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Title:   Author  item
                                            Green, Bartholomew

                                                         - *Bart*item
                                            Schrader, Kevin
  Submitted to: Book of Abstracts Aquaculture America
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 9/25/2012
                                    Publication  Date: 2/21/2013
                                    Citation: Green, B.W., Schrader, K. 2013. Effect of initial biomass on channel catfish yield and water quality in a biofloc technology production system [abstract]. Book of Abstracts Aquaculture America 2013: Strike a Chord for Sustainable Aquaculture, February 21-25, 2013, Nashville, Tennessee. p.427.Interpretive Summary:
                                Technical Abstract: Biofloc technology (BFT) production systems are being used more commonly to produce high yields of fish or shrimp because very high feed rates are possible.  In an outdoor BFT production system, a complex of living organisms is closely associated with particulate organic matter and is maintained in suspension by continuous aeration.  Ammonia excreted by the culture animal is utilized by the phytoplankton and bacteria that are part of this complex of living organisms.  Results of previous research with channel catfish (Ictalurus punctatus) in a BFT production system showed that net yield increased linearly as initial biomass increased from 0.4-1.4 kg/m**3.  The objective of this study was to evaluate the effect on net yield and water quality of higher initial channel catfish biomasses using a completely randomized experimental design. Stocker catfish (217.0 g/fish, 30.5 cm/fish) were stocked into nine continuously aerated HDPE-lined tanks (18.6 m**2, 15.5 m**3) at 1.4, 2.1, or 2.8 kg/m**3.  Fish were fed daily to apparent satiation with a 32% protein floating extruded feed.  Dissolved oxygen and temperature were measured continuously using sensors connected to a data logger.  Water quality variables (pH, TAN, NO2N, NO3N, SRP, total alkalinity, settleable solids, total suspended solids, total volatile solids, and chlorophyll a) were measured on a weekly basis. Water samples also were analyzed periodically for the off-flavor compounds, 2-methylisoborneol (MIB) and geosmin.  Survival was high, did not differ among treatments, and averaged 97.2%.  The increase in mean net yield of channel catfish in relation to initial biomass was curvilinear.  Mean net yield ranged from 3.8 – 5.5 kg/m**3.  Mean individual weight of catfish at harvest decreased linearly as stocking biomass increased.  Low, variable concentrations of MIB and geosmin were present in biofloc tank water during most of the study No significant difference among treatments was detected for MIB or geosmin concentrations in BFT tank water.  Concentrations averaged 3 ng/L MIB and 2 ng/L geosmin.  This study further supports our previous observations that episodes and intensity of MIB- and geosmin-induced off-flavor in channel catfish are substantially lower than for pond-reared catfish.


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