John A. Hargreaves

Environmental Best Management Practices for Aquaculture

Contributors. Preface. United States Aquaculture Society Preface. 1. Aquaculture and the Environment in the United States ( Craig S. Tucker, John A. Hargreaves, and Claude E. Boyd ). 2. The Role of Better Management Practices in Environmental Management ( Jason W. Clay ). 3. Better Management Practices in International Aquaculture ( Claude E. Boyd ). 4. Best Management Practice Programs and Initiatives in the United States ( Gary L. Jensen and Paul W. Zajicek ). 5. Development, Implementation, and Verification of Better Management Practices for Aquaculture ( Claude E. Boyd, Paul W. Zajicek, John A. Hargreaves, and Gary L. Jensen ). 6. Better Management Practices for Freshwater Pond Aquaculture ( Craig S. Tucker, John A. Hargreaves, and Claude E. Boyd ). 7. Better Management Practices for Marine Shrimp Aquaculture ( Claude E. Boyd ). 8. Better Management Practices for Net-Pen Aquaculture ( Sebastian M. Belle and Colin E. Nash ). 9. Better Management Practices for Flow-through Aquaculture Systems ( Gary Fornshell and Jeffrey M. Hinshaw ). 10. Better Management Practices for Recirculating Aquaculture Systems ( Steven T. Summerfelt and Brian J. Vinci ). 11. Better Management Practices for Bivalve Molluscan Aquaculture ( R. LeRoy Creswell and Aaron A. McNevin ). 12. Fish Health Management and the Environment ( Scott E. LaPatra and John R. MacMillan ). 13. Economics of Aquaculture Better Management Practices ( Carole R. Engle and G. Ada Wossink ). Appendices. Index.

A simulation model of ammonia dynamics in commerical catfish ponds in the southeastern United States

Abstract A mechanistic model was developed to simulate annual variation of ammonia concentration in commercial (levee-type) catfish ponds in the southeastern United States. A simple mass balance approach was used to describe ammonia concentration as the balance (residual) between nitrogen sources and sinks. Two primary source processes (fish excretion and sediment diffusion) and two primary sink processes (phytoplankton uptake and nitrification) were considered. Model output predicted that 25–33% of ammonia production was derived from sediment diffusion. The rate of phytoplankton uptake of N was expected to exceed nitrification during the growing season (April-October), whereas nitrification rate would exceed phytoplankton uptake during cooler months. Nitrification rate was bimodally distributed, with peaks in spring and fall, and was related to the interaction between ammonia concentration and water temperature. Sensitivity analysis of model parameters indicated that average annual ammonia concentration was most sensitive to the partition of nitrogenous excretion between solid and dissolved fractions, average feeding rate, and phytoplankton specific uptake rate. Average annual ammonia concentration was relatively insensitive to changes in feed conversion. Model output and results of the sensitivity analysis provide insight into the magnitude and relative importance of the processes affecting ammonia transformations in commercial catfish ponds and offer possibilities for the most effective management intervention.

1 Industry development

Publisher Summary This chapter focuses on the biology and culture of channel catfish Ictalurus punctatus —the most important aquaculture species in the United States. The channel catfish is a member of the family Ictaluridae—the North American catfishes—which comprises seven genera and at least 45 species. The blue catfish Ictalurus furcatus is a close relative of channel catfish and has considerable potential for exploitation as a farmed species in its own right. The main interest in blue catfish, however, stems from its potential contribution to the genotype of hybrids with channel catfish. Blue catfish generally resemble channel catfish, although blue catfish have a smaller head and a longer, less rounded anal fin. Blue catfish grow slower than channel catfish during the first two years of life under culture conditions, although strain effects are important and some strains of blue catfish grow faster than many strains of channel catfish. Many are fine table fish, but the channel catfish accounts for virtually all of the commercial food-fish production in the United States. The chapter also provides a brief summary of other ictalurid catfishes that have been considered for aquaculture from time to time. The prominent role of research is emphasized as a factor contributing to successful industry development.

10 Pond water quality

Publisher Summary Catfish farmers should use high-quality water to fill ponds and then manage water quality within the tolerance limits to optimize growth, survival, and feed conversion. Finding good quality water to fill ponds is relatively easy, but maintaining environmental conditions within the tolerance limits of catfish is challenging. Historically, the technical development of catfish farming in static ponds has been characterized by increasing intensification. The emergence of yield limits as catfish production has intensified can be attributed in part to water quality degradation associated with eutrophication. Thus, the need for research on water quality dynamics and practical management of water quality problems is clear. Research on water quality in aquaculture ponds has provided tangible benefits to catfish producers. Specifically, research on pond aeration systems and the discovery that common salt can be used to manage nitrite toxicity have facilitated the intensification of catfish production.

Dietary Phosphorus Modifications in Practical Feeds Do Not Affect Waterborne Phosphorus Concentrations and Phytoplankton Abundance in Channel Catfish Ponds

Abstract We measured concentrations of soluble reactive phosphorus, total phosphorus, and chlorophyll a in 0.04-ha ponds containing channel catfish Ictalurus punctatus during three feeding trials to evaluate the effect of dietary phosphorus modifications on water quality and the potential discharge of phosphorus and organic matter in pond effluents. In experiment 1, a basal diet with 0.20% available phosphorus was compared with diets supplemented with 0.5% or 1.0% dicalcium phosphate to provide 0.27% or 0.35% available phosphorus. In experiment 2, fish were fed diets supplemented with either dicalcium phosphate or defluorinated rock phosphate to contain 0.40% available phosphorus. In experiment 3, fish were fed one of three diets containing 250 or 500 phytase units of phytase per kilogram (0.27% available phosphorus) or 0.75% dicalcium phosphate (0.39% available phosphorus). Husbandry practices in all three experiments were typical of commercial culture conditions. Quantitative and qualitative modificatio...

22 Environmental issues

Publisher Summary Aquaculture can have negative environmental impacts, so concerns related to the environmental impacts of agriculture have now been extended to aquaculture. Most of the concerns over the environmental impacts of aquaculture were initially directed at marine shrimp farming and net-pen culture of salmon in the coastal and marine environment. In addition to complaints over negative environmental impacts, questions were raised about food safety and social injustices arising from aquaculture. Major environmental impacts that have been attributed to aquaculture include wetland destruction, conversion of agricultural land to ponds, water pollution, loss of biodiversity, excessive use of water, introduction of non-native species, use of toxic or bioaccumulative chemicals, wasteful use offish meal in feeds, and inefficient use of other natural resources. The major issue related to food safety has been use of antibiotics, drugs, and other chemicals for treating aquatic animal diseases. Other issues include contamination of aquaculture products with pesticides and other organic compounds. This chapter discusses several environmental issues in catfish farming in the United States and considers strategies that are employed to improve the environmental performance of catfish culture in ponds. The environmental impact of catfish farming is the possibility of water pollution resulting from pond effluents. The chapter thus addresses catfish pond effluents and other concerns—food safety, threats to biodiversity, and social concerns.