Fish from two genetically identified populations of largemouth bass Micropterus salmoides, representing the northern subspecies M. s. salmoides (N x N) and the Florida subspecies M. s. floridanus (F x F), and their reciprocal F\ hybrids (F x N and N x F; female represented first) were stocked in 0.04-0.48-hectare ponds and evaluated for growth, condition, and percent survival during the second year of life. Angling and seine-capture vulnerability were also examined.The F x N cross was significantly heavier and had a significantly higher relative weight (100 [individual weight/standard weight at length]) than the other crosses at the end of the study. The F x F cross was significantly shorter, weighed less, and was in poorer condition than all other crosses. The N x N cross was generally more susceptible to angling than the F x F cross. The F x F cross was significantly less vulnerable to seine capture than the other three crosses.
The endangered razorback sucker Xyrauchen texanus is endemic to the Colorado River system in western North America and is threatened with extinction because of limited recruitment. To assist in management and recovery efforts, we developed methods for the cryopreservation of sperm, evaluated the influence of various factors on motility of thawed sperm, and examined the effect on fertilization of cooling rate and the addition of caffeine. Sperm samples cryopreserved with 10% methanol (MeOH) had significantly higher postthaw motility than did samples preserved with 5% or 20% MeOH or with 5% or 10% dimethyl sulfoxide, N, N‐dimethylacetamide, glycerol, propylene glycol, or ethylene glycol. Sperm samples cryopreserved in 0.5‐mL and 2.5‐mL straws had significantly higher postthaw motility than did samples cryopreserved in 0.25‐mL straws. Exposure to 10% MeOH for up to 30 min did not significantly influence sperm motility before freezing or after thawing. Cooling rate (−21°C/min or −91°C/min) did not significantly influence sperm motility. Samples thawed in a water bath at 20°C, 30°C, or 40°C had significantly higher motility than did samples thawed on the laboratory bench (19°C). Refrigerated sperm had significantly higher motility after the addition of 0.005 M caffeine; however, caffeine did not increase the motility of thawed sperm. Fertilization percentage was 41 ± 31% for the egg quality control treatments (fresh sperm) in the freezing rate study. The freezing rate of −91°C/min yielded 66% fertilization relative to the control (actual value, 27 ± 26%), which was significantly higher than the 12% fertilization (actual, 5 ± 3%) yielded by the freezing rate of −21°C/min. Fertilization percentage was 25 ± 24% for the egg quality control treatments in the caffeine study. Caffeine‐treated sperm yielded 60% fertilization relative to the control (actual, 15 ± 13%), which was significantly higher than the 16% fertilization (actual, 4 ± 4%) yielded by sperm without caffeine treatment.
A study was conducted to determine if fingerlings of two strains of largemouth bass, Micropterus salmoides, differed significantly in acceptance of formulated feed. The San Marcos (Marion) and Inks Dam (northern) strains of largemouth bass were trained at the San Marcos National Fish Hatchery and Development Center to accept formulated feed, Biodiet, under similar conditions in a simulated production environment. Fingerlings (average total length, 30 mm) that had been reared under similar conditions were stocked at equal densities, in triplicate, in indoor rectangular tanks. They received semimoist pellets, 1.6 mm in diameter, at a rate equal to 15% of the stocked biomass per day throughout the training period. Training success was 23% for the Inks Dam and 43% for the San Marcos strain. The San Marcos strain performed 84% better than the Inks Dam strain under similar conditions. These results appear to support the contention that genetic difference explains to a considerable extent the difference in training success between strains. These data, plus previous experience with both strains, suggest that significant gains in production and management may be possible if the genetic potential of different strains of largemouth bass is exploited.
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