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Recruitment of mackerel icefish (Champsocephalus gunnari) at South Georgia indicated by predator diets and its relationship with sea surface temperature

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Abstract:

The South Georgia population of mackerel icefish (Champsocephalus gunnari) is exploited by both a fishery and predators, including gentoo penguins (Pygoscelis papua). Because considerable uncertainty surrounds recent estimates of stock size, there is a need to consider novel approaches that may give insight into the population dynamics of this species. We derive two indices of recruitment based on the occurrence of mackerel icefish in gentoo penguin diets, one of which is scaled by a survey estimate of the density of Antarctic krill (Euphausia superba), an alternative prey species for gentoo penguins. The closure of the fishery for much of the 1990s allowed the relationship between environmental conditions and recruitment to be studied without the confounding effects of fishing mortality. The recruitment indices were positively correlated with sea surface temperature with a lag time equal to the age of the fish. These results suggest strong links between mesoscale environmental processes and the smaller scale interaction between gentoo penguins and their mackerel icefish prey.

La population de poissons des glaces (Champsocephalus gunnari) de la Géorgie du Sud est exploitée à la fois par la pêche commerciale et par des prédateurs, dont le manchot papou (Pygoscelis papua). Comme les estimations récentes de la taille du stock sont très incertaines, il est nécessaire d'utiliser de nouvelles avenues pour obtenir des perspectives sur la dynamique de population de cette espèce. Nous tirons deux indices de recrutement à partir de la fréquence des poissons des glaces dans le régime alimentaire des manchots papous, dont l'un est cadré d'après des estimations de densité basées sur des inventaires du krill antarctique (Euphausia superba), une espèce de proie de rechange des manchots papous. L'interdiction de la pêche pendant presque toute la décennie des années 1990 a permis d'étudier la relation entre les conditions du milieu et le recrutement sans les effets confondants de la mortalité due à la pêche. Il existe une corrélation positive entre les indices du recrutement et la température de la surface de la mer, avec un décalage qui correspond à l'âge des poissons. Ces résultats laissent croire qu'il existe de puissants liens entre les processus environnementaux à échelle moyenne et les interactions à petite échelle entre les manchots papous et leurs proies, les poissons des glaces.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: November 1, 2005

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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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