Abstract

Since 1997 the Wisconsin Department of Agriculture, Trade and Consumer Protection (WDATCP) has developed a regulatory fish health program that creates one set of health standards for both private fish farms and government fish hatcheries. The WDATCP began by working very closely with fish farmers, private veterinary practitioners, and government fish hatchery staff.

The program includes registration of fish farms, issuance of fish import permits, certification of veterinarians, and rules for health standards for fish introduced into public waters. A key component of the Wisconsin fish health program's success has been the close working relationship between WDATCP and fish farmers, and veterinarians.

Pathogens are an inherent feature among both wild and captive populations of fish. Multiple factors, such as the environment and the condition of the fish, affect whether fish will become ill, or diseased. Infection and disease are not the same. Infection is the invasion of a host by a pathogenic organism; this may or may not result in disease. Disease is the loss of a health condition and has characteristic signs and pattern of death loss (mortality) with a population.

Import of fish, naturally and by man, presents the greatest risk of disease spread and pathogen introduction. Fish migrate naturally, and may travel from infected regions to un-infected regions. Commerce of live fish and fish eggs is a major economic activity. The risk of disease spread and pathogen introduction is greatest in hatcheries that receive fish from many regions and stock most widely.

Aquaculture, state-supported and private, can impact fish populations in public waters. This can occur by disease spread or amplification of pathogens. Whether a hatchery is state-supported or private the fish health standards must be uniform and science-based.

Conversely, pathogen transmission from fish in public waters can adversely affect cultured species. The health status of broodfish and forage fish acquired from the wild and introduced into hatcheries should be subject to stringent health assessments. Unintentional introduction of infected fish or fish pathogens can occur from many sources, including fish entering in surface water, and birds and aquatic organisms harboring infective material. Hatcheries should employ appropriate measures to reduce the risk of infected aquatic organisms entering hatcheries.

The risk of introducing disease depends in large part on the type of aquaculture facility (recirculating, raceway, pond, net-pen), the health management practices, and stocking practices. The greater the level of health assessments and disease testing, the lower the risk of disease.

Hatcheries that stock public and private waters have an increased risk of introducing fish diseases compared to hatcheries that do not move live fish off of their hatchery.

We lack sufficient knowledge of the current distribution of pathogens in the North Central U.S., factors affecting pathogen transmission, associated risks of various diseases to fish populations, and management strategies to minimize and avoid pathogen impacts in aquaculture and public waters. In general, we have more information on diseases of trout and salmon as opposed to other species. However, recently we have increasing information on diseases of many species including channel catfish, yellow perch, largemouth bass, and lake sturgeon.

Increased attention to surveillance and monitoring of fish diseases is needed in our region. All species of fish must be considered when developing laws governing fish health. The costs and benefits of increased fish health efforts should be investigated, and be accompanied by efforts to educate producers and consumers.

The U.S. does not have official national standards for fish health. Fish health regulations in our region are a patchwork of state regulations. There is no single authority on fish health standards for our region. Fish health standards vary significantly from state to state. Some states have two sets of standards, one for state-supported aquaculture, the other, generally more stringent for private aquaculture.

Legal authority for state fish health standards resides in agriculture agencies or resource agencies. Federal health standards apply to international movement of fish and are administered by the U.S. Department of Agriculture or the U.S. Fish & Wildlife Service.

Acknowledgements

The author is grateful to Dr. Robert Ehlenfeldt, and the staff at Wisconsin's Division of Animal Health for their work on fish health.

References

1.  American Veterinary Medical Association, Policy: Aquatic Animal Health and Control Programs(1999)

2.  Wisconsin Department of Agriculture, Trade & Consumer Protection. 2004. Fish Health. Online version, http://www.datcp.state.wi.us/ah/agriculture/animals/aqua/health.