Use of tunicate meal (pleated sea squirt Styela plicata) protein as a partial replacement of menhaden fish meal protein in the diet of juvenile Black Sea Bass

ObjectiveThe pleated sea squirt Styela plicata (subphylum Tunicata), an invasive marine invertebrate in coastal waters of southeastern North Carolina, was investigated as an alternative protein source to fish meal (FM) in the diet of juvenile Black Sea Bass Centropristis striata. MethodsSix different isoproteic and isolipidic diets were formulated to replace 0.0, 8.3, 16.7, 25.0, 33.3, and 41.6% of FM protein with tunicate meal (TM) protein by supplementing 0, 5, 10, 15, 20, and 25% TM in the diets. The experimental system consisted of eighteen 75-L tanks supported by a recirculating seawater system in an indoor, climate-controlled laboratory. Juveniles (average weight = 7.1 g) were stocked at a density of 15 fish/tank (N = 3 tanks/treatment) and were fed the test diets daily to apparent satiation for 55 days. ResultReplacement of FM protein with TM protein caused slight declines in dietary amino acid concentrations (notably arginine, methionine, and tryptophan) at higher replacement levels. At terminal sampling, no significant differences in survival (87-96%), percent body weight gain (157-228%), feed conversion ratio (1.50-1.71), or proximate composition were observed among dietary treatment groups. However, significant positive linear trends were found between incremental levels of TM and final fish weight, body weight gain, and specific growth rate. Whole-body fatty acid composition reflected dietary levels. ConclusionResults indicate that TM protein can be used to replace at least 41.6% of the FM protein in the diet for juvenile Black Sea Bass without adverse effects on survival, growth, feed utilization, or whole-body proximate composition.