Stable isotope variability in tissues of the Eurasian perch Perca fluviatilis

Stable isotope analysis is frequently used as a complementary method of dietary analysis, to describe trophic relationships and assess food-web structure. These studies allow a precise determination, based on the calculation of a diet-tissue fractionation factor. The fractionation factor, determined for whole organisms or specific tissues, may vary substantially in natura. In the present study, delta C-13 and delta N-15 were assessed in lipid-free tissues (spleen, liver, viscera, scales, gills, spine, white muscle, brain) and in available energy reserves (proteins, glycogen, lipids) of Eurasian perch (Percafluviatilis) reared under controlled conditions and fed for 4 months with the same artificial diet. Some discrepancies in delta N-15 and delta C-13 data were observed among tissues, respectively up to 3.43%. and 2.54%. for 6"N and VC. The N-15 signature in organs depends on their metabolic activity. Despite a significant delta C-13 enrichment from feed to tissues, the lipids in spine, liver and viscera exhibit a certain stability. (c) 2007 Elsevier Inc. All rights reserved.