AND WATER QUALITY
Charles C. Mischke
A. Wayne Jobe, Fishery Technician
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.