Insect meal is gaining increased attention in aquafeed formulations due to high protein content and an essential amino acid profile similar to that of fishmeal. To investigate insect meal in feed for European perch Perca fluviatilis, a promising candidate for European intensive culture, we replaced standard fishmeal with partially defatted black soldier fly Hermetia illucens larva meal at rates of 0%, 20%, 40% and 60% (groups CON, H20, H40 and H60, respectively) and compared growth performance, somatic indices, hematological parameters, whole-body proximate composition and occurrence of spleen lipidosis. In addition, we assessed the economic and environmental sustainability of the tested feeds by calculating economic conversion ratio (ECR) and economic profit index (EPI). The tested groups did not differ in survival rate. Significant differences were documented in final body weight and specific growth rate, with the highest values in CON, H20 and H40. The proximate composition of fish whole-body at the end of the experiment did not differ in dry matter, crude protein or ether extract, while organic matter, ash and gross energy composition showed significant differences. The fatty acid content and n-3/n-6 ratio showed a decreasing trend with increasing H. illucens larva meal inclusion. No differences were found in hematological parameters among tested groups. The H. illucens larva meal inclusion significantly affected ECR and EPI, even at 20% inclusion level the cost of diets did not differ from the control fish meal based diet. Results suggested that 40% inclusion of H. illucens larva meal can be used successfully in standard diets for perch.

The present work employed a systematic review and meta‐analysis to quantify the overall effects of various types of insect meal on special growth rate (SGR), feed conversion ratio (FCR) and protein efficiency ratio (PER) of aquatic animals. A total of 107 studies published from 1990 to 2021, targeting 23 freshwater and 17 marine fish species, employing 17 insect species as a replacement for fishmeal, was compiled. Overall, a significantly higher Hedges’ g value for SGR and lower FCR was found in aquatic animals fed dietary larval defatted mealworm Tenebrio molitor and pupal full‐fat silkworm Bombyx mori compared with fishmeal diet. The majority of dietary insect meals had a negative linear correlation with Hedges’ g of growth performance, except larval fly Chrysomya megacephala, which had a positive linear relationship, and of prepupal defatted black soldier fly Hermetia illucens, which had a negative quadratic relationship. Some insect meals, including G. bimaculatus, adult grasshoppers of Oxya fuscovittata and Zonocerus variegatus and larval full‐fat Cirina butyrospermi, supported adequate growth of aquatic animals at plausible inclusion levels. At as low as 2.2%, insect‐derived chitin supported growth performance and improved feed utilization of marine fish species. In the quest to minimize fishmeal in aquafeeds, insect meal holds enormous potential but is not the sole option; rather, integrating insect meal and novel/conventional materials is more strategic. The present study lays the groundwork for further multidisciplinary considerations for the effective use of insect meal as an alternative aquafeed protein with the goal of long‐term sustainability.

The study investigated the combined effect of weaning from live feed to a commercial dry pellet at 10, 15, 20, 25 or 30 days posthatching (dph) and co‐feeding for 1, 3 or 6 days on survival and growth of Coregonus peled larvae. Additional groups fed only live Artemia sp. nauplii (ART), and only Biomar LARVIVA ProWean 100 (DRY) were included. A final survival rate of 66.4%–85.5% was observed in groups weaned after 20 dph. Final body weight (BW) and total length (TL) were significantly lower in groups weaned at 10 and 15 dph, regardless of the duration of co‐feeding. Larvae reached 29–37 mg BW and TL of 17.7–19.0 mm in groups weaned at 20, 25 and 30 dph. The recommended minimum duration of feeding with live food, based on these results, is 20 days. Based on the significantly higher yield of larvae weaned after 20 dph irrespective of co‐feeding duration, it can be concluded that abrupt weaning to dry food after 20 days of feeding with live prey can provide adequate production while reducing the effort and costs associated with live feed.

In the present study, a possible nature immunostimulant and growth promoter—humic substances (HS) originating from Siberian leonardite mineraloid—were tested on juvenile Clarias gariepinus performance. Feed additive was applied onto commercial pelleted feed at four HS levels—0, 1, 3, and 6% w/w (HS0, HS1, HS3, HS6, respectively). Diets were tested in five repetitions (in total, n = 1800 individuals, mean body weight 28.1 ± 6.2 g) for 56 days. Growth and production parameters, fish condition and somatic indices, and overall mortality were evaluated after 14, 28, 42, and 56 days of exposure. Whereas, plasma samples were collected only after 0, 28, and 56 days, when fish health status was assessed with biochemical parameters (total proteins, TP; alanine aminotransferase, ALT; aspartate aminotransferase, AST; lactate dehydrogenase, LDH; cholesterol, CHOL; triglycerides, TAG) and fish antioxidant status with glutathione (reduced glutathione, GSH; oxidized glutathione, GSSG; glutathione ratio GSH/GSSG). Although a significantly positive effect of HS feed additive on growth performance was not found in the present study, moderately positive effects were found regarding biochemical parameters (ALT, AST, LDH, CHOL, and TAG) and antioxidants (GSH/GSSG ratio) that were improved especially in the HS3 group.

The supplementation of fish diets with phytogenics can increase growth performance and can modulate immune system response. European perch Perca fluviatilis (initial weight 25.0 ± 0.4 g) were fed a diet including 0 (Control), 10 (G10), 20 (G20), and 30 (G30) g kg−1 garlic powder. No significant difference in the growth parameters and somatic indices were observed. Significantly higher fat digestibility was observed in G10 and G30 diets compared to in the control and G20 diets(p < 0.05). Significantly greater red blood cell and white blood cell counts were observed with the G10 diet (p < 0.05). Garlic significantly decreased serum cholesterol in all of the experimental groups. Serum albumin was significantly higher in the G10 and G20 diets (p < 0.05). Immediately after the overcrowding stress challenge, the garlic groups showed significantly higher cortisol levels than the control group, while no significant difference was observed in the glucose concentration among groups. At 1 h post-stress, all of the groups that had been fed a garlic-supplemented diet showed lower cortisol levels than the control group, and this trend was maintained at 6 and 24 h post stress (p < 0.05), and glucose level in all garlic groups was significantly lower than control (p < 0.05). Garlic at 10 g kg−1 in feed can improve apparent fat digestibility and selected blood parameters and can enhance resistance against high-density and net handling stress in Eurasian perch.

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Early life history of Clarias gariepinus from egg fertilization to full yolk sac resorption was studied at 33 temperatures within the thermal range 17.4-35.6°C. The viable temperature range for embryonic development; temperature at which ontogeny is hypothetically arrested (15.4°C); viable temperature range for larval development; and the number of effective day-degrees for the embryonic and larval periods were determined. The early life history of C. gariepinus was found to be temperature-dependent in terms of the onset of key ontogenetic events, developmental rate, survival rate, and size of larvae. The length of the incubation period, hatching period, size of larvae at hatching, time to first intake of exogenous food, and time to full yolk sac resorption with and without exogenous feed supply, were inversely proportional to the temperature within the optimal temperature range. In terms of survival, the zone of thermal tolerance for early life history of C. gariepinus ranged from 18.9 to 33.2°C with the thermal optimum from 22.9 to 30.3°C, typical for thermophilous species. Temperature ranges of 20.6-22.9°C and 30.2-33.2°C were found to be suboptimal. Temperatures below 17.5 and above 35.1°C may be considered lethal during the embryonic period, and those below 18.9 and above 33.2°C are lethal during the larval period.