274 1 ISH HATCHERY MANAGEMENT 



General Information on Chemicals 



Because many drugs and chemicals will be federally registered in the future 

 for use at fish hatcheries and historically have successfully controlled fish 

 diseases, much information is provided in the following section. However, 

 many have not been registered at this time by the United States Food and 

 Drug Administration for use with fishes; reference to unregistered drugs 

 and chemicals in this section and in other chapters of this book should not 

 be construed as approval or endorsement by the United States Fish and 

 Wildlife Service. In all cases where chemicals and drugs are discussed, 

 their registration status is indicated. 



Chemicals purchased for hatchery use should be of United States Phar- 

 maceutical (USP) grade, if possible, and stored in amber containers to 

 prevent deterioration by sunlight. The chemical formula should be on the 

 label. Treatment compounds must be stored as directed on the label, and 

 lids or caps always should be tight. If chemicals become abnormal in color, 

 texture, etc., they should be discarded. Poisonous chemicals should be han- 

 dled only with proper safety precautions. 



Antibacterial agents currently used to control bacterial infections in fish 

 include sulfonamides, nitrofurans, and antibiotics. The basic principle of 

 chemotherapy is one of selective toxicity. The drug must destroy or elimi- 

 nate the pathogen by either bactericidal or bacteriostatic action without 

 side reactions to the host. 



Treatment of some diseases, such as columnaris, ulcer disease, and furun- 

 culosis, requires the feeding of drugs. This is accomplished by mixing the 

 drug with the fish's food. The amount of drug to be fed is relatively small 

 and thorough mixing is necessary to insure proper distribution in the feed. 

 Fish should be hungry before medicated feed is administered; therefore, it 

 may be necessary to eliminate a prior feeding to insure that the treated 

 food is taken readily. 



With the development of dry diets it now is possible to buy medicated 

 feed containing the drug of choice. Fish of different sizes require use of 

 varying amounts of food and drug, and custom milling may be necessary in 

 order to deliver the proper dosage. 



When internal medication is begun, it should be maintained until the 

 prescribed treatment period has been completed. It takes approximately 3 

 days to build up an effective drug level within fish. To maintain the drug 

 level, the fish should receive only medicated food during the treatment 

 period. Generally, once the medication is started, it is continued for 10-12 

 days or until mortality returns to normal, then extended for at least 3 more 

 days. 



Drug combinations sometimes are more efficient than single drugs. The 

 combination of sulfamerazine and furazolidone (not registered by the Food 



