Management of water quality and effluents from aquacultural systems

Linda Benedict, Romaire, Robert P.  |  4/17/2009 12:02:27 AM

Profitable aquaculture depends on good water quality. Physiologically, aquatic animals respond more intensely to their environment than do terrestrial animals. The stress of poor water can lead to disease and poor nutrition and growth of cultivated aquatic animals.

LSU Agricultural Center scientists are addressing several issues related to water quality management in crawfish and channel catfish aquaculture. At the Rice Research Station in Crowley, scientists are studying the effects of long-term exposure of low oxygen on growth and mortality of red swamp crawfish. At the Aquaculture Research Station in Baton Rouge, management of algal populations for water quality improvement and off-flavor control in channel catfish ponds is being investigated in several projects which include polyculture with algal-feeding fishes, such as threadfin shad and tilapia; reducing odorous populations of blue-green algae by adding salt or trace minerals; and assessment of the partitioned aquaculture system.

In recent years, concerns about agriculture’s effect on the environment, particularly related to non-point sources of pollution on stream and lake water, have been raised. The LSU Agricultural Center hosted a workshop in July of 1999 on “Agricultural Water Quality Issues for the 21st Century” to review, discuss and begin strategic planning on issues related to federally mandated requirements to protect the quality of Louisiana’s surface water resources. The federal Clean Water Act of 1972 (formerly known as the Federal Water Pollution Control Act) and subsequent amendments enacted in the past decade require that the nation’s streams, rivers and lakes be sufficiently clean to be fish able and swimmable by a target date near the year 2010. Enforcement of the Clean Water Act is given to the individual states by the U.S. Environmental Protection Agency.
Effluents from aquacultural operations are released into streams and rivers during heavy rainfall, when harvesting fish, to accommodate reproductive cycles of the cultured animal (for example, draining crawfish ponds to stimulate burrowing) or to maintain acceptable water quality in the culture system. Many of the state’s aquacultural producers, particularly crawfish farmers, use streams and rivers as their principal water source.

In the 1970s, most states did little to regulate aquacultural effluent discharge, mostly because aquaculture was considered too small an industry to have a significant impact on the environment. But growth in the nation’s aquaculture industry, coupled with provisions of the federal Clean Water Action Plan of 1998 and legal action against the EPA by non-governmental organizations, necessitates that Best Management Practices (BMPs) for agricultural commodities, including aquaculture, be developed and implemented. Failure to address these needs could constrain future growth and development of Louisiana’s aquaculture industry.

In April of 1999, a three-year regional projecton “Management of Aquacultural Effuents from Ponds”  was funded by the Southern Regional Aquaculture Center (SRAC). This study follows a three-year project completed in 1994,  also funded by SRAC, in which 16 scientists representing 10 universities, including the LSU AgCenter, cooperated to characterize effluents from commercial aquaculture operations in the South, including commercial crawfish farms in Louisiana.

The present study, which includes participation of aquacultural scientists froms even universities and one state agency, will provide more detailed data on effluent quality and quantity from major aquacultural industries in the South, including catfish, crawfish, bait fish, hybrid striped bass and marine shrimp. Emphasis will be placed on determining the amount of suspended solids and phosphorus discharged during intentional (for example, draining at harvest) and non-intentional (storage overflow during rainfall) effluent releases and their impact on receiving waters. Based on existing information, supplemented by the project findings, a comprehensive set of general BMPs that can be implemented to reduce the environmental effects of pond aquaculture will be developed. Supplemental BMPs for various pond cultured species in the southern region will be formulated, too. As in the previous study, LSU Ag Center scientists will have responsibility for crawfish aquaculture.
From data generated to date, the best approach to managing effluents from aquaculture is (1) to reduce the amount of waste produced in the pond by using high quality feed and efficient feeding practices and (2) to decrease the volume of water discharged by minimizing water exchange, reusing water  for several production cycles and maintaining enough storage volume in ponds to prevent rainfall overflow.

Louisiana aquaculture producers can be assured that AgCenter scientists will continue research and extension programs to develop practical, cost-effective solutions to management of pond effluents to comply with federal and state regulatory requirements, protect the environment and sustain profitability.

Robert P. Romaire, Resident Director and Professor, Aquaculture Research Station, LSU Agricultural Center, Baton Rouge, La.

(This article was published in the fall 1999 issue of Louisiana Agriculture.)

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