INTRAPOPULATION FEEDING DIVERSITY IN BLUE TILAPIA - EVIDENCE FROM STABLE-ISOTOPE ANALYSES

Stable carbon and nitrogen isotopes (delta(13)C and delta(15)N) in ani mal tissues are largely determined by isotope composition of assimilat ed food. Variations in delta(13)C and delta(15)N values within a fish population are often small as a result of feeding on the same food sou rce. We report here, however, strikingly broad ranges of delta(13)C (- 25.9 to -9.5 parts per thousand) and delta(15)N (5.8 to 14.4 parts per thousand) in an exotic fish from a Florida lake. Together with isotop e data for food sources and gut contents, we demonstrate significant d iet variation within a population of blue tilapia.