Juvenile bluegill ( Lepomis macrochirus ) can be fed diets without marine fish meal without adverse effects on growth, survival, diet utilization, and body composition

Abstract

There has been an increasing global demand for large bluegill (Lepomis macrochirus) to supply the food-fish market. Current bluegill diets resemble those for largemouth bass and contain a high percentage of marine fish meal (FM). Research into the use of alternative protein ingredients for bluegill diets need to be conducted to not only conserve finite marine resources, but to reduce cost and expand the supply of bluegill to the global market. We evaluated growth, survival and body composition of bluegill fed diets in which FM was partially or totally replaced by various combinations of soybean meal, poultry by-product meal, canola meal, soy protein concentrate, wheat gluten or a commercial protein blend (Pro-Cision™). Seven isonitrogenous (40% protein), isolipidic (11%) and isocaloric (17.1 kJ/g) diets were formulated to meet the known nutrient and energy requirements of largemouth bass and bluegill using centrarchid nutrient availability data for most of the dietary ingredients. One of the test diets consisted exclusively of plant protein sources. Juvenile bluegill (9.1 g initial weight) were reared in a recirculating aquaculture system (3 tanks/diet; 20 fish/tank) and fed the test diets once daily to satiation for 70-day. The test diets in which various percentages of SBM, PBM and/or a commercial protein-blended product (Pro-Cision) which completely replaced FM resulted in similar growth performance, feed efficiency and body composition of juvenile bluegill compared to fish fed diets containing 30% FM. However, as formulated, the all-plant diet resulted in reduced growth. Mean diet performance rankings based on response measures along with differences in essential nutrient and energy levels (i.e. amino acids, P and starch) provided some insight into subtle differences in performance among diets. It appears that bluegill can be fed fish meal-free diets without reduced production (growth) if animal-source protein ingredients (PBM or Pro-Cision) are added; however, as formulated in this feeding trial, an all-plant diet resulted in reduced growth. Further study on formulating all-plant diets for bluegill is warranted.