World Aquaculture Magazine - September 2021

52 SEP TEMBER 2021 • WORLD AQUACULTURE • WWW.WA S .ORG Split Ponds Commercial catfish farmers are intensifying production by retrofitting ponds with variations of the partitioned aquaculture system originally developed by Dr. Les Torrans at University of Arkansas Pine Bluff and Dr. David Brune at Clemson University (Tucker et al. 2014). The split- pond system developed by Mississippi State University and USDA-ARS Scientist, Dr. Craig Tucker, is the most common variation used commercially. The split pond consists of a small fish-holding basin (15-20 percent of total area) connected to a much larger basin (80-85 percent of total area) that functions as a waste-treatment lagoon and a source of photosynthetically produced oxygen during daylight. The basins are connected by two conduits and fish escape is prevented by using screens or barriers. Water is circulated between the two basins to remove nitrogenous waste and provide oxygenated water to the fish- holding basin. IntensivelyAerated Small Ponds Studies consistently show that feed intake, growth and feed conversion efficiency of catfish are not affected when the minimum dissolved oxygen concentrations remain at or above 3 mg/L (Torrans 2008, Torrans et al. 2015) if afternoon concentrations rise to near saturation or above. If the minimum dissolved oxygen concentration is allowed to fall below 3 mg/L, feed intake, growth and production of channel, blue and channel × blue hybrid catfish all decrease. Intensive aeration (aeration rates above 9.3 kW/ha) works best in moderate-size ponds (1-2 ha) rather than the larger traditional C atfish farming continues to be the largest segment of US aquaculture (USDA-NASS 2019) contributing 74 percent of US finfish production. The industry reached its peak to date with 79,559 ha in 2002 and 300,323 t produced in 2003. Production is centered in the states of Mississippi, Alabama, Arkansas and Texas (USDA-NASS 2021). The US catfish industry went through a contraction phase from 2003- 2013 due to the combined effects of competition from pangasius catfish imports from Vietnam, the 2001 recession, the September 11, 2001 terrorist attacks and a period of historically low fish prices (Engle et al. 2021). Despite such a decline in area, total production has increased over the last six years (Fig. 1). (It should be noted that total production in 2020 dropped due to the impact of the COVID-19 pandemic.) US catfish producers have been able to increase fish productivity by adopting new intensive production systems and complementary technologies. Production Systems A recent survey of catfish producers in Mississippi, Arkansas and Alabama (tristate area) quantified trends in the adoption of productivity-enhancing technologies and found a trend of increasing intensification (Hedge et al . 2021). Alternative catfish production systems such as split ponds and intensively aerated small ponds (Fig. 2) have been increasingly adopted by the catfish industry. About 31 percent of the catfish production area had adopted these intensive systems at the time of the survey (Fig. 3). These systems produce greater yields than traditional systems on a per hectare basis (Fig. 4). US Catfish Production Is Becoming More Efficient Jimmy Avery, Shraddha Hedge and Ganesh Kumar FIGURE 2. Intensively aerated ponds (foreground) and split ponds (immediately behind the intensively aerated pond). Photo: Daniel Oberle, USDA-Agricultural Research Service, Stoneville, Mississippi, USA. FIGURE 1. Gross yield (kg/ha) of commercial catfish production in the United States. A recent survey of catfish producers inMississippi, Arkansas and Alabama (tristate area) quantified trends in the adoption of productivity-enhancing technologies and found a trend of increasing intensification. Alternative catfish production systems such as split ponds and intensively aerated small ponds have been increasingly adopted by the catfish industry.