Performance of Cage-Raised, Overwintered Hybrid Striped Bass Fed Fish Meal- or Soybean-Based Diets

We conducted a 26-week study to evaluate the performance of cage-raised hybrid Striped Bass (female White Bass Morone chrysops x male Striped Bass M. saxatilis) fed fish meal (FM) and soybean (SOY; soybean meal + soy protein concentrate) based diets. A FM reference diet was formulated to contain crude protein (CP) at 450 g/kg, lipid at 120 g/kg, and an estimated digestible energy level of 13 MJ/kg. Two test diets (SOY and SOY+GBA) were formulated to replace 70% of the CP in the reference diet with SBM in the absence or presence of GroBiotic-A (GBA), a yeast-based prebiotic, at 20 g/kg. The other 12% of dietary FM in the reference diet was replaced with SPC in the test diets, further reducing FM inclusion to 70 g/kg. Each diet was fed to quadruplicate groups of 40 advanced juvenile hybrid Striped Bass (initial weight similar to 54 g/fish) stocked into each of twelve 1-m(3) floating cages, which were equally divided into four 0.05-ha, rubber-lined ponds according to a randomized complete block design. Caged fish in each pond were fed one of the randomly assigned diets to apparent satiation once daily. After 26 weeks of feeding, results showed that (1) the overall growth performance, survival, and feed efficiency of the fish were unaffected by diet; (2) the intraperitoneal fat ratio was significantly lower in fish that received the SOY-based diets; and (3) plasma glucose and lysozyme activity were significantly lower in fish that were fed the SOY-based diets, whereas plasma osmolality, hematocrit, neutrophil oxidative radical production (nitroblue tetrazolium test), and extracellular superoxide anion production of head-kidney macrophages were unaffected by diet. We conclude that low-FM, SOY-based diets can support adequate performance and normal physiological responses of hybrid Striped Bass during overwintering.