Environmentally sustainable feeding system for sea trout (Salmo trutta m. trutta): Live food and insect meal-based diets in larval rearing

Abstract Wild salmonid populations are successively decreasing due to environmental changes caused by excessive human activity or climate change. Thus, effective breeding and rearing programs are required that focus on nutritional strategies, including feeding behaviour and starter feeds composed of environmentally sustainable ingredients. In this study, a combined feeding system that included the addition of live food (Artemia salina for 0, 3 or 7 days), test diets (containing insect meals) and the control diet (fishmeal-based) was assessed. Two types of insect meals were used, with one from the larval stage of insects (mealworm and black soldier fly) and the other from the imago stage of insects (Turkestan cockroach and tropical house cricket). The study was carried out on sea trout (Salmo trutta m. trutta) larvae, and the fish growth performance, survival and condition were evaluated during a 60-day feeding trial. Fish body weight, length and condition (CF) were similar in the groups fed the control diet and the groups fed the larval stages of insects. The feed conversion ratio (FCR) was comparable in all treatments. The highest weight gain (WG), specific growth rate (SGR) and survival rate (SR) were observed in the fish fed the diet that included larval insect meal. The application of live food did not significantly affect the rearing results, although the type of insect meal had a crucial impact on fish rearing. In summary, diets containing 20 % insect meal from the larval stage may be used as an effective feed component for juvenile fish.