Substrate Protein Enrichment of Black Soldier Fly ( Hermetia illucens ) Larvae for Diets of Olive Flounder ( Paralichthys olivaceus )

Continued growth of the aquaculture industry requires the identification of novel, cost‐effective protein sources. In this study, we evaluated the potential of black soldier fly ( Hermetia illucens ) larvae (BSFL) reared on protein‐enriched food waste (FW) as an alternative to conventional feed ingredients. In a 12‐days rearing trial, 8‐day‐old BSFL were randomly assigned to three dietary groups: FW alone (CBSFL), FW supplemented with soybean meal (SBM) (SBSFL), or FW supplemented with fish meal (FM) (FBSFL). The larvae were subsequently incorporated into diets for olive flounder ( Paralichthys olivaceus ) in an 8‐week feeding trial to assess dietary efficacy. Larval growth performance was highest in the CBSFL group ( p < 0.05). However, crude protein content was significantly higher in SBSFL and FBSFL than in CBSFL, confirming that the rearing substrate directly influences larval nutritional composition. In the 8‐week feeding trial, inclusion of BSFL derived from CBSFL and SBSFL substrates in olive flounder diets did not significantly affect growth performance compared with the control. However, it significantly increased lauric acid and total saturated fatty acid (SFA) content and decreased docosahexaenoic acid (DHA) content. These results reveal that BSFL can serve as an effective protein substitute in olive flounder diets, although a trade‐off exists between productivity and nutritional enrichment. Future studies should focus on optimising substrates and processing technologies to maintain larval productivity while enhancing the nutritional quality (especially the fatty acid profile) of farmed fish.