Study of effect of nereis diversicolor in growth and survival of Acipenser persicus larvae

The present research aimed to study effect of Nereis worm in feeding, growth, survival and carcass biochimical compositions of persian sturgeon larvae. Five diets including zooplankton (100%) as the control (Z), Nereis diversicolor worm (100%), a mix of Nereis and zooplankton (50% for each), a mix of Nereis, zooplankton and concentrate food (33% for each) with 3 replicates were established. At first, Nereis worms were cultured up to the weight of 200 mg according to the protocol done in the International Sturgeon Research Institute. Required zooplanktons were obtained for Dr. Beheshti Sturgeon Rearing and propagation center. Concentrate food was also made in the ISRI. Persian sturgeon larvae with the average weight of 95.66 mg were put in 60-Liter tank (60 larvae in each tank) under the same physical and chemical parameters of water. 8 days after the beginning of active feeding, they were fed five times a day with experimental dites based on 20-30% of their weight for 15 days. Water quality parameters, such as dissolved oxygen, temperature, pH values were recorded daily. The average of temperature, pH and dissolved oxygen during the test were 22.8±1.3ºc, 7.5±0.1 and 6.58±0.9 mg/l respectively. At the end of this period, condition factor (k), specific growth rate (SGR), food conversion rate (FCR), weight gain (WG) and Body weight index (BWI) were calculated. Total fat and fatty acids profile were analyzed. The results showed that there was a significant difference between growth indexes and food consumption (p<0.05). BWI, GR and SGR indices showed no significant difference between N and NZ treatment, but the average of these indices were higher in NZ treatment. The most and the least average of SGR, BWI were observed in NZ and NZC treatments respectively. Condition factor showed no significant difference in all diets except NZ. FCR had no significant difference between N and NZ as well as after diets. The highest and the lowest survival rate was observed in N treatment (96.11±1.46%) and NZC (85.55±3.37%) respectively. The results of carcass analysis showed that there is a strong correlation between fatty acids of body and fat resources of diets. According to the significant difference in growth rate between treatments (p<0.05), the larvae fed with N diet presented a better performance compared with others. These results indicate that cultured sturgeon larvae need n-3 and n-6 series of fatty acids in their diet.