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Recent genomic study on Greenland halibut Reinhardtius hippoglossoides throughout the Northwest Atlantic revealed genetic differentiation between the Gulf of St. Lawrence and the remainder of the Northwest Atlantic. Knowledge of migration and thus connectivity among fish populations is key to understanding the stock dynamics of commercial species and establishing effective management strategies. In this study, we use otolith microchemistry to assess the population structure and define more clearly the potential connectivity of Greenland halibut among Saguenay Fjord, the Estuary, and the Gulf of St. Lawrence (EGSL) and outside this system. Otolith margins and cores were analyzed to determine the elemental fingerprints. The margin elemental fingerprints (Mg, Sr, and Ba) were used to infer spatial differentiation, and quadratic discriminant analysis resulted in an overall reclassification success of fish to their capture site of 59%. The core elemental fingerprints indicated three chemically distinct juvenile sources, suggesting high connectivity in the EGSL supporting the St. Lawrence Estuary as a main nursery. Our results also suggest that one of these three sources has a smaller contribution relative to the other sites. Key words: Reinhardtius hippoglossoides, otolith microchemistry, elemental fingerprint, natal sources, stock contribution, 1. Introduction Coastal communities depend on the exploitation of fishery resources to support their economies. Sustainable fishing practices must be used by the fishing industry to limit the risk of [...]

Introduction: Arctic marine ecosystems are changing rapidly, largely due to the observed accelerated warming that is associated with ongoing climate change. Environmental DNA (eDNA) combined with metabarcoding has great potential for large-scale biomonitoring of Arctic marine communities. However, important limitations remain, such as understanding the complexity and drivers of spatiotemporal variation in eDNA distribution. Methods: In this study, we investigated the effect of tidal dynamics on aquatic metazoan (vertebrates and invertebrates) on eDNA metabarcoding results from nearshore estuarine and marine Arctic ports of Churchill (Manitoba) and Milne Inlet (Nunavut), respectively. We collected and sequenced 54 water samples per port at low, middle and high tide across three days, as well as two depths (surface, bottom), using four universal primer pairs (two primers in the COI gene and two in the 18S rRNA gene). Results: We observed a significant transition in the estuarine community structure from low to high tide, whereas the marine community structure was more stable across tides. The eDNA community structure differed between the surface and bottom waters in both the estuarine and marine ecosystems. However, the biodiversity pattern within the water column was significantly different between estuarine and marine ecosystems. Finally, we observed short-term temporal variation of the communities in both systems. Discussion: Altogether, our results highlight the short-term temporal dynamic nature of eDNA derived from coastal communities. This variability should be accounted for in eDNA sampling design to ensure robust characterization of coastal communities and long-term time series, particularly for estuarine environments where the effects of tide and depth are more important. [ABSTRACT FROM AUTHOR]

In the context of climate change, it is crucial to understand whether animals that have been domesticated and (or) selected maintain their abilities to adapt to changes in their thermal environment. Here, we tested how selection for absence of early sexual maturation combined with better growth performance may have impacted thermal resistance and gene expression response in the presence of thermal stress in brook charr Salvelinus fontinalis (Mitchill, 1814). We performed temperature challenge tests on brook charr 0+ juveniles and studied the expression of genes involved in the response to oxidative stress, in synthesis of heat shock proteins, or involved in regulation of apoptosis, in heart and liver tissues. Juveniles from the selected lineage had a higher thermal resistance than controls and a loss of equilibrium occurred on average 1 °C above what was observed for the controls. The relative expressions of catalase and HSP70 were significantly higher in juveniles from the selection program. Overall, thermally sensitive fish were characterized by low mass and length and lower relative expressions of genes associated with stress response. Our results indicate that selection for traits of interests may be indirectly related to the significant lineage effect on growth in early stages of development. [ABSTRACT FROM AUTHOR]

Determination of population structure and stock identification is a ubiquitous problem in fisheries assessment and management. Pacific salmon fishery management regimes are evolving to require higher resolution of stock composition on increasingly smaller reporting units. For coho salmon (Oncorhynchus kisutch), a stock identification baseline composed of some 57 982 individuals from 332 populations ranging from southeast Russia to California was employed for genetic stock identification (GSI). GSI analysis based upon variation at up to 480 single nucleotide polymorphisms (SNPs) was demonstrated to provide accurate estimates of stock composition for 37 conservation units (CU) in British Columbia, 13 reporting groups in the United States, and one reporting group in Russia. In many instances, accurate population-specific estimates of stock composition within a CU were possible in fishery samples, as well as identifying individuals to some specific populations. A genetics- based assessment system provides an opportunity for conservation-based management of Canadian coho salmon. La determination de la structure des populations et l'identification au stock sont des problemes generalises en evaluation et en gestion des peches. Les regimes de gestion des peches aux saumons du pacifique evoluent pour exiger une plus haute resolution de la composition des stocks dans des unites de declaration de plus en plus petites. Pour le saumon coho (Oncorhynchus kisutch), une base de reference pour l'identification au stock comprenant quelque 57 982 individus provenant de 332 populations allant du sud-est de la Russie a la Californie a ete utilisee pour l'identification genetique au stock (IGS). Il est demontre que l'analyse IGS basee sur les variations de jusqu'a 480 polymorphismes mononucleotidiques (SNP) fournit des estimations exactes de la composition des stocks pour 37 unites de conservation (UC) en Colombie-Britannique, 13 groupes de declaration aux Etats-Unis et un groupe de declaration en Russie. Dans de nombreux cas, des estimations propres a la population exactes de la composition des stocks au sein d'une UC sont possibles pour des echantillons tires de la peche, ainsi que l'affectation des individus a certaines populations precises. Un systeme devaluation reposant sur la genetique offre la possibilite d'une gestion basee sur la conservation des saumons cohos canadiens. [Traduit par la Redaction], Introduction The general objective of genetic stock identification (GSI) for Pacific salmon is to provide the optimal resolution among stocks or populations present when applied to mixed-stock fishery and forensic [...]