MEPS 529:219-231 (2015)  -  DOI:

Influence of environmental variability and age on the body condition of small pelagic fish in the Gulf of Lions

Pablo Brosset1,2,*, Frédéric Ménard3, Jean-Marc Fromentin2, Sylvain Bonhommeau2, Caroline Ulses4, Jean-Hervé Bourdeix2, Jean-Louis Bigot2, Elisabeth Van Beveren2, David Roos2, Claire Saraux2

1University of Montpellier, UMR MARBEC (IRD, Ifremer, UM, CNRS), 34203 Sète cedex, France
2IFREMER, UMR MARBEC (IRD, Ifremer, UM, CNRS), 34203 Sète cedex, France
3IRD, Mediterranean Institute of Oceanography (MIO), Aix-Marseille Université/CNRS/IRD/Université de Toulon, UM 110, 13288 Marseille, France
4University of Toulouse 3, CNRS/INSU, Laboratoire d’Aérologie UMR 5560, 14 Avenue Edouard Belin, 31400 Toulouse, France
*Corresponding author:

ABSTRACT: Endogenous and environmental variables are fundamental in explaining variations in fish condition. Based on more than 20 yr of fish weight and length data, relative condition indices were computed for anchovy and sardine caught in the Gulf of Lions. Classification and regression trees (CART) were used to identify endogenous factors affecting fish condition, and to group years of similar condition. Both species showed a similar annual cycle with condition being minimal in February and maximal in July. CART identified 3 groups of years where the fish populations generally showed poor, average and good condition and within which condition differed between age classes but not according to sex. In particular, during the period of poor condition (mostly recent years), sardines older than 1 yr appeared to be more strongly affected than younger individuals. Time-series were analyzed using generalized linear models (GLMs) to examine the effects of oceanographic abiotic (temperature, Western Mediterranean Oscillation [WeMO] and Rhône outflow) and biotic (chlorophyll a and 6 plankton classes) factors on fish condition. The selected models explained 48 and 35% of the variance of anchovy and sardine condition, respectively. Sardine condition was negatively related to temperature but positively related to the WeMO and mesozooplankton and diatom concentrations. A positive effect of mesozooplankton and Rhône runoff on anchovy condition was detected. The importance of increasing temperatures and reduced water mixing in the NW Mediterranean Sea, affecting planktonic productivity and thus fish condition by bottom-up control processes, was highlighted by these results. Changes in plankton quality, quantity and phenology could lead to insufficient or inadequate food supply for both species.

KEY WORDS: Anchovy · Sardine · Relative condition factor · NW Mediterranean Sea · Endogenous effect · Environmental effect

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Cite this article as: Brosset P, Ménard F, Fromentin JM, Bonhommeau S and others (2015) Influence of environmental variability and age on the body condition of small pelagic fish in the Gulf of Lions. Mar Ecol Prog Ser 529:219-231.

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