Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract Only
Publication Acceptance Date: December 13, 2006
Publication Date: February 26, 2007
Citation: Green, B.W. 2007. Production of Catfish in a Microbial-Based System [abstract]. Book of Abstracts Aquaculture America. p. 359.
Most channel catfish (Ictalurus punctatus) produced in the U.S. is reared in intensively managed earthen ponds. Catfish yield (kg/ha) has increased as the industry has developed during the past 30 years, but further increases in yield appear difficult using current pond configurations and management practices. Catfish yield only can be increased through increased loading limits that result from increased waste assimilation capacity of the pond. Intensively managed, microbial-based production systems have been used to increase production of marine shrimp (Litopenaeus vannamei), tilapia (Oreochromis sp.) and hybrid striped bass (Morone saxatilis X M. chrysops), and appear to offer potential for increasing catfish production beyond current pond limits.
Two trials to evaluate the stocking rate-growth/yield relationship were conducted in 9 38-m3, HDPE-lined raceways with a center divider and each equipped with a continuously operating 0.37 kW electric paddlewheel aerator. In Trial 1, channel X blue hybrid catfish (Ictalurus punctatus X I. furcatus) were stocked at 25, 50, 75, 100, 125, 150, 175, 200, or 225 fish/raceway. In Trial 2, channel X blue hybrid catfish were stocked at 100, 300, or 500 fish/raceway. Mean initial individual weights were 0.085 and 0.069 kg/fish in Trials 1 and 2, respectively. Salt was added to maintain chloride concentration about 100 mg/L. Fish were fed a 32% protein floating feed to satiation daily. Flour was added to tanks as a source of carbon. Water pH was monitored on a daily basis, and samples analyzed weekly for chlorophyll a, and dissolved inorganic nitrogen and phosphorus. Trail 1 was harvested 187 d after stocking. Trial 2 is on going.
Fish survival in Trial 1 ranged from 60-80%, and averaged 70%. Final catfish biomass increased linearly from 0.22-1.34 kg/m3 as the stocking rate increased from 25-225 fish/raceway (0.7-5.9 fish/m3). Mean individual weight at harvest was independent of number of fish at harvest up to approximately 80 fish/raceway (2.1 fish/m3) and decreased linearly as fish number at harvest increased. Mean chlorophyll a and nitrite-nitrogen concentrations ranged from 803-1,460 mg/m3 and 0.056-0.390 mg/L, respectively, and were unrelated to stocking rate. Mean nitrate-nitrogen concentrations ranged from 7.19-28.82 mg/L and increased as stocking rate increased. Mean ammonia-nitrogen concentrations ranged from 0.01-0.35 mg/L and were unrelated to stocking rate. Microbial analysis of raceway water samples one week before harvest showed approximately 500,000 cfu/mL heterotrophic aerobic bacteria and 1,000-10,000 cfu/mL of nitrifying bacteria. Results of Trial 1 indicate that catfish survive and grow in a microbial-based production system, but further research is necessary to determine the full feasibility of this production system.