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Marine Ecology Progress Series

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MEPS 554:157-171 (2016)  -  DOI:

Linking small pelagic dietary shifts with ecosystem changes in the Gulf of Lions

Pablo Brosset1,2,*, Baptiste Le Bourg3,5, David Costalago4, Daniela Bănaru3, Elisabeth Van Beveren2, Jean-Hervé Bourdeix2, Jean-Marc Fromentin2, Frédéric Ménard3, Claire Saraux2

1Université de Montpellier, UMR MARBEC (IRD, Ifremer, UM, CNRS), 34203 Sète cedex, France
2IFREMER, UMR MARBEC (IRD, Ifremer, UM, CNRS), 34203 Sète cedex, France
3Mediterranean Institute of Oceanography (MIO), Aix-Marseille Université/CNRS/IRD/Université de Toulon, UM 110, 13288 Marseille, France
4Department of Ecology, Environment and Plant Sciences, Stockholm University, 10691 Stockhom , Sweden
5Present address: Université de Liège, Laboratory of Oceanology, MARE Centre, 4000 Liège, Belgium
*Corresponding author:

ABSTRACT: Since 2008, a severe decrease in size and body condition together with a demographic truncation has been observed in the sardine (secondarily in anchovy) population of the Gulf of Lions (NW Mediterranean Sea). In parallel, sprat biomass, which was negligible before, has increased tenfold. All of these changes have strongly affected the regional fisheries. Using trophic and isotopic data from contrasting periods of low versus high growth and condition, we investigated potential changes in diet and interspecific feeding interactions through time. Evidence of resource partitioning was found between sprat and both anchovy and sardine in 2004 and 2005. Since 2010, the isotopic niches of the 3 species have tended to overlap, suggesting higher risk of competition for food resources. Moreover, the wider trophic niche of sprat indicates higher variability in individual diets. Anchovy and sardine diet varied through time, with a high proportion of large copepods or cladocerans in periods of high growth and condition (1994 and 2007, respectively) versus a dominance of small copepods in the present (2011-2012). Furthermore, an important reduction in prey diversity was also identified in the diet of both anchovy and sardine during the most recent period. Our results support the hypothesis that changes in small pelagic fish growth, size and body condition and ultimately biomass could be due to bottom-up control characterized by changes in food availability and increasing potential trophic competition.

KEY WORDS: Trophic ecology · Anchovy · Sardine · Sprat · Dietary overlap · NW Mediterranean

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Cite this article as: Brosset P, Le Bourg B, Costalago D, Bănaru D and others (2016) Linking small pelagic dietary shifts with ecosystem changes in the Gulf of Lions. Mar Ecol Prog Ser 554:157-171.

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