stable
isotopes as a tool for nutrient assimilation studies in larval fish feeding
on live food
Ch. Schlechtriem, U. Focken, K. Becker-2004
Aquatic Ecology, 38: 93-100
Abstract:
Many fish and crustacean larvae require live food at the onset of
exogenous feeding. It is generally difficult to include chemical or isotopic
markers in live food for nutrient studies. The soil nematode Panagrellus
redivivus, a potential live food for fish and crustacean larvae, can be mass
cultured on a wide range of media, which offers the opportunity to produce
isotopically distinct live food. In this study P. redivivus was cultured
separately on wheat- and corn-based media. As a result nematodes with
different stable carbon isotope signatures (δ13C) could be
obtained. Both types of nematodes were tested on first-feeding Cyprinus
carpio larvae in a feeding experiment lasting six days. In contrast to the
nematodes cultured on the wheat-based medium, the δ13C
values of nematodes produced on the corn-based medium were clearly different
to the isotopic signature of the fish larvae. δ13C values
for lipids and lipid-free matter of fish larvae sampled on Day 2, 4 and 6
after first feeding were clearly influenced by the stable isotopic pattern
of the nematodes. The assimilation of lipid and lipid-free matter was
calculated by a two source mixing model. The onset of nutrient retention as
well as the proceeding assimilation of feed carbon into the body tissues
could be calculated precisely for nematodes cultured on the corn-based
medium. The possibility to mass produce live food organisms with a
controllable isotopic signature provides new possibilities for nutritional
studies on fish and crustacean larvae.
(Department of Aquaculture Systems and Animal Nutrition in the Tropics
and Subtropics, Hohenheim University, Stuttgart, Germany, e-mail:
inst480@uni-hohenheim.de)