FISH HEALTH MANAGEMENT 289 



The mass inoculation method works well with fish in the 5-25 gram 

 range, and individual operators are able to vaccinate 500-1,000 fish per 

 hour. Cost of the technique seems reasonable but the number of fish that 

 can be treated is limited by the manpower available for short-term employ- 

 ment and by the size of the inoculating tables. 



The infiltration method (hyperosmotic immersion) allows vaccination of 

 up to 9,000 fish (1,000 to the pound) quickly and safely in approximately 4 

 minutes. The method utilizes a specially prepared buffered hyperosmotic 

 solution. Through osmosis, fluid is drawn from the fish body during its im- 

 mersion in the buffered prevaccination solution. The fish are then placed 

 into a commercially prepared vaccine that replenishes the body fluids and 

 simultaneously diffuses the vaccine or bacterin into the fish. 



Fish are spray vaccinated by removing them briefly from the water and 

 spraying them with a vaccine from a sand-blasting spray gun. Antigenicity 

 of the preparations is markedly enhanced by the addition of bentonite, an 

 absorbent. Spray vaccination against vibriosis protected coho salmon for at 

 least 125 days. Most importantly, the method appears, like the injection 

 method, to be a successful delivery system for all four bacterins tested (two 

 Vibrio species, Aeromonas salmonicida, and a kidney disease bacterium). 



In 1976, two bacterins were licensed for sale and distribution by the 

 United States Department of Agriculture. These products are enteric red- 

 mouth and Vibrio anguillarum bacterins. 



Fish Disease Policies and Regulations 



Current disease-control programs are administered by the Colorado River 

 Wildlife Council, the Great Lakes Fishery Commission, the United States 

 Fish and Wildlife Service, numerous states, and several foreign countries. 

 Most of the state and national programs include important regulations to 

 restrict certain diseases. Very few programs have regulations requiring des- 

 truction of diseased fish and only California has provisions for indemnifica- 

 tion of losses sustained in eradication efforts. 



The last 20 years have seen a gradual change in disease control emphasis 

 from treatment to prevention. International, federal, and state legislation 

 have been passed to minimize the spread of certain contagious diseases of 

 fish. The use of legal and voluntary restrictions on the transportation of 

 diseased plants and animals, including fish, is not new. In the United 

 States, the Department of Agriculture has an extensive organization for the 

 reporting and eradication of certain plant and animal diseases. Unfor- 

 tunately, this program does not cover fish. Both compulsory and voluntary 

 regulations have been used to fight diseases in other animals. Some disease 

 eradication methods are severe, such as the prompt destruction of entire 



