PRODUCTION PRACTICES
AND WATER QUALITY

Scientists:
Charles C. Mischke
Craig Tucker

Support Personnel:
Margaret Dennis, Research Associate III
A. Wayne Jobe, Fishery Technician
Sue Kingsbury, Research Associate III

Efficient and profitable aquaculture depends on providing a suitable environment in which fish can grow. The goal of production and water quality research at the National Warmwater Aquaculture Center is to provide a suitable culture environment for fish growth by understanding the ecological processes operating in catfish ponds and devising management practices that allow some control over those processes.

One of the most costly environmental problems in catfish farming is the development of undesirable "off-flavors" in fish. Off-flavors are caused by odor-producing blue-green algae that periodically grow in catfish ponds. Off-flavored fish are unmarketable until flavor quality improves, causing a severe economic hardship on farmers. Researchers at NWAC have developed safe, inexpensive treatments for algae-related off-flavors with the algicides copper sulfate and diuron. These treatments have been widely adopted by the catfish industry and reduce the incidence of undesirable flavors by over 50% with benefit to cost ratios of approximately 40 to1.

Zooplankton are important contributors to the nutrition of larval and juvenile fish, but no one has studied the ecology of zooplankton communities in catfish ponds. We have shown zooplankton to be highly nutritious and actively sought by catfish fry. Methods have been developed to assess zooplankton populations in fry ponds and fertilize ponds for optimum zooplankton production. These methods have been adopted by progressive catfish farmers with significant improvements in fingerling growth and survival.

All farming should be conducted to minimize impacts on the environment. Researchers at NWAC have developed simple management practices that reduce the amount of waste produced by catfish ponds and decrease the volume of water discharged from ponds. Most of these practices are simply part of good overall farm management, and can be implemented with little or no extra expense or labor. Adoption of these practices will allow catfish farms to be operated with minimal impact on the environment.

Other areas of interest include development of novel pond production systems, studies of basic pond limnology, interactions of fish health and water quality, and evaluation of pond aeration systems.