temperature-dependent rates, maturing in early autumn and producing G₃ adults in November. Copepodites developing in winter and spring store less lipid. The primarily arctic Pseudocalanus minutus, rare in Bedford Basin and on the Scotia Shelf, is strictly annual, developing to a lipid-filled copepodite stage V after spawning in late winter. The arctic–temperate Pseudocalanus newmani is abundant on the Scotian Shelf, but may not be self-sustaining when advected into Bedford Basin. It stores little lipid and appears to have at least three mature generations at temperature-dependent intervals over Browns Bank between May and November. It may rest in winter, or its life-cycle synchrony by spring could result from food-limited development during winter. The temperate Pseudocalanus moultoni appears to have a life cycle similar to that of P. newmani, but was less common during summer on Browns Bank. These life cycles are appropriately adapted to the geographical ranges of the species, and show some parallels with species of Calanus.©1989 National Research Council Canada