- Select stocking and feeding rates that do not exceed the assimilation capacity of ponds;
- Feeds should be of high quality, water stable, and contain no more nitrogen and phosphorus than necessary;
- Apply feeds conservatively to avoid overfeeding and to assure that as much of the feed is consumed as possible;
- Do not use water exchange or reduce water exchange rates as much as possible;
- In intensive aquaculture, apply enough mechanical aeration to prevent chronically low dissolved oxygen concentration and to promote nitrification and other aerobic, natural water purification processes;
- Provide storage volume for heavy rainfall to minimize storm overflow;
- Deep water release structures should not be installed in ponds, for they discharge lower quality water from near pond bottoms;
- Where possible, seine-harvest fish without partially or completely draining ponds;
- Where possible, discharge pond draining effluent through a settling basin or a vegetated ditch; and
- Reuse water where possible.
As for erosion control BMPs, this selection of BMPs for nutrient management is only a partial list. Many of the presentations of aquaculture BMPs are simply lists of suggested practices as in the examples above.
The presentation of BMPs as brief statements leaves the producer to decide upon the method of implementation. It is desirable to present the BMPs in a document that contains suggestions, guidelines, and specifications for implementation. For example, the GAA prepared a series of codes of practices for use by shrimp farmers (Boyd, 1999).
The codes of practices deal with nine selected topics, e.g., mangroves, feed practices, effluents and solid wastes, etc., each with a list of suggested BMPs. The GAA also prepared an implementation document that leads the producer through the steps necessary to execute the BMPs.
The Alabama Catfish Producers Association, Auburn University, Alabama Department of Environmental Management (ADEM), and the United States Department of Agriculture Natural Resources Conservation Service (USDA NRCS) cooperated to develop BMPs for channel catfish farming in Alabama (Boyd and Hulcher, 2001).
These BMPs were presented as a series of 15 NRCS Alabama Conservation Practice Guide Sheets (Auburn University and Natural Resources Conservation Service, 2002). Each guide sheet provides a discussion of the objectives of the practices, a list of the practices, implementation notes, and references.
The BMPs will be maintained by NRCS, and ADEM will refer to the BMPs as necessary in their rules for regulation of aquaculture effluents in Alabama. The Florida Department of Agriculture and Consumer Services also made a BMP document for aquaculture that includes guidelines for implementation. Many codes of conduct and practices programs for aquaculture, however, do not include specific suggestions for implementation of BMPs (Boyd et al., 2001).
The use of BMPs as a basis for formal governmental regulation of aquaculture effluents in developing countries appears more feasible than application of effluent standards and permits. Although it would require considerable effort to enforce a regulatory system based on BMPs, the amount of resources, manpower, and expertise would be much less than for enforcement of effluent permits with water quality criteria.
It should be possible by an annual inspection by a qualified professional to determine if BMPs have been implemented on a farm. Of course, specific rules must be established about the actions to be taken in case of non-compliance, just as is necessary in enforcement of effluent permits.
Author:
Claude E. Boyd
