284 FISH HATCHERY MANAGEMENT 



Facility Decontamination 



In recent years, as fish production has increased at comparatively high 

 costs, prevention and control of diseases have assumed major importance. 

 Some diseases are controlled quite easily. For those that presently cannot 

 be treated, the only successful control is complete elimination of all infect- 

 ed fish from a hatchery, thorough decontamination of the facility, develop- 

 ment of a new stock of disease- free fish, and maintenance of disease- free 

 conditions throughout all future operations. Hatchery decontamination has 

 been successful in removing corynebacteria and IPN virus in many cases. 

 However, this method is practical only at those hatcheries having a con- 

 trolled water supply originating in wells or springs that can be kept free of 

 fish. 



ELIMINATION OF FISH 



During decontamination, all dead fish should be destroyed by deep burial 

 and covered with lime. The burial grounds should be so located that leach- 

 ing cannot recontaminate the hatchery water supply. All stray fish left in 

 pipelines will be destroyed by chlorine, but it is important that their car- 

 casses be retrieved and destroyed. 



PRELIMINARY OPERATIONS 



Before chemical decontamination of the hatchery is started, several prelimi- 

 nary operations are necessary. The capacities of all raceways and troughs 

 are measured accurately. The areas of all floor surfaces in the buildings are 

 calculated, and allowance is made for 3 inches of solution on all floors. 

 Then, the quantity of sodium hypochlorite needed to fill these volumes 

 with a 200 parts per million solution is computed. It the chlorine solution 

 will enter fish- bearing waters after leaving the hatchery, it will have to be 

 neutralized. Commercial sodium thiosulfate, used at the rate of 5.6 grams 

 for each gallon of 200 parts per million chlorine solution, will suffice. 



All loose equipment should be brought from storage rooms, scrubbed 

 thoroughly with warm water and soap, and left near a raceway for later 

 decontamination. Such equipment includes buckets, pans, small troughs, 

 tubs, screens, seines, and extra splash boards. During this operation, any 

 worn-out equipment should be burned or otherwise destroyed. Hatching 

 and rearing troughs should be scrubbed clean. The sidewalls of all race- 

 ways should be scrubbed and the bottom raked. Particular attention should 

 be given to removing any remaining fish food, pond scum, or other organic 

 substances. 



