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In the Northwest Atlantic (NWA), the Atlantic mackerel (Scomber scombrus) has a northern and a southern contingent, which spawn in Canada and the United States (U.S.), respectively. Both contingents mix mostly along the U.S. shelf during overwintering. The discrimination of individuals from each contingent in fisheries could improve the management of this depleted species in both countries. Here, we used genome-wide markers (>10 000 single nucleotide polymorphisms (SNPs)) to assess genomic differences between mackerel of both contingents, and possibly infer the proportions of each contingent in NWA management units. Small but significant genetic differentiation was observed between the northern and southern contingents ([F.sub.ST] = 0.0010). Genetic assignments to reference samples from the two contingents were performed with predictive accuracy > 85%. Fish from both contingents were present along the U.S. shelf during late winter and early spring but also, without prior evidence of this, likely in Canadian waters from late spring to fall. Genetic assignments could be used as a stock discrimination tool so that fishery removals can be effectively determined and managed on a contingent level. Key words: population genomics, fisheries, Scombridae, migratory, pelagic, fish, Introduction Defining the population structure of marine migratory fish species is challenging. Long-distance migrants may cross multiple management jurisdictions each year and have multiple spawning areas (e.g., Puncher et al. [...]

The Atlantic mackerel (Scomber scombrus) is a migratory, small pelagic species that supports important fisheries throughout the North Atlantic Ocean. In recent decades, the majority of worldwide landings of Atlantic [...]

Predation is a substantial source of mortality that is a function of the abundance of predator and prey species. This source of mortality creates a challenge of incorporating species interactions in statistical catch-at-age models in a way that accounts for the uncertainty in input data, parameters, and results. We developed a statistical, age-structured, multispecies model for three important species in the Georges Bank fish community: Atlantic cod (Gadus morhua), silver hake (Merluccius bilinearis), and Atlantic herring (Clupea harengus). The model was fit to commercial catch, survey, and diet data from 1978 to 2007. The estimated predation rates were high, compared with fishing mortality, and variable with time. The dynamics of the three species can be explained by the interplay between fishing and predation mortality. Monte Carlo simulations were used to evaluate the ability of the model to estimate parameters with known error introduced into each of the data types. The model parameters could be estimated with confidence from input data with error levels similar to those obtained from the model fit to the observed data. This evaluation of model performance should help to move multispecies statistical catch-at-age models from proof of concept to functional tools for ecosystem-based fisheries management. La predation est une importante source de mortalite qui depend de l'abondance des especes predatrices et proies. Cette source de mortalite necessite l'integration dans les modeles statistiques de capture a l'age de l'interaction des especes d'une maniere qui tienne compte de l'incertitude associee aux donnees d'entree, aux parametres et aux resultats. Nous avons elabore un modele statistique multispecifique structure selon l'age pour trois especes importantes de la communaute de poissons du banc Georges, a savoir la morue(Gadus morhua), le merlu argente (Merluccius bilinearis) et le hareng de l'Atlantique (Clupea harengus). Le modele a ete compare a des donnees de prises commerciales, de donnees de campagne pour la periode de 1978 a 2007. Les taux de predation estimes etaient eleves par rapport a la mortalite par peche et variaient dans le temps. La dynamique des trois especes peut s'expliquer par l'influence reciproque de la mortalite par peche et de la mortalite par predation. Des simulations de Monte Carlo ont ete utilisees pour evaluer la capacite du modele a estimer les parametres auxquels sont associees des erreurs connues introduites dans chaque type de donnees. Les parametres modelises pouvaient etre estimes avec confiance a partir des donnees d'entree a des niveaux d'erreur semblables a ceux obtenus en ajustant le modele aux donnees d'observation. A la lumiere de cette evaluation de leur performance, il est possible d'entrevoir l'utilisation de modeles statistiques multispecifiques de capture a l'age, toujours au stade de la validation de principe, comme outils fonctionnels de gestion ecosystemique des peches. [Traduit par la Redaction], Introduction Accounting for trophic interactions among species is an important component of an ecosystem approach to fisheries (Link 2010). Approaches for incorporating species interactions have expanded substantially over the last [...]