Aquaculture performance of phase II and phase III sunshine bass (a female white bass Morone chrysops ϫ male striped bass M. saxatilis), palmetto bass (a female striped bass ϫ male white bass), and white bass were evaluated in separate 12-week yield trials conducted in indoor recirculating-water systems. Phase II sunshine bass, palmetto bass, and white bass had mean initial weights of 40.0 g, 39.7 g, and 41.0 g, respectively. A diet containing 40.2% crude protein (CP) was fed to fish twice daily at a rate of 3% body weight/d. At the end of the trial, sunshine bass and white bass had mean weights of 124.2 g and 126.0 g, respectively and were significantly larger than palmetto bass (93.5 g mean weight). Phase II sunshine bass and white bass outperformed palmetto bass by having higher relative growth (h), mean daily growth, and relative weight, as well as better feed conversion ratios (weight of food fed/weight gained). Survival was 100% for all three taxonomic groups. In the phase III study, mean initial weights for sunshine bass (177.5 g) and palmetto bass (185.9 g) were similar but significantly greater than the mean initial weight of white bass (153.8 g). In this trial, fish were fed a floating trout chow (44.1% CP) to satiation twice per day. At the termination of the study, sunshine bass (611.1 g) and palmetto bass (517.8 g) had significantly greater mean weights than white bass (254.4 g). Significant differences among all three taxonomic groups were found for h and for mean daily growth rate. Both crosses of hybrid striped bass had lower feed conversion ratios when compared with white bass. Relative weight values (ratio of a fish's weight to the weight of a standard fish of the same length) for sunshine bass were significantly greater than values for palmetto bass and white bass. Survival rates ranged from 98% to 100% for the three taxonomic groups. Differences were not detected between sunshine bass and palmetto bass for eviscerated percentage, headed and eviscerated percentage, or dressout percentage. Sunshine bass outperformed palmetto bass at phase II and phase III sizes under the conditions of this study.

No abstract

The efficacy of oxytetracycline hydrochloride (OTC-HCl) in controlling external columnaris disease caused by Flavobacterium columnare on fingerling walleyes Sander vitreus and channel catfish Ictalurus punctatus was evaluated in two on-site hatchery trials. Microscopic examination of skin scrapings before treatment confirmed the presence of bacteria with characteristics indicative of F. columnare. In separate trials, walleyes (4.4 g) and channel catfish (1.5 g) were exposed to 60-min static bath treatments of OTC-HCl at 0, 10, and 20 mg/L (walleyes) or 0, 10, 20, and 40 mg/L (channel catfish) on three consecutive days. Each treatment regimen was tested in triplicate, and each replicate contained either 30 walleyes or 55 channel catfish. Posttreatment presumptive disease diagnosis indicated that F. columnare was the disease agent causing the mortality in both species of fish. Walleye survival at 10 d posttreatment was greater in the 10-and 20-mg/L treatment groups than in the control group; however, only the 10-mg/L treatment significantly (P , 0.05) increased walleye survival in comparison with controls. In the channel catfish trial, survival at 10 d posttreatment was significantly (P , 0.05) greater for all OTC-HCl treatment groups relative to controls. Results from these trials indicated that OTC-HCl treatments effectively reduced mortality in walleyes (10 mg/L only) and channel catfish infected

Spawning trials were conducted to determine an efficacious dosage of human chorionic gonadotropin (hCG) and to investigate the potential of mammalian gonadotropin releasing hormone analog (mGnRHa) to induce ovulation in white bass Morone chrysops. White bass broodstock were habituated to indoor tanks and subjected over several months to photoperiod-temperature regimes simulating the seasons to induce gonadal maturation. Various hCG dosages (0, 10, 25, 50, 150, 170, 250, 280, and 830 IU/kg body weight) were tested in single injections. We demonstrated that white bass can be successfully spawned with an hCG dosage as low as 50 IU/kg. However, this dosage did not result in all fish ovulating in a subsequent trial. We found no significant differences between 150 IU hCG/kg and higher dosages in ovulation response (ovulation success and time to ovulation), egg production (number of eggs/kg), or egg quality (fertility and hatch rates). Single injection of mGnRHa at 50 g/kg did not consistently cause ovulation in white bass. Use of pimozide, a dopamine antagonist, along with mGnRHa, did not significantly improve ovulation response, egg production, or egg quality in white bass. No significant differences existed in spawning response, egg production, or egg quality when 24-h and 48-h intervals between mGnRHa and hCG injections were used or between these protocols and hCG treatment alone. We recommend an hCG dosage at 150 IU/kg if ovulation is to be induced via a single hormone injection.

This study used six 0.04 ha plastic-lined ponds to compare the e¡ects of a fertilization regime using a one-time initial application of an organic fertilizer (alfalfa pellets) with the current regime of weekly applications of organic fertilizers on the abundance and distribution of aquatic invertebrates and walleye, Sander vitreus, ¢ngerling production. Walleye, 3^4 days post hatch, were stocked on 1 May 2002 and harvested on 6^7 June 2002. Throughout the growing season, a ratio of 7:1total nitrate-nitrogen to total phosphorus was maintained in all ponds regardless of the treatment. Once fry were stocked, ponds in Treatment #1 were fertilized weekly with organic fertilizer (alfalfa pellets; 112 kg ha À 1 week À 1 ) for a total of 795 kg ha À 1 pond À 1 . Ponds in Treatment #2 only received an initial application of alfalfa pellets (112 kg ha À 1 ). Ponds inTreatment #1had sig-ni¢cantly higher ammonia and nitrate levels as well as higher chironomid larvae but not zooplankton compared with the other treatment. At harvest, walleye in the Treatment #1 ponds were signi¢cantly longer and heavier; however, the survival and relative weight were not signi¢cantly di¡erent. These results suggest that weekly applications of organics are important for the benthic food base and growth of ¢ngerling walleye reared in plastic-lined ponds.