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Morphometric indices and color traits of Malawian cichlid zebra (Pseudotropheus zebra) fed conventional diets and (Hermetia illucens) substituted fish meal diets
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Somayye Mohamad Ali-Khani1   , Rezvan Mousavi Nadushan2 * |
1- Department of Marine and Fisheries Sciences, Faculty of Natural Resources and Environment, Science and Research Branch, Islamic Azad University Tehran, Iran
2-Department of Marine and Fisheries Sciences, Faculty of Natural Resources and Environment, North Tehran College, Islamic Azad University Tehran, Iran , mousavi.nadushan@gmail.com |
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Abstract: (123 Views) |
Introduction: In recent years, there has been an observable rising trend in using insect protein as an alternative protein source in aquafeed formulations. Estimates indicate that the long-term use of fish meal for aquafeed is not sustainable, and global fish meal production continues to decline. On the other hand, researches show that insects can be farmed sustainably and economically in small spaces with minimal water consumption. It has also been shown that insect protein can be partially or fully replaced in diets for crustaceans and farmed fish without reducing growth performance, feed conversion efficiency, intestinal health, immunity, or muscle quality, and some formulations even improve these parameters (Wang et al., 2025). Among insect-derived proteins, black soldier fly (Hermetia illucens) larval protein is particularly promising for aquafeed applications. Black soldier fly represent a developmental stage with strong potential to substitute fish meal as a cost-effective, nutrient-dense protein source for aquaculture feeds. Consequently, BSF-L may help displace the costly, limited fish meal supply, supporting higher production and a more sustainable industry to meet the rising global demand for fish products (Su et al., 2025).
Materials and Methods: In this study, conducted over 8 weeks, the effects of replacing fish meal with black soldier fly larva meal (H. illucens) on growth, weight-length relationship, and condition factor in Malawi cichlid fish Pseudotropheus zebra were examined. The initial average weight was 0.28 ± 0.02 g. The fish were randomly divided into five groups, each containing 30 fish, and five feeding treatments were established, each with three replicates. Fish were fed four times daily, and diets in the feeding treatments contained 0% (control), 10%, 30%, and 50% black soldier fly larva meal powder. At the start and at weekly intervals after the start and at the end of the trial, growth parameters including weight and total length were measured.
Results and Discussion: The highest weight (164.7 ± 2.1 g) was observed in the 50% larva meal group compared to the control group (101 ± 1.7 g). The welfare of the experimental fish was also evaluated through the condition factor, body condition factor did not differ significantly between the control group and those fed diets containing 10% and 75% larva meal powder; however, in fish fed the 25 and 50% larva meal diet, the condition factor showed the highest and statistically significant values (1.37 and 1.43), suggesting that all the fish were in good health (Limbu et al., 2022). Additionally, a least-squares regression of the base-10 logarithm of weight against the base-10 logarithm of total length yielded an equation of W = 2.9343 × log10(TL) − 1.2047 (R² = 0.9853) for the 50% larva meal diet, versus W = 1.8043 × log10(TL) + 0.1029 (R² = 0.9764) for the control group. Growth of P. zebra across the five feeding treatments followed a negatively allometric pattern. From this research, the allometric coefficient b was found to range from 1.8043 to 2.9343, indicating a predominantly negative allometry with a tendency toward isometric growth in fish fed a diet containing 50% black soldier fly larva meal (Odhiambo et al., 2023). Colorimetric parameters (a*, b*, and L*) in the 50% and 75% larva meal groups differed from the control. The highest color scores were observed in fish fed the 50% and 75% diets. Although there are no studies specifically addressing the effects of animal-protein–based diets on fish skin coloration, diets containing black soldier fly larva meal appear to have a considerable coloring capacity, enhancing color attractiveness, particularly brightness, in P. zebra, similar to Sparus aurata (Pulcini et al., 2020).
Conclusion: The results of this study indicate that replacing fish meal with black soldier fly larva meal powder in the diet of Pseudotropheus zebra produced a significant difference in the condition index, especially in the 50% treatment. This finding suggests that the optimal proportion of this powder in the diet can have a substantial positive impact on the physiological status and growth of the fish. It was also found that in this treatment, growth was balanced and proportional, with simultaneous increases in length and weight, reflecting the positive effect of the protein components in the larva meal powder on the growth process. Once more, linear models adequately fit the experimental data, with R² values for all treatments exceeding 0.9 (ranging from 0.97 to 0.98), indicating a very good match between the mathematical models and the data. The study also showed that consuming 50% larva meal powder had a significant positive effect on color parameters, especially blue color, in the cichlid fish, with enhanced synthesis, absorption, and storage of all pigments following larva meal powder consumption, leading to increased brightness and color appeal. |
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| Keywords: black soldier fly larvae, growth, color, Malawian cichlid fish |
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Type of Study: Research |
Subject:
Special
Received: 2025/09/13 | Accepted: 2025/12/12
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