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Submitted to: Book of Abstracts World Aquaculture Society
Publication Type: Abstract Only Publication Acceptance Date: 12/1/2009 Publication Date: 3/1/2010 Citation: Green, B.W. 2010. Rearing channel catfish in a bioflac production system [abstract]. Book of Abstracts World Aquaculture Society. p.400. Interpretive Summary: Technical Abstract: Production of channel catfish in an intensively managed mixed suspended-growth, or biofloc, production system was investigated in two studies. Management of unassimilated feed nitrogen is important as feeding rate is increased in intensified production systems. In a mixed suspended-growth production system, phytoplankton uptake and microbial processes that occur in the water column control water quality. Although tilapia and marine shrimp, which can derive nutrition from the biofloc, typically are grown in a biofloc production system, fish like the channel catfish also can be reared using this production system. The effect of stocking rate and initial biomass of channel catfish on yield and water quality was investigated. In the first trial, channel catfish were stocked into HDPE-lined tanks (18.6 m2, 15.5 m3) at 7.5, 12.5, or 17.5 fish/m2 and grown for 138 d. In the second trial, channel catfish were stocked in April with 12.5 fish/m2 at an initial biomass of 0.43, 0.97, or 1.91 kg/m3. One 1.865-kW blower/3 raceways provided air continuously through a diffuser grid on the bottom of each raceway. Fish in each trial were fed daily to apparent satiation with a 32% protein floating extruded feed. Dissolved oxygen and temperature were measured on a daily basis, and water quality variables (pH, TAN, NO2, NO3, SRP, settleable solids, total suspended solids, and chlorophyll a) were measured on a weekly basis. The net yield increased linearly (R2 = 0.60) from 3.1 to 4.8 kg/m3 as stocking rate increased from 7.5 to 17.5 fish/m2 in the first trial. Mean net daily yield was high and ranged from 22.2-35.0 g/m3/d. Mean daily feed consumption by fish at the 12.5 and 17.5 fish/m2 stocking rates was 52.8 and 58.5 g/m3/d, respectively, significantly greater than the 36.1 g/m3/d of feed consumed by fish at the 7.5 fish/m2. High feeding rates were sustained from late August through mid-October and averaged 51.4, 79.9, and 79.1 g/m3/d, for the 7.5, 12.5, and 17.5 fish/m2 treatments, respectively. Tank water quality variables were impacted differentially by cumulative feed addition. Mean total suspended solids, nitrate-nitrogen, and soluble reactive phosphorus concentrations increased linearly with increased cumulative feed addition. Mean chlorophyll a concentration decreased linearly with increased cumulative feed addition. Nitrate-nitrogen concentration began to increase in early July, indicating the onset of nitrification, and continued to increase throughout the remainder of the experiment. Results from the second trail will be presented. |
