Growth, Survival, and Body Composition of Sunshine Bass after a Feeding and Fasting Experiment

There is continuous interest in experimental, semipurified diet formulations and in the formulation of practical, inexpensive diets for grow out of sunshine bass (female white bass Morone chrysops × male striped bass M. saxatilis ). The effects of four diets on growth, survival, and body composition of sunshine bass after a feeding period (51 d) and a subsequent fasting period (14 d) were examined. To our knowledge, no previous sunshine bass feeding experiments have incorporated a fasting period to simulate the handling and acclimation conditions experienced by farmed fish that are stocked into new environments. Diets consisted of a high‐nutrient commercial diet, a wheat‐gluten‐based practical diet, a semipurified diet (meeting standard nutrient requirements), and a frozen natural diet (chironomids). Fish were hand fed three times per day at 4% of body weight. At the end of the fasting period, samples were collected for histological analysis of the liver and posterior intestine. Survival was significantly lower for fish that were fed the semipurified diet than for fish given the other three diets. The greatest growth was achieved by fish that received the commercial diet. Body composition was significantly affected by diet, and protein was depleted at a greater rate than lipid during the fasting period. Analysis suggests that during this short fasting period, sunshine bass utilized protein and glycogen before using lipid. Liver sections from fish that were given the commercial diet showed that (1) the hepatocytes contained larger lipid deposits than were observed in the frozen chironomid diet group and (2) the nuclei of the hepatocytes were pushed to the cell wall. Sections of the posterior intestine revealed significant differences among dietary treatment groups in the height of folds and number of goblet cells.