The aquafeed industry increasingly relies on using sustainable and appropriate protein sources to ensure the long-term sustainability and financial viability of intensive aquaculture. Yeast has emerged as a viable substitute protein source in the aquaculture sector due to its potential as a nutritional supplement. A substantial body of evidence exists to suggest that yeast has the potential to act as an effective immune-stimulating agent for a range of aquaculture fish species. Furthermore, the incorporation of yeast supplements and feed additives has the potential to bolster disease prevention, development, and production within the aquaculture sector. Except for methionine, lysine, arginine, and phenylalanine, which are typically the limiting essential amino acids in various fish species, the various yeast species exhibit amino acid profiles that are advantageous when compared to fishmeal. The present review considers the potential nutritional suitability of several yeast species for fish, with particular attention to the various applications of yeast in aquaculture nutrition. The findings of this study indicate that the inclusion of yeast in the diet resulted in the most favorable outcomes, with improvements observed in the overall health, growth performance, and nutritional condition of the fish. Digestibility, a key factor in sustainable feed development, is discussed in special detail. Additionally, this review addresses the utilization of yeast as an immunostimulating agent for fish and its digestion in fish. Furthermore, the research emphasizes the necessity of large-scale production of yeast as a substitute for fishmeal in aquaculture.

A 25-week experiment was undertaken to explore the effect of partial replacement of dietary fishmeal (FM) with black soldier fly meal (Hermetia illucens) (BS), mealworm meal (Tenebrio molitor) (MW), and a 1 : 1 mixture of both insect meals (BSMW) on fillet quality in African catfish (Clarias gariepinus). A total of 96 fish with an average initial body weight of 248 ± 28 g were stocked into a recirculating aquaculture system and fed in four different dietary groups (control, BS, MW, and BSMW). No mortality was recorded in any of the groups. At the end of the feeding period, 24 fish (n = 6 for each treatment, weight between 690 and 822 g) were used for analysis. There was no alteration in filleting yield or other slaughter indices within experimental groups, except the hepatosomatic index. Among quality attributes, pH 24 hr postmortem exhibited a significant difference ( ). In respect of the fatty acid profile, the n-6/n-3 ratio ranged between 1.17 and 1.40 but was not significantly modified by the partial replacement of FM. Similarly, the proximate composition of the fillets was not significantly different between the control and experimental diet groups. The ratio of polyunsaturated fatty acid to saturated fatty acids ranged between 0.67 and 0.79 in the fillets, without significant differences between groups. The atherogenic index was increased in the BS group, as compared to the others; however, the thrombogenicity index of fillets was not significantly affected. Similarly, the conventional quality traits of the fillet, such as cooking, drip, and thawing losses, did not differ within treatments. This study demonstrates that the dietary inclusion of black soldier fly and/or mealworm meals used for African catfish at the tested inclusion level has negligible impact on fillet properties.

A six-week experiment was carried out to test the effects of total (100%) and partial (50%) replacement of fish meal in the diet of African catfish growers with black soldier fly (B) meal, yellow mealworm (M) meal, and a 1:1 combination of both (BM) on the production and health of fish. A total of 420 fish with an average initial body weight of 200 ± 0.5 g were randomly distributed in triplicate to seven diet groups (C, B50, B100, M50, M100, BM50, and BM100, respectively). The growth performance and feed utilization of fish fed with partial or total replacement levels of FM with B were not significantly affected (p > 0.05) during the 6 weeks of feeding. In contrast, significant differences were observed between the groups fed with a diet where FM was totally replaced with M meal and the control in terms of final body weight, specific growth rate, feed conversion ratio, protein efficiency ratio, and protein productive value. Among the blood plasma biochemistry parameters, total cholesterol exhibited a significant difference (p = 0.007) between the M treatments and the control diet. The fatty acid profile of the liver was changed with respect to the long-chain polyunsaturated fatty acid content in all experimental groups. Parallel with this, the upregulation of elovl5 and fas genes in liver was found in all experimental groups compared to the control. Overall, this study shows that fish meal cannot be substituted with yellow mealworm meal in the practical diet of African catfish without compromising the growth, health and feed utilization parameters.

Most of the 27 species of sturgeons are endangered or close to extinction which is connected to habitat degradation, water pollution and overfishing. Conservation programmes are facing the problem of late maturation which can be reached between 5 and 11 years depending on the species and gender. The aim of our study was to investigate the possibility of shortening the sexual maturation using hormonal administration, and measure the blood serum hormone content to distinguish different genders and maturation stages. There was no effect of a 20-week-long hormonal treatment (10 mg carp pituitary/bodyweight kg/week) on the sexual maturation. The number of females was relatively high (67.6% n = 23) and the number of males was relatively low (11.8%, n = 4). Moreover, the number of hermaphroditic fish was surprisingly high (20.6%, n = 7) and appeared independently from hormone administration. Hermaphroditic fish had fully developed spermatozoa and could be distinguished by the increased level of testosterone hormone in blood serum.