Partially Defatted Hermetia illucens Larva Meal in Diet of Eurasian Perch (Perca fluviatilis) Juveniles

SIMPLE SUMMARY: The replacement of fishmeal by insect meal is a promising strategy to obtain more sustainable fish feeds, a major goal in aquaculture. Black soldier fly Hermetia illucens larva meal has a high crude protein and fat content, essential for omnivorous and carnivorous fish. We used partially defatted H. illucens larva meal as a substitute for 20%, 40% and 60% of the fishmeal in standard diets for Eurasian perch and measured its effect on growth performance, feed utilization, body indices, fish body composition and blood indices. We found no significant differences in survival, size heterogeneity, hematology indices; or in whole-body dry matter, crude protein and ether extract content. The 60% inclusion reduced final body weight, specific growth rate, feeding rate, protein efficiency ratio, condition factor and hepatosomatic index. The fish-in-fish-out index decreased proportionally with increased H. illucens meal inclusion. Partially defatted H. illucens larva meal seems to be a promising alternative to fishmeal for Eurasian perch nutrition at moderate inclusion level. ABSTRACT: Insect meal is gaining increased attention in aquafeed formulations due to high protein content and an essential amino acid profile similar to that of fishmeal. To investigate insect meal in feed for European perch Perca fluviatilis, a promising candidate for European intensive culture, we replaced standard fishmeal with partially defatted black soldier fly Hermetia illucens larva meal at rates of 0%, 20%, 40% and 60% (groups CON, H20, H40 and H60, respectively) and compared growth performance, somatic indices, hematological parameters, whole-body proximate composition and occurrence of spleen lipidosis. In addition, we assessed the economic and environmental sustainability of the tested feeds by calculating economic conversion ratio (ECR) and economic profit index (EPI). The tested groups did not differ in survival rate. Significant differences were documented in final body weight and specific growth rate, with the highest values in CON, H20 and H40. The proximate composition of fish whole-body at the end of the experiment did not differ in dry matter, crude protein or ether extract, while organic matter, ash and gross energy composition showed significant differences. The fatty acid content and n-3/n-6 ratio showed a decreasing trend with increasing H. illucens larva meal inclusion. No differences were found in hematological parameters among tested groups. The H. illucens larva meal inclusion significantly affected ECR and EPI, even at 20% inclusion level the cost of diets did not differ from the control fish meal based diet. Results suggested that 40% inclusion of H. illucens larva meal can be used successfully in standard diets for perch.