Cowichan Adult Chinook Enumeration methodology change

Adult Chinook returning to the Cowichan River have been enumerated using a counting fence since 1988 as a PSC indicator stock. The operation of the fence has been met with various technical/environmental challenges over the years resulting in site relocation as well as several re-builds. Cowichan Tribes has expressed concern regarding negative impacts to fish including migration delays and physical damage.  This proposal will investigate the use of PIT tags as an alternative method for estimating escapement.   Specifically, tags returning from juvenile deployments will be expanded based on a mark rate from a sub-sample of the population.  PSC funding will be used to both deploy tags in juveniles as well as to support an estimate of mark rate in the adult population.

The use of PIT tags will also allow additional information to be collected including downstream survival of juveniles, marine survival estimates, age class composition and migration time.  Additionally, predation investigations may also be supported as PIT tags have been detected inside other animals and in scat within the surrounding area.