OPERATING THE HATCHERY 



( or for as lon^ as possible ) . Treat- 

 ments should be repeated at inter- 

 vals of several days, if needed. Use 

 of antibiotics in treatment of exter- 

 nal or internal diseases of fishes is 

 very recent, and the available in- 

 formation on this subject is scant. 

 Caution, therefore, is advised when 

 usin^ antibiotics. They should not 

 be used for prolonged periods of 

 time, (i. e. several weeks) be- 

 cause drug-resistant varieties of 

 pathogens may appear, and in such 

 cases antibiotics will become use- 

 less against them. 



Internal treatment 



In internal treatment, drugs are 

 given the fish by mouth with their 

 food, or in certain instances they 

 have to be introduced in capsules 

 directly to the stomach. Whenever 

 drugs are given with the food, it is 

 important to select a food of good 

 cohesion (or use medicated pellets) 

 which is readily taken by fish. This 

 is important, because if food is per- 

 mitted to remain in the water even 

 for a short time the drugs may 

 leach out. Drugs must be mixed 

 well with the food so that each fish 

 will get the ({uantity of drug pro- 

 portional to the amount of food 

 taken. Food should be fed judi- 

 ciously in quantities exactly re- 

 quired by the fish. If too much 

 food is given, both food and drug 

 will be wasted. If there is not 

 enough food given, the weakest fish, 

 which may need the drug the most, 

 will be deprived of it. Among the 

 drugs given orally are sulfonamides. 



antibiotics, calomel, carbarsone, and 

 kamala. 



Sulfonamides are most effective 

 in treatment of furunculosis, which 

 is a disease predominantly affecting 

 the salmonid fishes. Sometimes, 

 however, this disease may cause 

 losses among warm-water fishes. 

 Of the great variety of sulfonamide 

 drugs, those most frequently used 

 are sulfamerazine and sulfametha- 

 zine, with the possible addition of 

 sulfaguanidine. The effective dos- 

 age rate is 8 to 12 grams of sul- 

 famerazine daily per 100 pounds of 

 fish. Some workers have found 

 that replacement of one-third of 

 either of the first two sulfonamides, 

 with sulfaguanidine is somewhat 

 more effective. For best results, 

 treatment should start as early as 

 possible and be continued for about 

 2 weeks. In a recurrence of the 

 disease, treatment should be re- 

 peated. During the period of treat- 

 ment, only medicated food should 

 be fed to the treated fish. 



Calomel and carbarsone are effec- 

 tive in the treatment of intestinal 

 infections caused by one-celled ani- 

 mal parasites, like Octomitus. 

 Either one of these drugs should 

 be added at the rate of 1 gram to the 

 pound of food. Feeding of the 

 medicated food should be continued 

 for H days, and repeated when 

 needed. Kamala is used for treat- 

 ment of intestinal tapeworms in 

 fislies. It can be added to food at a 

 rate of 1 to 1.5 percent, or given in 

 capsules to large brood fishes, the 

 dosage being 0.1 gram for each 8 



56 



