Growth performance of juvenile white sturgeon as affected by feeding regimen

Juvenile (mean +/- SE, 8.6 +/- 0.1 g) white sturgeon Acipenser transmontanus were fed for 8 weeks under one of six feeding regimens: continuously 24 h/d (C24); continuously 12.8 h/d during the day (C12/D), continuously 12.8 h/d at night (C12/N), 6 meals/d (M6), 4 meals/d (M4), and 2 meals/d (M2). Specific growth rate, feed efficiency, and body lipid content were significantly (P < 0.05) affected by the feeding regimen. These variables were highest in the C24 group and lowest in the M2 group; fish in the M6 group showed the second best performance. Specific growth rate and feed efficiency in terms of wet weight in the M6 groups were not significantly different from those in the C24 groups, but specific growth rate in terms of energy and energy retention efficiency were significantly lower. Feeding regimen had no effect on condition factor, hepatosomatic index, coefficient of variation in final body weight, and protein and ash contents. There was no significant difference in these indexes between 12.8-h/d continuous feeding by day or by night. It was concluded that continuous feeding for 24 h/d was the optimum feeding regimen for juvenile white sturgeon.

An efficient methodology for cryopreservation of spermatozoa of red seabream, Pagrus major, with 2-mL cryovials

The aim of this study was to optimize the cryopreservation protocols for the sperm of red seabream, Pagrus major. The 2-mL cryovials and programmable freezer were employed for cryopreservation. Six extenders, six cryoprotectants in various concentrations ranging from 6 to 20% (v/v), four cooling rates, and three thawing temperatures were evaluated by postthaw sperm motility and fertility. The ratio of sperm to egg for postthaw sperm fertilization trials was experimentally standardized and was optimal at 500:1. The best motility of postthaw sperm (79.4 +/- 4.7% to 88.6 +/- 8.0%), fertilization rates (89.6 +/- 2.9 to 95.6 +/- 1.9%), and hatching rates (85.3 +/- 5.1% to 91.4 +/- 4.3%) were achieved when Cortland extender, dimethyl sulfoxide (15, 18, and 20%) or ethylene glycol (9, 12%) as cryoprotectants, 20 C/min as the cooling rate, and 40 C as the thawing temperature were employed. Moreover, the results on embryonic development were not significantly different between cryopreserved sperm and fresh sperm during incubation process. In conclusion, these methods of cryopreservation of red seabream sperm are suitable for routine aquaculture application and preservation of genetic resources.