8010 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I T bl 10 B t h' f b k k d' 1997 a e . a c 102 success 0 razor ac suc ers spawne 10 Lot Hatch Success Hatch Date Number ofFish Imprinting (%) Chemical 9701 15 970427 363 Phenethyl 9702 20 970427 490 Alcohol 9703 10 970427 99 9704 1 970427 15 Average 11.5 Total 967 Problems Disease proved to be a problem at the facility. Columnaris broke out on May 14, 1997, in two tanks of fish (representing one family lot) that had just been PIT tagged. The timing of the outbreak suggested that infection occurred when the fish were PIT tagged. Once the pathogen was introduced into the hatchery, it proved difficult to isolate and eradicate. The bacteria spread and was ultimately responsible for more than 2,700 mortalities from four family lots. After the pathogen was correctly identified and appropriate treatment was applied, mortalities dropped and we have had no further outbreaks. Several treatments, including Formalin, salt, and Sparaquat 256 baths, were tried before an effective one was found. A combination of Chloramine T and Terramycin baths proved to be most effective. A sanitization procedure has been implemented to lessen the likelihood of outside infection in the future. The procedure includes sanitizing hands and shoes with Sparaquat 256 upon entering the hatchery, and regularly sanitizing the floor and equipment. Another problem was that the biofilter fails when chemical treatments (e.g., Sparaquat 256 or Chloramine T) or improper back-flushing kill the bacteria that live within the filter.. When the bacteria die, the filter is not able to convert ammonia and nitrite into nontoxic nitrate, creating toxic levels of both ammonia and nitrite. When the filter fails, feeding must be reduced or stopped until the bacteria get reestablished inside the filter. Once they are reestablished, feeding can be resumed gradually. Several actions can be taken to reduce the toxicity of ammonia and nitrite levels while the biofilter recovers. Carbon dioxide can be added to lower the pH of the water which decreases the toxicity of the ammonia. A product called Ammo-lock 2 can be added to the system to instantly detoxify ammonia. Salt can be added to the water, to lower the toxicity of the nitrite. The chloride ions from the salt join with the free nitrite ions which reduces toxicity to fish. -18-