MEPS 400:207-219 (2010)  -  DOI:

Exploitation of trophic resources by fish under stressful estuarine conditions

Stéphanie Pasquaud1,*, Valérie David2, Jérémy Lobry1, Michel Girardin1, Benoît Sautour3, Pierre Elie1

1Cemagref, Estuarine Ecosystems and Diadromous Fish Research Unit, 50 avenue de Verdun 33612 Cestas Cedex, France
2UMR LIENSs 6250 CNRS/Université de La Rochelle, Institut du Littoral et de l’Environnement, 2 rue Olympes de Gouges, 17000 La Rochelle, France
3UMR 5805 EPOC–OASU, Université de Bordeaux 1, 2 Rue du Professeur Jolyet, 33120 Arcachon, France

ABSTRACT: Despite their high complexity and variability, estuaries are very productive and play an important role in fish feeding. We investigated how fish optimize their use of the available trophic resources by studying trophic preference variability and feeding strategies of some pelagic and demersal fish in the Gironde estuary (southwest France). Fish and their prey were collected approximately every 2 mo from July 2003 to June 2004 in the upstream area of the saline estuary. Stomach contents were analysed to assess the variability of fish feeding in relation to their size and the time of year. Intra- and interspecific food niche overlap was evaluated using Schoener’s index, and a cross-calculation method was used to highlight general fish trends in predation strategy. Stomach content results showed interspecific and intraspecific variability in feeding by fish, which can be explained by their different or ontogenetically changing ecomorphology. Their diets are composed mainly of zooplankton and hyperbenthic crustaceans, with temporal variations in the consumed taxa. Optimization of available trophic resource use, a key element in estuarine resilience, is thus possible due to the temporal adaptation of this structural trophic web. However, in spite of their temporal adaptation capacity, most fish species exhibited a specialist feeding strategy. This result was not expected. Since zooplankton and hyperbenthic crustaceans exhibit a low specific richness in estuaries, especially in the high turbidity of the Gironde estuary, the loss of one of these species could affect the fish trophic web structure and hence the resilience of the system.

KEY WORDS: Pelagic and demersal fish · Stomach contents · Diet composition · Feeding strategy · Prey characteristics · Estuarine ecosystem · Gironde estuary

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Cite this article as: Pasquaud S, David V, Lobry J, Girardin M, Sautour B, Elie P (2010) Exploitation of trophic resources by fish under stressful estuarine conditions. Mar Ecol Prog Ser 400:207-219.

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