Zabihollah Pajand

This study evaluated the nutritional quality of Hediste diversicolor cultivated using waste from beluga sturgeon ( Huso huso ) aquaculture. Over a 60-day trial, polychaetes were reared at four stocking densities (1000–7500 individuals per square meter (ind./m²)) and fed either commercial sturgeon feed or processed farming waste. Results demonstrated that sturgeon waste effectively supported polychaete culture, with survival rates ranging from 53% to 80%. However, worms fed commercial feed exhibited superior growth, yielding over three times greater biomass than waste-fed groups. Nutritional composition was significantly affected by both diet and density. Worms fed commercial feed at an intermediate density (2500 ind./m²) achieved the highest protein content (9.23%) and most beneficial fatty acid profile, characterized by a high PUFA content (46.85%) and n-3/n-6 ratio (0.39). While waste-fed worms showed reduced nutritional quality, an intermediate density of 2500 ind./m² also optimized their composition. A comparative analysis confirmed the commercial feed was richer in protein and essential fatty acids (EPA + DHA) than the processed waste. The study confirms the viability of using sturgeon waste to produce polychaete biomass for aquaculture. However, nutritional trade-offs suggest supplemental feeding may be required to achieve premium quality for aquaculture feed, providing critical benchmarks for implementing circular economy principles in aquaculture systems.

Six different feeding regimes (FR) were tested from 7 to 38 days post hatching (dph). Five thousand four hundred larvae (7 dph, 0.048 g) were randomly stocked in 18 fiberglass tanks contained 100 L fresh water (300 larvae per each tank). In larvae fed with FR-B, includes Artemia nauplii (AN) + Artemia biomass (AB) + microdiet (MD), the body weight (BW) at the end of trail (38 dph) similar the FR-D (AN + CHL + AB + MD), and E (AN + CHL + AB), was at high level. Survival rate was higher in larvae fed FR-A includes AN + chironomid larvae (CHL) + MD, but had a lower BW ( ). Moderate BW and survival rate were detected in larvae fed FR-C (AN + DP + MD). Larvae fed only MD (FR-F), had the lowest survival and the highest BW ( ). Different FR had a significant effect on crude protein (CP), crude fat (CF), ash, and dry weight ( ). The larvae fed FR-C and D had the highest CP ( ). The highest CF and ash in larvae were detected in FR-F and C, respectively ( ). Larvae from FR-A and B had higher levels of n−3 long chain polyunsaturated fatty acids in comparison with others FR ( ). The use of AB and CHL can increased the weight and survival rate of larvae, respectively. At the end of trail, the activity of pepsin, trypsin, lipase and α-amylase enzyme levels were lower in FR-B and F than others FR. Totally, by using a combination of AN + CHL + AB + MD had better results than others and ordered to H. huso larvae feeding. Using MD alone, can cause lesser development of the digestive system and little attractiveness, therefore it can cause starvation, and the empty digestive tract of larvae.

Thiamine is a crucial nutrient in larval stage of fish, and thus, the present study aimed at evaluating the effects of dietary thiamine supplementation on survival, growth performance, and biochemical parameters of beluga, Huso huso, larvae. The fish larvae (50 ± 4.5 mg) were fed diets containing 0 (control), 5, 10, and 20 mg/kg thiamine for 26 days from 18 days after hatching to 44 days after hatching. Thiamine significantly increased the larvae survival, growth rate, digestive enzymes activity, and whole body protein and ash but decreased the whole body lipid and moisture ). Also, alanine amino transferase (ALT) and alkaline phosphatase (ALP) were decreased significantly in thiamine-treated groups ( ). The highest survival and whole body ash were observed in 20 mg/kg thiamine treatment; the highest whole body protein and lipase activity were observed in 10 mg/kg thiamine treatment. The highest growth rate, amylase, and lowest whole body lipid, alanine amino transferase (ALT), and alkaline phosphatase (ALP) were observed in 10 and 20 mg/kg thiamine treatments. All thiamine-treated fish exhibited similar pepsin and chymotrypsin activities, all above the control fish. There were no significant effects of dietary thiamine supplementation on trypsin, whole body lysozyme, alternative complement (ACH50), lactate dehydrogenase (LDH) activities, and IgM levels. According to the results, 10–20 mg/kg dietary thiamine supplementation can increase the performance of beluga larvae by improving the health of liver and the activity of digestive system.