The expansion of the aquaculture sector requires diversification of feed ingredients. For example, using i nsects that have the advantage of a high protein content and suitable amino acid composition and can be farmed using side-stream from agro-industrial activities. T he large species diversity of insects e ach with their own unique nutrient profile, provides a plural of candidates that may allow to use a combination of species to better match the nutrient profile for the requirements of farmed the fish (“mix” of species) . H owever, studies into the use of insect mixes remain rare . W hile some studies have confirmed that replacement with single insect species could fulfill the fish nutritional requirements for growth, and digestibility, less attention has been paid to other important physiological parameters, including parameters critical for fish health and welfare. For example, during challenging periods such as the freshwater (FW)–seawater (SW) transition and associated smoltification process in salmon, which often results in elevated mortality on farms. I n this study , we evaluated how Atlantic salmon (Salmo salar) stress responses and osmoregulatory capacities functions were affected by the when substituting soy protein concentrate (SPC) with different inclusions of novel mix of insect meals (IM) and oil (IO) [black soldier fly larvae (Hermetia illucens) and yellow mealworm (Tenebrio molitor) ]. This feed trial included 10 weeks in FW and transfer of the smolts to SW for 6 weeks. A t the end of both FW and SW phases, fish were subjected to acute stress to monitor their ability to mount a normal stress response. Plasma levels of cortisol, ions, and selected metabolites were quantified as well as the e xpression of stress-associated genes, branchial osmoregulation, and brain neural plasticity.
Our results showed that inclusion of insect mix did not affect growth of the fish but resulted a dose-dependent effect on stress and osmoregulatory functions (Fig. 1), especially in SW , suggesting li fecycle specific differences. This study is the first in Atlantic salmon where the effect of a mixture of insects on welfare indicators is addressed in both FW and SW.
Acknowledgments: Fund ed by EEA InFishMix-PT-INNOVATION-0094 . Analysis performed in FBA-NORCE high throughput state of the art lab (SacLab). Fish trial performed in LetSea experimental and research center.