From Plant By-Products to Insects to Shrimp: A Pathway to Sustainable Aquaculture Feed in a Circular Economy

Shrimp aquaculture often has a large environmental footprint, partly due to the fish meal content of commercial shrimp feeds. One potential way to improve ecological sustainability would be to replace fish meal-based compounds in shrimp feeds with insect-based compounds, such as black soldier fly (BSF; Hermetia illucens s.l.) larvae reared on plant by-products. However, little is known about the effects of novel plant by-products on the growth characteristics of BSF larvae and how these in turn affect aquaculture species, including Pacific white shrimp (PWS; Penaeus vannamei). Therefore, the general goal of this study was to evaluate the suitability of BSF larvae reared on three common plant by-products (cocoa bean shells, depectinized apple pomace, and potato peelings) as a feed component for PWS aquaculture based on randomized controlled feeding trials. The study showed that both the nutritional profiles of the tested feeds and the profiles of the BSF larvae reared on these feeds differed, particularly in crude protein and crude fat content. All BSF larvae reared on the plant by-products showed significantly lower growth performance than those reared on a control feed, possibly due to the presence of toxins and insecticides, and a low content of some essential amino acids. However, no significant differences in growth parameters were found between PWS fed BSF larvae reared on plant by-products and the control feed. Possibly, BSF do not bioaccumulate the toxins/insecticides present in the plant by-products and/or partially compensate for amino acid deficiencies. PWS fed BSF larvae reared on plant by-products had feed conversion ratios (FCRs) ranging from 0.8 to 1.0. These excellent values may fully or partially compensate for the lower growth performance of the BSF larvae reared on these by-products. This study may be of economic importance for future shrimp aquaculture, confirming that BSF can be a central link in the transformation of low-cost plant by-products into high-quality protein sources for sustainable shrimp farming in a circular economy.