Fish Hatchery Management - fisheries & aquaculture

FISH HAI'CHERY MANAGEMENTdiseases. The Fish and Wildlife Service Disease Control Proeram serves asa model for other governmental agencies.During an on-site disease inspection at a hatchery, the fish health inspectorwill collect random samples of fish tissue to be sent to a laboratoryfor analysis. The tests to be conducted will vary according to the type ofcertification requested and should follow the standardized procedures ofthe Fish Health Section of the American Fisheries Society (Procedures for theDetcrtion and Identification 0f Fish Pathogens).The inspector takes tissues from a specified number of fish from eachpopulation at the hatchery. In most cases, each fish sampled must bekilled. The minimum sample size from each population will follow a statisticalplan that provides a 95% confidence for detecting a disease agent withan incidence of infection at or greater than 2 or 50/o (Table 38).The sample sizes represent the minimum acceptable number. In situationswhere the presence of a disease agent is suspected strongly, largersamples may be necessary and taken at the discretion of the inspector. Themethod of collecting subsamples from rearing units to obtain a representativesample also is left to the inspector.For all fish except those being inspected for whirling disease, the samplepopulation is determined on the basis of hatchery variables such as species,age, and water source. Generally, two egg shipments of fall-spawning rainbowtrout from the same hatchery received in September and Decemberare considered as a single population; similarly, all spring-spawning rainbowtrout from the same source would be another population. However,TABLE 38. THE MINIMUM sAMpLE stzEs FoR FISH-DISEASE rNSpEcrIoNS. AccoRD-ING TO THE NUMBER OF FISH IN 'THE POPULAI'ION THAT WILL ALLOW A DISEASETO BE DETEC'I'ED IF IT OCCURS IN 2". OR 5'., OF THE POPULATION.SIZE OF SAMPLEPOPI]LA'I'ION SIZI 2 .. INCIDENCE ' ., INCII)ENCE50100250500l,000I,5002,0004,00010,000100,000 and larger4u77tt2l2ul3rlt42143t461471483444525557575u58585u