Introduction: The Persian sturgeon (Acipenser persicus Borodin, 1897) is one of the five species of sturgeon in the Caspian Sea. It is found in the Caspian Sea and the eastern Black Sea and migrates to specific rivers to spawn. Since it prefers warm waters, most of its populations are found near the coastal waters of the southern and southeastern Caspian Sea. Over the past decades, Persian sturgeon have been artificially propagated and fingerling have been released into the Caspian Sea to restore natural stocks. Given Persian sturgeon stocks, have been reported to be at high risk of extinction, its breeding can be a very effective contribution to preserving the stocks of this valuable species. The aim of the study was to determine the effect of feeding different diets on growth, survival, and activity of some digestive enzymes in Iranian carp larvae.

Material and Methods: The research was conducted with 7 treatments and 3 replications in each treatment in the Aquaculture Department of the International Sturgeon Research Institute. For this purpose, the number of 1050 Persian sturgeon (Acipenser persicus Borodin, 1897) larvae, resulting from natural male and female propagation, with an average initial weight of 0.076 ± 0.002 grams, were randomly released in 21 plastic round tanks with a total volume of 50 liters and 20 liters of water (100 larvae in each tank, 5 larvae per liter), in a flow-through system (0.5 liters per minute in each tank) for 30 days with different treatments (T) including: 1- Artemia nauplii+ chironomid larvae + formulated  diet (from the 1st day of rearing), 2- Artemia nauplii + chironomid larvae + formulated diet (from the 9th day of rearing), 3- Artemia nauplii + Artemia biomass + formulated diet (from the 1st day of rearing), 4- Artemia nauplii + Artemia biomass + formulated diet (from the 9th day of rearing), 5- Artemia nauplii + Artemia biomass + chironomid larvae + formulated diet (from the 1st day of rearing), 6- Artemia nauplii + Artemia biomass + chironomid larvae + formulated diet (from the 9th day of rearing) and 7- feeding only with formulated food from the beginning to the end of the period. The larvae were fed 12 times a day. 

Results and Discussion: The results showed that, the highest and lowest survival rate were in T2 and T7, respectively (p<0.05). T4 had the highest weight gain without statistically significant difference with T2, T5 and T6 (p>0.05).  The lowest increase in body weight was recorded in T7 (p<0.05). The activity of lipase and alpha-amylase enzymes in T2 was significantly higher than others T (p<0.05). Pepsin enzyme activity in most T, was significantly higher than T7 (p<0.05). The activity of trypsin enzymes in T4 was measured significantly more than others T (p < 0.05). Feeding larvae with feeding regime containing chironomid larvae (T2) + formulated diet (9 days after the start of the rearing period) caused a significant increase in survival compared to others T (p<0.05). Considering the importance of survival in fish larval rearing (Kumar Pradhan et al., 2014), it can be concluded that the presence of chironomid larvae had a significant effect on the survival of larvae, especially in T2. Overall, treatments 1, 2, 5, 6, 3, and 4 were preferred for feeding Persian sturgeon larvae, respectively. On the other hand, considering the high price of chironomid larvae and the difficulty of obtaining them, it can be stated, based on the results of the research, Artemia biomass can also result in acceptable survival and growth when used alone (T3 and T4) and in combination with chironomid larvae (T5 and T6). Considering the positive and effective role of using chironomid larvae in feeding sturgeon larvae (Ghorbani Vaghei et al., 2024; Efatpanah et al, 2024, Efatpanah et al., 2021), the limitations of its use (expensiveness and difficulties in obtaining) have led to Artemia biomass also having an acceptable place in feeding sturgeon larvae. Therefore, using Artemia biomass alone or in combination with chironomid larvae can lead to acceptable results (Ghorbani Vaghei et al., 2024). 

Conclusion: It can be concluded that changing the larval diet had a statistically significant effect on growth rate, survival rate, and enzyme activity in some treatments. At the end of the research period, feeding the larvae with chironomid larvae and Artemia biomass increased the survival rate and growth of the larvae. This indicated the positive role of chironomid larvae and Artemia biomass in this regard. The lowest survival was recorded in treatment 7. The presence of chironomid larvae and Artemia biomass in the larval feeding regimes, can lead to improved growth, survival, and enzyme activity of Persian sturgeon larvae. Despite the greater benefits of feeding with chironomid larvae, their high cost and difficulty in obtaining them, limit their use. However, the greater abundance of Artemia biomass and its much lower price compared to chironomid larvae have increased the tendency to use Artemia biomass alone or in combination with chironomid larvae to feed sturgeon larvae.