Comprehensive surveys are needed to identify fish use on all non-federal forest streams. Such an effort would require a number of years to complete and a significant financial investment. The purpose of this section of the Forest Practices Board Manual is to provide guidelines for determining fish use for water typing purposes. A uniform stream survey protocol is needed so that data on fish presence is collected in a uniform manner and so that affected landowners and other interests can provide data to disprove the presumption of presence in a manner that provides credible data to support proof of absence. Interested parties will continue to work on the completion of ground-truthing the Washington State's rivers and streams to accurately depict the fish resources present.
Many factors can influence the extent and distribution of fish species in the watershed.
Depressed stocks will fail to fill all the available habitat niches. Likewise, drought or flood years may alter how species occupy the habitat. Fish populations may be locally extirpated from stream channels due to mass wasting and downstream scouring that can require years before even partial recovery begins. There are many visual methods such as walking the stream bank and visually observing fish, snorkeling, feeding, and hook and line sampling to show presence at a particular site along a stream segment. Projecting the extent of fish utilization upstream dependent on observed stream habitat parameters may be as dependent on professional judgement as on measurable physical criteria.