The objective of this study was to test existing ultrasound technology for use in early sex identification in beluga sturgeon (3-years-old fish) while including some methodological adjustments. Eighty cultured Beluga sturgeons aged 3 years underwent ultrasonographic examination using a high frequency transducer for sex determination. Sexing of the sturgeons was based on the shape and echogenicity (brightness) of the gonad and surrounding fat tissue in sonographic scans. Accuracy of ultrasound sex determinations were confirmed through directly inspecting the gonads by a small incision in the right or left ventral body wall. Females were identified with 96.7% accuracy (n = 31) and males with 97.9% accuracy (n = 49). Overall accuracy of sex determination using ultrasonography was 97.5%. Using high frequency transducer and transverse scanning just over the swim bladder in 3-year-old beluga may have been contributed in high accuracy sex detection. These technically improvements may be considered an advantage for beluga culture because this fish matures extremely late compared to other sturgeon species.
This study examined the correlation between egg size and a number of variables in the subsequent larval stages of the Persian sturgeon Acipenser persicus. Nineteen female sturgeons were fertilized and the eggs were harvested. The results showed that there were positive, significant correlations ( p 5 0.05) between egg size and several dependent variables including larval weight and duration of hatching time as well as the volume of the yolk sac and the hatching time. The weight of larvae at 2, 4, 6 and 8 days post hatching showed positive and significant correlation ( p 5 0.05) with egg size. Total length of larvae at 2, 4, 6, 8 and 10 days post hatching had significant correlation ( p 5 0.05) with egg size in all cases. During yolk sac absorption at 2, 4, 6, 8 and 10 days after hatching correlations gradually decreased. There was no significant correlation between egg size and mortality during the yolk sac absorption period (r ¼ À0.24, p ¼ 0.314) or the first feeding stage (r ¼ À0.05, p ¼ 0.840).
The objective of this work was to study the relationship between female size (weight) and variables of egg and larval stage of Persian sturgeon Acipenser persicus. In this study, 19 female breeders were captured in Caspian Sea and fertilized by routine methods. Positive significant correlations (P<0.05) were established between female weight and ovulated eggs per female, time of second mitosis division and volume of yolk‐sac at hatching. There was not significant correlation (r=0.33, P=0.161) between female weight and egg diameter. Female weight was not affected weight of larvae at hatching time (r=0.37, P=0.119), as well as larval length (r=−0.14, P=0.558) and larval weight at the end of the experiment (48 hours after first feeding) (r=0.16, P=0.491). Mortality rate during yolk‐sac absorption was higher with increased female weight but their correlation was not significant (r=0.40, P=0.076). During the first feeding stage, mortality rate was 13.39% and there was no significant correlation between mortality rate in this period and female weight (r=−0.12, P=0.613). Conclusively, as a result female size influenced fecundity, time of second mitosis division and yolk‐sac volume at hatching time without affecting mortality rate during yolk‐sac absorption and first feeding stage in Persian sturgeon. Thus, smaller female broods do not cause more mortality than larger ones in larval production and they can be used in reproduction procedure.
Abstract. The correlation of proximate composition and fatty acid content of the meat of brackish-water kutum, Rutilus frisii kutum (Kamensky), warm-water silver carp, Hypophthalmichthys molitrix (Val.), and cold-water rainbow trout, Oncorhynchus mykiss (Walbaum) were determined in relation to body weight. In silver carp, body protein increased (r = 0.574, P = 0.032) with increased body weight while moisture decreased (r = -0.789, P = 0.000). In kutum and rainbow trout the contents of protein and lipid were independent of fish size (P > 0.05). The n-3 polyunsaturated fatty acids of silver carp meat increased with body weight (r = 0.592, P = 0.033), while n-6 fatty acids decreased (r =-0.667, P = 0.013). The results indicated the important advantages of the nutritional quality of fish of different sizes in the human diet.
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