, Volume 115, Issue 3, pp 337–343

Metabolic fractionation of stable carbon isotopes: implications of different proximate compositions for studies of the aquatic food webs using δ13C data

  • U. Focken
  • K. Becker

DOI: 10.1007/s004420050525

Cite this article as:
Focken, U. & Becker, K. Oecologia (1998) 115: 337. doi:10.1007/s004420050525


In two laboratory experiments using tilapia (Oreochromis niloticus) and common carp (Cyprinus carpio), we investigated the effect of lipid content in the fish carcass on the stable carbon isotope ratio (δ13C). In both experiments, a significant negative correlation was found between lipid content in the carcass dry matter and δ13C of total dry matter, but there was no influence on the δ13C of fat-free dry matter or lipids. As the lipid content of fish is known to vary with reproductive stage, season or nutritional state, separate analysis of fractions of the proximate composition of dry matter will lead to more reliable results than analysing the whole body. The differences in δ13C between diet and fish carcass (trophic shift) were different for the two species, calling for feeding trials under controlled conditions using the species and the feeds in question before applying the stable isotope tracer technique in the analysis of food webs.

Key words Stable carbon isotopesFood web studiesMetabolic fractionationTrophic shiftProximate composition

Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • U. Focken
    • 1
  • K. Becker
    • 1
  1. 1.Department of Animal Nutrition and Aquaculture, Institute for Animal Production in the Tropics and Subtropics, Hohenheim University (480), D-70593 Stuttgart, Germany Fax: +49-711-459-3702; e-mail: focken@uni-hohenheim.deDE