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The milt of individual males of Siberian sturgeon (Acipenser baerii) and sterlet (Acipenser ruthenus) was frozen without cryoprotector (at -79°C) or cryopreserved with methanol as the cryoprotector. The activity of arylsulfatase (AS), acid phosphatase (AcP), β-N-acetylglucosaminidase (NAGase), and protein concentration was determined. The protein concentration and enzymatic activities in supernatant obtained after cryopreservation were higher than in milt plasma, but they were lower than that in the material obtained after freezing at -79°C. The protein and enzymatic leakage of sterlet spermatozoa was statistically higher in supernatants that had been frozen at-79°C than in those that had undergone cryopreservation. Differences in the protein and AS leakage the Siberian sturgeon supernatants were also observed.
Within 17 September – 31 October 1997, fry of the Russian × Siberian sturgeon hybrid of 31.1 g mean individual weight and sterlet fry of 25.4 g mean individual weight were fed two trout feeds: the Dana–ex 4.85 and the Safir differing, i.a., in their gross energy content (5470 and 5173 Kcalˇg–1, respectively), each feed being offered in triplicate. The fish were kept in cages, stocked at 80 ind./cage, placed in power station cooling water of temperature changing within 12.2–23°C. Water temperature–dependent differences in fish growth were revealed: the hybrid grew better at 19–23°C, while the sterlet growth was better at 12–18°C. In both fish groups, the Dana–ex 4.85 produced better food conversion rate (FCR) and apparent net protein utilisation (aNPU).
Experimental rearing of sterlet using forms with normal and albino coloring was conducted. The spawn was fertilized as follows: spawn from females with normal coloring were fertilized with milt obtained from males with normal coloring (group CC) and with that from albino males (group CB); spawn from albino females were fertilized with milt obtained from males with normal coloring (group BC) and with milt obtained from albino males (group BB). It was confirmed that the hatch inherited parental coloring; there were only individuals with dark coloring in group CC, while in group BB, there were only albino individuals. However, in groups BC and CB, in addition to the majority of individuals that inherited color, there were individuals of median coloring. The highest hatch survival rate was noted in group CC at 97.3%, and the lowest was noted in group CB at 94.8%. The hatch with albino coloring had the slowest growth rate.
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