Stable Isotopes of Carbon and Nitrogen Reveal Live Prey Support of Juvenile Channel Catfish Reared Under Intensive Feeding Regimens in Ponds

Traditional guides for rearing juvenile channel catfish (Ictalurus punctatus) recommend intensive feeding from the time of fish stocking in ponds.  However, mounting evidence from recent studies suggest live prey may support fish growth.  To avoid wasteful overfeeding, we conducted experiments in tanks and ponds to compare the contributions of live prey and commercial feed to fish growth.  Following a tank experiment to calibrate muscle tissue δ¹³C and δ¹⁵N value responses to known diets, we monitored muscle tissue δ¹³C and δ¹⁵N values of fish reared in the ponds with access to: (a) live prey only, (b) live prey with a low feeding rate, or (c) live prey with a high feeding rate.  We found that live prey entirely supported fish growth during the first 3 weeks in ponds, regardless of supplemental feeding rate. Thereafter, about 50% of fish growth was supported by feed, resulting in faster fish growth as compared to fish in ponds that did not receive feed.  Thus, live prey support fish growth throughout the first growing season, and feed supplements growth only several weeks after stocking in ponds. To improve production efficiency, we recommend managers withhold commercial feeds until several weeks after stocking fish in ponds.