Facing the challenge of discarded fish: improving nutritional quality of two insect species larvae for use as feed and food

Abstract

Fishery discards represent 10% of total fishery catches, and insect rearing can be accomplished using this wasted resource. Considering that fish are the main source of n-3 very long-chain polyunsaturated fatty acids for human nutrition, and that fish contain both eicosapentaenoic acid and docosahexaenoic acid, this study focused on monitoring the accumulation of such n-3 very long-chain polyunsaturated fatty acids in insect larvae. To determine the feasibility of this process, we monitored nutritional changes achieved in two insect larvae – black soldier fly (Hermetia illucens Linnaeus, 1758) and mealworm (Tenebrio molitor Linnaeus, 1758) – fed using two different fish species from discards, i.e. round sardinella (Sardinella aurita Valenciennes, 1847) and blackspot seabream (Pagellus bogaraveo, Brünnich, 1768). Five different diets were prepared: control (broiler feed), 50% discarded fish (round sardinella and blackspot seabream) +50% broiler feed, and 100% discarded fish. The 100% blackspot seabream fed H. illucens accumulated eicosapentaenoic acid and docosahexaenoic acid up to 2.4 g /100 g and 0.8 g /100 g, respectively. T. molitor accumulated lower amounts of both n-3 very long-chain polyunsaturated fatty acids due to the low intake of fish-containing feed by the larvae.