Introduction: Protein is among the most essential and effective nutritional resources for the growth of farmed aquatic species. However, protein sources are limited because they are predominantly produced from marine pelagic fishes, and excessive use of fish meal not only can lead to negative environmental consequences but also, due to unstable supply, has been economically less efficient and has driven price increases over recent decades. Therefore, research on the use of alternative protein sources with higher availability, digestibility, and efficiency to replace fish meal and in line with the sustainable development of aquaculture is essential. Then again, in aquaculture research, growth models based on mathematical equations are widely used to describe growth patterns and to estimate fish weight at sampling intervals. Accurate estimates of live mass and, consequently, the amount and nutritional quality of feed required are critical for effective aquaculture management. Furthermore, understanding the relationships between body weight and its composition informs trait selection and guides efforts toward selective breeding and genetic improvement in aquaculture. An accurate length–weight equation enables the conversion of growth in length to weight in stock assessment and biomass evaluation models, and it makes it possible to estimate live biomass from length-frequency distributions, condition, and morphometric characteristics of fish populations. Therefore, the length–weight relationship is an important and efficient tool in aquaculture management.
Materials and Methods: In this study, the effect of feeding and fish hydrolyzed protein (FPH) supplementation on the length-weight relationship, growth pattern, and condition factor in giant sturgeon (Huso huso) was investigated. A total of 300 fish with an average weight of 45 ± 5 grams were released into 9 circular ponds with a diameter of 2 meters. During the 40-day experiment, the fish were fed three iso-protein diets, including a control diet (without supplementation), a diet containing 5% FPH, and a diet containing 10% FPH. During the experimental period, every 10 days, fish samples were selected to measure length and weight. At the end of the experiment, from each replication, three fish were randomly chosen, and whole-body composition was determined by measuring protein, fat, moisture, and ash contents. To determine and compute the length–weight relationship for the experimental treatment populations, total length and weight were first log-transformed (log10), and the linear regression analysis of log10(W) on log10(TL) was performed. The resulting length–weight regression equation for each group of fish in the experimental treatments was then fitted, and regression slope and intercept were used to obtain length-weight relationships and mean condition factor values (Engebretsen et al., 2024)
Results and Discussion: The weight of fish in the 5% FPH treatment (average weight 351.66 ± 30.34 grams) and the 10% FPH treatment (316.13 ± 30.99 grams) showed an increasing trend compared to the control treatment (304.53 ± 30.83 grams). The length-weight relationship based on the equation W = aL^b showed for the control fish W = 0.05L^2.46, for the fish in the 5% FPH feeding treatment W = 0.05L^2.89, and for the fish in the 10% FPH feeding treatment W = 0.05L^2.50. Substantively, the average condition factor for the control fish was 0.40 ± 0.06; for fish fed with 5% FPH supplementation, it was 0.59 ± 0.02; and for fish fed with 10% FPH supplementation, it was 0.48 ± 0.03. The results of this study indicated that growth in beluga sturgeon was negatively allometric, with the growth rate in length being significantly higher than that in weight. Additionally, FPH protein supplementation influenced the growth coefficient (b), with the highest weights for specific lengths obtained in the 5% supplementation treatment. Finally, the results of the one-way ANOVA test showed that the difference in the average condition factor among the groups of fish in the experimental treatments was significant (p<0.01). Researchers attribute improvements in fish performance to factors such as enhanced protein digestibility arising from the degree of hydrolysis of the feed or the impact of absorbing free amino acids released during hydrolysis. Currently, and globally, most studies in aquaculture have focused on free amino acids, including analyses and the use of the condition factor as a metric of growth and an indicator of nutritional status. However, the present study provides only baseline data on the condition factor for the obesity of the sturgeon species.
Conclusion: The hydrolyzed protein is a source of proteins, amino acids, and bioactive peptides, and its use as a supplement will have significant and promising effects in nutrition and aquaculture. The present study also showed that there is a high potential for using diets based on partial replacement of hydrolyzed protein in the nutrition of beluga larvae. Also, the amount of hydrolyzed protein replacement can be a key factor in formulating sustainable and effective diets for the early life stages of giant sturgeon. Finally, by replacing 5% of hydrolyzed protein in the diet, significant and positive effects were achieved on carcass quality, condition factor, and morphometric components of Huso huso larvae. |
