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Reproductive interactions between fugitive farmed and wild Atlantic cod (Gadus morhua) in the field

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Abstract:

Atlantic cod (Gadus morhua) are being increasingly farmed in net pens adjacent to coastal populations that are currently at historic lows. One concern is that farmed escapees enter local spawning shoals and mate with wild cod. We tested for the potential of escaped farmed cod to interact and hybridize with wild fish by examining the spatial dynamics of, and associations between, fish tagged with ultrasonic transmitters. Based on these data, we also investigated the basic mating system of cod in the field. The spawning ground was best described as a lekking arena. Wild males aggregated near the seafloor and associations between individuals were frequent. Wild females had a pelagic and dispersed distribution and rarely associated with each other. Associations between individual wild males and females were also infrequent. Farmed males rarely associated with wild fish and had core usage areas above the wild males, suggesting that they were not admitted into the spawning arena. Farmed females were over the spawning arena more frequently than wild females and often associated with wild males at the depth of the spawning arena, indicating potential mating with wild males and the possibility of courtship interference. Hence, hybridization between escaped farmed and wild cod is likely.

On fait de plus en plus d’élevages de morues (Gadus morhua) dans des enclos en filet près des populations côtières qui se retrouvent actuellement à des densités historiquement basses. On se préoccupe de ce que des poissons échappés d’élevage se joignent aux bancs locaux de reproducteurs et frayent avec des morues sauvages. Nous avons testé la possibilité que des morues échappées d’élevage interagissent et s’hybrident avec les poissons sauvages en examinant la dynamique spatiale et les associations de poissons marqués d’une étiquette émettrice d’ultrasons. Avec ces données, nous avons aussi étudié le système d’appareillade de base des morues en nature. Les zones de fraie peuvent le mieux être décrites comme des arènes de lek. Les mâles sauvages se rassemblent près du fond marin avec de fréquentes associations entre individus. Les femelles sauvages ont une répartition pélagique et dispersée et s’associent rarement l’une à l’autre. Les associations entre des individus sauvages mâles et femelles sont aussi peu fréquentes. Les mâles d’élevage s’associent rarement aux poissons sauvages et leurs zones principales d’utilisation se situent au-dessus de celles des mâles sauvages, ce qui laisse croire qu’ils ne sont pas admis dans l’arène de fraie. Les femelles d’élevage se retrouvent au-dessus de l’arène de fraie plus fréquemment que les femelles sauvages et s’associent fréquemment à des mâles sauvages dans le fond de l’arène de fraie, ce qui indique la possibilité d’une appareillade avec les mâles sauvages et de comportements de cour d’interférence. L’hybridation entre les morues échappées de culture et les morues sauvages est donc probable.

Document Type: Research Article

Publication date: August 1, 2010

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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