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Browsing by Author "Nunley, Chad E."

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    Growth and Production Characteristics of Palmetto Bass (Morone saxatilis female x Morone chrysops male) Reared at Three Densities in a Pilot-scale Recirculating Aquaculture System
    Brazil, B. L.; Nunley, Chad E.; Libey, George S. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2001-06-01)
    Production characteristics of palmetto bass (Morone saxatilis female x Morone chrysops male) reared at three stocking densities (36 fish/m3, 72 fish/m3, and 144 fish/m3) in a pilot-scale RAS were evaluated. A final mean ±SE fish weight of 412.1 ± 7.8 g at the high density was significantly lower than that of fish at the medium density weighing 542.1 ± 11 .8 g (P < 0.05). Fish weight (676.1 ± 17 .0 g) at_ the lowest density was significantly higher than at the high and medium densities (P < 0.05). The average daily weight gain at the low density (2.8 g/d) was 22% and 47% higher than fish reared at the medium and high densities, respectively. Total biomass gains of 733.8, 483.3, and 297.9 kg were obtafued at the high, medium, and low densities. Feed conversion and survival rates were similar among densities averaging 1.4 and 97 .1 %, respectively. Higher mean daily and cumulative feed totals at the highest density contributed to significantly higher ammonia and nitrite concentrations and lower pH levels at haryest. All other measured water quality parameters were similar among densities and remained within known acceptable limits for fish growth. The results indicated that palmetto bass reared in closed systems reached market size in 224 days at the low and medium densities. However, the relative biomass production may not justify such strategies when compared to the yield obtained at the highest rearing density.
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    Production of hybrid striped bass (Morone chrysops x Morone saxatilis) in a recirculating aquaculture system
    Nunley, Chad E. (Virginia Tech, 1992)
    TRIAL 1 A preliminary study was conducted to evaluate growth, survival and feed conversion of reciprocal cross hybrid striped bass (Morone chrysops female x Morone saxatilis male) cultured in pilot-scale recirculating aquaculture systems. Hybrid striped bass were stocked in nine 12,500 liter recirculating systems at a mean density of 149 fish/m³. Mean weight at stocking was 40.6 g. Overall survival averaged 72.5%. One system experienced 100% mortality due to the loss of the recirculating pump. Three systems experienced significant mortalities in the middle of the study due to unknown causes. Survival was high, averaging 93.5%, in the remaining systems. Mean daily growth rate of 1 g per day and mean feed conversion of 1.67 compared favorably with that reported in the literature for hybrid striped bass. Slow start-up of new biofilters led to a restricted feeding regime and limited growth. Mean fish weight at harvest averaged 262.1 g with total biomass in the tank averaging 452.57 kg. The recirculating system maintained water quality within ranges adequate for good growth, but the stocking density may have surpassed the systems maximum capacity. TRIAL 2 Results from Trial 1 indicated a need to reduce stocking densities. In Trial 2, three densities of reciprocal cross hybrid striped bass, high (144 fish/m³), medium (72 fish /m³) and low (36 fish/m³) were stocked in eight pilot-scale recirculating systems (12,500 L) and evaluated over 224 days. At stocking, mean weights averaged 34.9, 50.8, and 43.4 g for the high, medium and low treatments, respectively. Fish were hand fed a high protein (44%) floating pellet twice daily. Final weights averaged 412.2 g, 541.1 g, and 676.1 g in the high, medium and low density treatments, respectively. No difference in mean weights were detected between the high and medium densities, but those in the low density were significantly greater (p < 0.05) than the medium and high densities. Total biomass was significantly different (p < 0.05) between treatments at the end of the study and inversely related to mean weight gain, averaging 733.8 kg in the high, 483.3 kg in the medium, and 297.9 kg in the low density treatments. The water quality parameters measured were similar among treatments and adequate for good growth. Feed conversions averaged 1.43 and were not significantly different between treatments. Survival averaged greater than 95% in all treatments. The results of this study demonstrated that hybrid striped bass can grow from fingerling to market size in 224 days in recirculating systems at densities of 36 and 72 fish/m³. If environmental conditions are adequately maintained, it is anticipated that higher densities could reach market size in the same time period. Overall results indicate that hybrid striped bass have good potential for culture in recirculating aquaculture systems.