Dr. Jerri Bartholomew (OSU Microbiology) in collaboration with the Bureau of Reclamation are using "sentinel" fish to detect pathogens in aquatic ecosystems.  Cages of live, pathogen free fish, are placed in particular locations at different times of the year.  After 3-7 days of exposure, the fish are transported to the AAHL where they are held in clean water at selected temperatures and monitored daily for signs of disease.  Sentinel fish can alert us to where and when certain pathogens are present, and which fish species/stocks are susceptible to different pathogens.

https://microbiology.oregonstate.edu/deschutes-river