Effects of Supplemental Feeding on Diel Patterns of Gut Fullness, Diet Composition, and Digestive Enzyme Activities of Juvenile Channel Catfish

Channel Catfish nursery ponds receive daily additions of commercial feeds to enhance fish production. However, zooplankton and insects in ponds support early-life fish growth. To improve feeding methods, a pond experiment was conducted to test the effects of supplemental feeding on ontogenetic changes in diel feeding activity, diet composition, and digestive enzyme activities of fish. Floating, open-topped cages fitted with mesh were constructed to retain the fish, but allow live prey to enter. The cages were deployed in a pond, stocked with 10-day-old fish (1.5 fish/L), and randomly assigned to treatments that received feed once daily at midday, or did not receive any feed (4 cages/treatment). Once weekly for 4 weeks, fish were collected over 24 hours at 3 hour intervals. Fish growth in length and weight did not differ between treatments (P ≥ 0.20). Fish foraged most actively at 12pm and 12am in both treatments. Measurements of digestive enzyme activities (including amylase, trypsin, and pepsin) are ongoing. Initial results show that enzyme activities changed over a diel cycle and were highly variable among individuals. This study supports growing evidence that supplemental feeding may be unnecessary during early life in Channel Catfish nursery ponds.