The drastic surge in Sardine landings in Korea underscores the urgent need for sustainable upcycling strategies. However, research on the feasibility of using sardine (SD) in food waste (FW)-based substrates during the cultivation of black soldier fly (Hermetia illucens) larvae (BSFL) remains limited. Thus, we aimed to investigate the effect of incorporating varying SD contents (0, 25, 50, 75, and 100%), into which 4-day-old (third-instar) larvae weighing approximately 0.02 g were introduced and reared for 12 days in triplicate. SD inclusion in the substrate had a dose-dependent effect on BSFL growth; higher concentrations (≥50%) markedly inhibited key growth indices, including a significant reduction in total biomass (p < 0.05). Incorporating SD into the diet dose-dependently enriched the biomass with eicosapentaenoic acid and docosahexaenoic acid while reducing the relative proportions of saturated and monounsaturated fatty acids (p < 0.05). Proteobacteria and Firmicutes were the dominant phyla in the intestinal microbiota of BSFL. Further, SD inclusion altered the gut microbial community structure. Increased SD concentration in the diet led to a progressive reduction in unique genera, indicating decreased microbial diversity at higher inclusion levels. Overall, incorporating SD into FW for BSFL cultivation is feasible; however, optimizing substrate composition—particularly moisture and nutrient balance—is necessary to enhance larval growth and productivity.

Groupers (Epinephelidae, Pisces: Perciformes) are a tropical and subtropical marine fish comprised of 16 genera and 163 species (Craig et al., 2011), and are commercially valuable in Asian live fish markets (FAO, 2017; Rimmer & Glamuzina, 2019). The sexual characteristics of Epinephelidae are complex and diverse and classified as gonochorism, protogynous hermaphroditism, and bi-directional sex change (Sadovy de Mitcheson & Liu, 2008; Liu et al., 2016).

Rochia nilotica is a tropical Pacific gastropod inhabiting shallow coral reef habitats and supporting important marine resources in Pacific island nations. In this study, we analyzed specimens collected from Weno Island, Chuuk Atoll, Federation States of Micronesia (FSM), using an integrative approach that combined morphological characteristics, molecular phylogenetics (COX1 and 16S rRNA), and complete mitochondrial genome analysis. While the Chuuk population exhibited morphological features consistent with R. nilotica, molecular data revealed substantial genetic divergence. Phylogenetic analyses based on the complete mitochondrial genome (17,664 bp) clustered the Chuuk specimen with Rochia virgata. Phylogenies inferred from concatenated COX1 and 16S rRNA gene sequences yielded congruent topologies, placing the Chuuk lineage within the Rochia clade but clearly separated from other R. nilotica populations in New Caledonia and Mo’orea Island, French Polynesia. This genetic divergence is likely driven by the long-term geographic isolation of Chuuk Atoll. The lagoon’s fringing reefs descend rapidly into waters exceeding 4000 m, which may act as a barrier to restricting larval dispersal. Combined with the extremely short planktonic larval duration of R. nilotica (approximately four days), such environmental isolation may promote the formation of a distinct gene pool. Despite morphological uniformity, the observed genetic divergence suggests that the Chuuk population may represent a cryptic species. Our study provides a complete mitochondrial genome and offers robust phylogenetic framework that provides an understanding of species boundaries within Rochia. These findings underscore the importance of integrating genomic and morphological data for accurate species identification and have implications for conservation and sustainable aquaculture practices in geographically isolated reef ecosystems.

This study evaluated the optimal dietary lipid level for Atlantic salmon (Salmo salar) reared in freshwater, aiming to provide foundational knowledge for the development of cost-effective and nutritionally balanced aquafeeds. Four experimental diets were formulated to contain comparable crude protein levels (47%) but graded lipid levels of 14% (L14), 16% (L16), 18% (L18), and 20% (L20), and were fed to salmon with an initial mean body weight of 241.5 ± 9.7 g during a 12-week feeding trial. Fish in the L16 group exhibited the highest weight gain (WG) and feed efficiency (FE), whereas those in the L14 group showed significantly reduced growth performance. Antioxidant analysis revealed that glutathione peroxidase (GPx) activity was lowest in the L14 group (p < 0.05), while plasma glucose concentration was minimized in the L16 group (p < 0.05). Transcriptomic profiling of liver tissue from the L14 and L16 groups identified 2117 differentially expressed genes (DEGs). Genes associated with lipid metabolism were more highly expressed in the L16 group, whereas immune- and inflammation-related genes were upregulated in the L14 group. These findings suggest that a dietary lipid level of approximately 16% is most favorable for promoting growth, metabolic stability, and overall health in freshwater-reared Atlantic salmon, thereby providing practical guidance for optimizing feed formulation and improving the economic efficiency of freshwater salmon aquaculture.