Fish protein hydrolysate was produced from the viscera of yellowfin tuna (Thunnus albacares). Hydrolysis conditions (enzyme activity, temperature, and time) were optimized using response surface methodology. A factorial design was applied to minimize enzyme utilization and modeling of degree of hydrolysis (r 2 =0.94). Lack-of-fit test revealed a non-significant value for the model, indicating that the regression equation was adequate for predicting the degree of hydrolysis under any combination of the variables (P<0.05). The optimum conditions to reach the highest degree of hydrolysis were: 60.4°C, 90.25 min, and a protease (Alcalase 2.4 L) activity of 70.22 AU/kg protein.The spray-dried tuna visceral protein hydrolysates had relatively high protein (72.34%) and low lipid (1.43%) content. The chemical score of the hydrolysate indicated that it fulfils adult human nutritional requirements except for methionine. Lysine and methionine were the first and the second limiting amino acids in that order. Phenylalanine was the predominant amino acid in the hydrolysates with respect to common carp requirement. In addition, the protein efficiency ratio of tuna visceral hydrolysate was 2.85-5.35.

The main aim of this investigation was to determine the impact of a total dietary fish oil (FO) replacement by vegetable oils (soybean [SO] and canola [CO] oil) on the growth and fatty acid (FA) composition of juvenile Beluga sturgeon, Huso huso. Three practical‐type diets with equal protein and lipid content were formulated using FO, SO, and CO. Each of the diets was fed to apparent satiation five times daily to H. huso (initial weight 206 ± 7.3 g) for 120 d. All groups grew equally well. Fish weight gain, condition factor, daily growth, feed intake, feed conversion, feed efficiency, protein efficiency, and survival were not affected by diet treatment. Fish lipid composition reflected the inclusion of vegetable oils and their respective FA compositions. Monounsaturated FA and polyunsaturated FA significantly increased in fish fed the CO and SO diets, respectively, but the ratio n− 3/n− 6 were significantly reduced by the inclusion of dietary vegetable oils (P < 0.05). This study suggests that FO can be replaced by SO and CO in H. huso diets under our test conditions with no significant effect on growth. However, longer assessments of these substitutions are warranted to ensure that these treatments do not have an adverse effect on fish health.

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For studying the effect of LHRH-A 2 hormone on the induction of final maturation and ovulation of Persian sturgeon, 71 matured females and 20 matured males were used. Five groups of breeders were injected with sturgeon pituitary gland hormone (50 mg per fish) and LHRH-A 2 in dosages of 3.5, 7, 8 and 10 lg kg -1 for females and 3 and 5 lg kg -1 for males. Results showed that LHRH-A 2 successfully induced final maturation and ovulation in females, and there was no significant difference between five groups of breeders in ovulation proportion, fertilization rate, survival rate of incubation, survival of yolk-sac absorption period and active feeding period of larvae. It can be concluded that the LHRH-A 2 is a proper alternative for pituitary gland hormone in artificial propagation of Persian sturgeon.

The influence of short-term storage (3, 6 and 9 h) of Persian sturgeon (Acipenser presicus) ova outside the ovary (ex situ storage) in coelomic fluid and PSACF (Persian Sturgeon Artificial Coelomic Fluid) medium was studied at (4°C and 18°C). One mature female and three mature males were selected for gamete collection and fertilization, as well as 18 females were sampled for coelomic fluid collection. Fish were intramuscularly injected with acetone-dried sturgeon pituitary and their ova and milt collected according to common spawning methods. Thereafter ova were filtered and coelomic fluid was separated for further using in experiment on ova storage. For mimicking of ovarian fluid and designing the PSACF medium, chemical composition of ovarian fluid from 18 females was analyzed separately in 26 samples and osmolarity and pH for each sample were determined and the PSACF medium was formulated.This experiment was done with 12 treatments in 3 replicate using four factor combinations. For each treatment 5 cc (about 300) ova were used. After storage for 3, 6 and 9 h in the two test temperature, ova were fertilized with pooled sperm and then transferred to Yoshchenko incubators. Fertilization rate, hatching rate and percentage of malformed larvae were determined.Storag period and storage medium had significant effect, on fertilization rate, hatching success and malformation of larvae (P<0.05). Also, temperature had significant effects on fertilization rate (P<0.05) but no significant effects on rate of hatching and number of malformed larvae (P 0.05). Fertilization and hatching rates decreased with time (3, 6 and 9 hours of storage prior to fertilization). Malformation rates in hatched larvae increased compared to the controls. Interactions between time of storage and storage medium and temperature and the resulting effects on fertilization, hatching and malformation rates were significant (P<0.05).Using a prepared PSACF medium at 18ºC for 3 h resulted in 80.33% fertilization rate, 70.5% hatching rate and 2.6% malformation rate in newly hatched Persian sturgeon larvae.

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