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Aquatic Biology

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AB 8:137-144 (2010)  -  DOI:

Dietary breadth and trophic position of introduced European catfish Silurus glanis in the River Tarn (Garonne River basin), southwest France

J. Syväranta1,3,*, J. Cucherousset1,4, D. Kopp1,5, A. Crivelli2, R. Céréghino1, F. Santoul1

1EcoLab, UMR 5245 (CNRS-UPS-INPT), Université de Toulouse, bât 4R3, 118, route de Narbonne,
31062 Toulouse Cedex 9, France
2Station biologique de la Tour du Valat, Le Sambuc, 13200 Arles, France
3Present address: Department of Biological and Environmental Science, PL35, 40014 University of Jyväskylä, Finland
4Present address: Centre for Conservation Ecology and Environmental Change, School of Conservation Sciences, Bournemouth University, Poole, Dorset BH12 5BB, UK
5Present address: IFREMER, Equipe Ecologie et Modéles pour l’Halieutique, Rue de l’Ile d’Yeu, BP 21105,
44311 Nantes Cedex 3, France

ABSTRACT: Although being a widely introduced and successfully established species, the European catfish Silurus glanis L. (the world’s third largest freshwater fish) remains poorly studied in its introduced areas. Here we studied the trophic ecology of non-native European catfish in a large river system in south-western France using stomach content and stable isotope analyses (SIA). We used fin samples for SIA of catfish and hence tested the validity of using fin tissue as a proxy for muscle in SIA. The mean δ15N and δ13C values analysed from fin tissues did not differ from those analysed from muscle tissue and reflected strong and consistent relationships (r2 = 0.95 for carbon and r2 = 0.98 for nitrogen). The δ15N values varied almost 5‰ among the analysed catfish individuals, while δ13C values varied >5‰. Total length of these catfish ranged from 200 to 2240 mm and was correlated with δ15N and especially with δ13C values. Although catfish length and δ15N values were positively correlated, the mean trophic positions of catfish increased only slightly from smaller individuals to larger ones (4.3 to 4.7). However, larger catfish were considerably 13C-enriched in their δ13C values compared to smaller individuals and had up to 4‰ higher δ13C values than their expected aquatic prey. This might indicate frequent consumption of mammals and/or non-aquatic birds by the larger sized individuals, which were found in the catfish stomachs.

KEY WORDS: Stable isotopes · Introduced species · Top predator · River · Food web · Fin clips

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Cite this article as: Syväranta J, Cucherousset J, Kopp D, Crivelli A, Céréghino R, Santoul F (2010) Dietary breadth and trophic position of introduced European catfish Silurus glanis in the River Tarn (Garonne River basin), southwest France. Aquat Biol 8:137-144.

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