292 FISH HATCHERY MANAGEMENT 



diseases. The Fish and Wildlife Service Disease Control Program serves as 

 a model for other governmental agencies. 



During an on-site disease inspection at a hatchery, the fish health in- 

 spector will collect random samples of fish tissue to be sent to a laboratory 

 for analysis. The tests to be conducted will vary according to the type of 

 certification requested and should follow the standardized procedures of 

 the Fish Health Section of the American Fisheries Society (Procedures for the 

 Detection and Identification of Fish Pathogens). 



The inspector takes tissues from a specified number of fish from each 

 population at the hatchery. In most cases, each fish sampled must be 

 killed. The minimum sample size from each population will follow a statist- 

 ical plan that provides a 95% confidence for detecting a disease agent with 

 an incidence of infection at or greater than 2 or 5% (Table 38). 



The sample sizes represent the minimum acceptable number. In situa- 

 tions where the presence of a disease agent is suspected strongly, larger 

 samples may be necessary and taken at the discretion of the inspector. The 

 method of collecting subsamples from rearing units to obtain a representa- 

 tive sample also is left to the inspector. 



For all fish except those being inspected for whirling disease, the sample 

 population is determined on the basis of hatchery variables such as species, 

 age, and water source. Generally, two egg shipments of fall- spawning rain- 

 bow trout from the same hatchery received in September and December 

 are considered as a single population; similarly, all spring-spawning rain- 

 bow trout from the same source would be another population. However, 



Table 38. the minimum sample sizes for fish-disease inspections, accord- 

 ing TO the number of fish in the population that will allow a disease 



TO BE detected IF IT OCCURS IN 2". OR 5"n OF THE POPULATION. 



