Effects of body size and environment on diet-tissue δ13C fractionation in fishes

delta C-13 data are often used in trophodynamic research where diet-tissue fractionation (Delta delta C-13) is assumed to be 0-1%. per trophic level and unaffected by the size of animals or their environment. Variation in Delta delta C-13 Will influence conclusions about food sources, energy pathways and trophic level. To assess the effects of body size, age and environmental conditions on Delta delta C-13, European sea bass (Dicentrarchus labrax) were reared on constant diets of dab (Limanda limanda) or (Ammodytes marinus) for 2years under natural environmental regimes. Bags were sampled approximately monthly to determine Delta delta C-13 for muscle, heart and liver tissue and were 1.66 parts per thousand, -0.18 parts per thousand, -1.77 parts per thousand (sandeel diet) and 1.34 parts per thousand, -1.18 parts per thousand, -1.75 parts per thousand (dab diet) respectively. Arithmetic lipid correction increased Delta delta C-13 to > 2%o for muscle and liver. Delta delta C-13 was dependent on body mass and experimental duration (age) and generally declined with weight or time even after correction for lipid content. For liver, increasing temperature increased Delta delta C-13. The Delta delta C-13 estimates from this study were compared with all available published A613 C estimates for fish. Bass muscle A Delta delta C-13 was similar to previous estimates for fish white muscle Delta delta C-13 (1.56 +/- 1.10%o) and whole body Delta delta C-13 (1.52 +/- 1.13%o). Fractionations derived in this study, combined with those from the literature, support the use of diet-tissue fractionation values of between 1 parts per thousand-2 parts per thousand for delta C-13, rather than the commonly used 0 parts per thousand - 1 parts per thousand. For muscle Delta delta C-13, 1.5 parts per thousand is appropriate. (c) 2007 Elsevier B.V. All rights reserved.