AbstractThe present study was aimed to evaluate the effects of different levels of salinity on water quality, growth performance, survival rate and body composition of Pacific white shrimp in a heterotrophic/biofloc technology (BFT). Shrimp post-larvae with an average weight of 74.46 mg were cultured in 300 L fiberglass tanks containing 130 L water at a density of 1 post-larva/L. Three treatments including different levels of salinity of 8, 21 and 32 ppt with three replicates were considered. The highest levels of body weight, growth rate, specific growth rate, increase in body length and survival rate were observed at high salinity level (32 ppt). The highest feed conversion ratio (FCR) and the lowest level of feed efficiency were obtained in shrimps cultured at lowest salinity level (P<0.05). Biochemical analysis of shrimp body composition showed an increase in protein, lipid and ash content as the salinity elevated (P<0.05). The zero-water exchange system used in this study had no significant effects on water quality parameters. The results of the present study concluded that high salinity level (32 ppt) improves the growth and survival of the biofloc supplemented Pacific white shrimp in a BFT system.

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Steroids both in seminal fluid (SF) and blood serum (BS) as well as the milt quality (sperm motility and sperm production) were investigated during final maturation of Persian sturgeon. The BS levels of testosterone (T), 11-Ketotestosterone (11-KT), progesterone (P), 17α,20β,21-trihydroxy-4-pregnen-3-one (20βS), cortisol (C) and 17α,hydroxyprogesterone (OHP) elevated after pituitary preparation (PP) treatment and then decreased during stripping period for spermiating males. Such elevations did not occur for non-spermiating individuals and steroids remained in basal levels after PP treatment until the end of stripping period. For both groups (spermiating and non-spermiating fish), the BS levels of 17α,20β-dihydroxy-4-pregnen-3-one (DHP) did not show significant changes during experiment. During stripping period, the values of all tested steroids were significantly lower in SF than in BS of spermiating males. SF levels of 20βS and 11-KT showed a decreasing trend and the other steroids were unchanged during this period. Significant positive correlations were found between the values of 20βs and 11-KT in BS with their levels in SF. Also, BS and SF levels of 20βs and 11-KT were positively correlated with sperm motility characteristics (percentage and duration of motility) and sperm production (sperm density and milt volume), respectively. The results showed the probable involvement of 20βs, P, OHP, T, 11-KT and C in final maturation of Persian sturgeon, especially 20βs and 11-KT had good correlations with qualitative parameters of milt. The lower levels of steroids in SF than those in BS might also be essential for viability of Persian sturgeon spermatozoa. Probably, there are mechanisms that stabilize the concentrations of a number of hormones in the SF.

Sperm motility and sperm production as well as organic and inorganic components present in the seminal plasma were measured at different time periods of spermiation during the spawning season in order to evaluate the semen quality in Caspian brown trout, Salmo trutta caspius. For such evaluation, males were divided into four groups based on the date of spermiation: group A (pre-mature broodstocks), group B and C (mid-mature broodstocks), group D (late-mature broodstocks). Our results showed that the Caspian brown trout produces semen of variable quality depending on the date in the period of spermiation. In this regard, the percentage of motile spermatozoa, duration of motility, sperm density, osmolality and also the concentrations of Na + , Cl -, K + , Ca 2+ , Mg 2+ and total protein content were significantly higher in mid-mature broodstocks (which matured in the middle of spawning season, i.e. groups B and C) compared to pre-mature (group A) and late-mature (group D) samples. Statistically significant positive correlations were also found between these semen parameters: sperm production vs Na