STABLE ISOTOPIC EVALUATION OF THE RELATIVE ASSIMILATION OF NATURAL AND ARTIFICIAL FOODS BY GOLDEN SHINERS NOTEMIGONUS-CRYSOLEUCAS IN PONDS

Stable carbon isotope ratios (delta(13)C) were used to estimate the re lative contributions of natural and prepared feeds to the nutrition of golden shiners Notemigonus crysoleucas in ponds. Concurrent feeding t rials were conducted in tanks (110 L) and ponds (0.04 ha) to determine the response of golden shiners to three isotopically distinct prepare d diets both in the presence (pond) and absence (tank) of natural food . Seston was the primary indicator of the delta(13)C of natural foods available in the ponds, but delta(13)C's Of free-swimming, unfed golde n shiners provided an additional index. Fish receiving experimental di ets were maintained in floating nets within the same ponds. After 6 wk , fish in tanks fed all three diets had acquired the diet label to som e degree, while fish in ponds also tracked their respective feeds exce pt for those fed diet 3. This diet contained a large amount of corn me al, which appeared to be poorly assimilated by golden shiners. The use of natural foods by golden shiners fed all three prepared feeds range d from 40-83% and was inversely correlated with the relative assimilat ion of the prepared feeds.