Comparing Economic Returns of Dissolved Oxygen Management in Commercial Catfish Production
Holland, Leigh Wilson
Type of DegreeMaster's Thesis
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Catfish culture is one of the largest forms of aquaculture in the US. Catfish production systems have been able to achieve production up to almost 12,000 kg ha-1 year-1 (Bott, 2015) since the increase in availability of hybrid catfish fingerlings in 2008. The goal of this research is to evaluate the production and economic returns of two commercial catfish operations under traditional and experimental systems of oxygen management. A west Alabama farm agreed to install two floating in-pond raceways cells in each of two commercial ponds (0.8 cells/ha), called raceway ponds. One cell was stocked with channel catfish the other with hybrid catfish. A Mississippi Delta farm agreed to an increased range of paddlewheel aeration rates from 6.8 to 18 kW/ha and grew hybrid catfish in open ponds. Diffused air hoods (2.3 kW/ha) were added to 13.7 kW/ha of paddlewheel aeration as an alternative treatment. Mechanical mixing equipment (2.3 kW/ha) was added to 13.7 kW/ha of paddlewheel aeration as a second alternative treatment. The open ponds were equipped with commercially available remote dissolved oxygen (DO) probe and aeration controls. Aerator run time and amperage readings were used to estimate power usage. Change in nightly DO readings near saturation was used to estimate whole pond respiration. Whole pond respiration was used in an attempt to compare waste loads between ponds. All cells exhibited mean daily minimum dissolved oxygen levels at or above 3.5 mg/L. Raceway cells were harvested (before market size) after four months of growth (July 2014-October 2014). Production was 1,236 and 2,734 kg/ha when channel and hybrid catfish were raised, respectively. Feed conversion ratio (FCR) was 1.75 and 1.46 for channel and hybrid catfish, respectively. The raceways exhibited higher feed efficiency than the industry average like previous versions of in-pond raceways Since fish in raceway cells did not reach market size a sale price of $2.75 /kg was projected. The resulting cost of production in the raceways was $3.61/kg and $2.83/kg when channels and hybrid catfish were raised, respectively. The number of cells was projected to 2.43 cells/ha and recalculated costs of production were $2.98/kg and $2.52/kg for channels and hybrid catfish, respectively. So the experimental (0.8 cells/ha) raceways were not profitable when channel catfish or hybrid catfish were grown. However, in a sensitivity analysis, the projected commercial analysis was profitable when hybrid catfish were grown. Open ponds were harvested after approximately one year. The average mean daily minimum DO was 3 mg/L for the open ponds. A feed problem caused five of the ten open ponds to experience fish losses due to anemia. The average cost of production ($/kg) ranged from 1.94 to 2.31 for open pond treatments. Open pond production (kg/ha) increased with oxygen management (kW/ha) up to 18.75 kW/ha. Although increased production (kg/ha) usually relates to increased profits ($/ha), lower survival in open ponds affected feed efficiency which decreased profitability. Average production ranged from 9,539 to 24,509 kg ha-1 year-1 across the range of open pond treatments with FCR from 2.4 to 2.9. Ponds with paddlewheel aeration and a mechanical mixer exhibited similar production in ponds that used paddlewheel aeration alone. Ponds that used diffused air hoods and paddlewheel aeration achieved (15%) higher production than paddlewheel aeration alone. Six open ponds contained oxygen management equipment over 13.7 kW/ha. Five of these six ponds produced over 20,000 kg/ha versus the average production in the Alabama catfish industry of less than 7,000 kg/ha (Courtwright, 2013). Whole pond respiration was moderately correlated to feed input (R> 0.5) in open ponds. Ponds with mixing equipment (diffused air or mechanical) indicated that the equipment may manage waste loads better than paddlewheel aeration alone. In conclusion, open pond results confirm that production increases with oxygen management up to at least 18 kW/ha of aeration.