Across Washington State’s forested landscape, fish barriers exist where road crossings over streams were constructed during previous management and regulatory regimes that did not require passability. However, industrial and state forest landowners have been required to inventory and address these blockages since 2001 (WAC 222-24-051). While significant efforts and financial investments continue to be made to identify and correct fish passage barriers on forest lands, less has been done to evaluate and document the biological response to such efforts (Pess et al. 2005; Cocchiglia et al. 2012).
When a fish-blocking culvert is replaced or removed, it is generally assumed that fish will migrate upstream to utilize the newly accessible habitat within a short period of time. This assumption is seldom tested regarding resident trout populations in Washington state and has been a source of contention amongst various stakeholder groups due to its implications to land management decisions and protection standards.
Are resident trout mobile enough to quickly take advantage of newly opened habitat? In a study in Southeast Alaska, Bryant et al. (1999) suggest that rapid colonization by anadromous salmonids is a life history strategy to take advantage of newly accessible habitat as it becomes available (e.g., retreating glacial valleys). Could the same be true for resident trout? Gerking (1959) explained why individual fish of different species tended to stay in a small area over an extended period of time while more recent work by Schrank et al. (2004) shows inland cutthroat trout to be quite mobile and exploratory.
Olis, M., Marks, D., Veldhuisen, C. and Shattuck, B., 2018. Resident Trout Response to Barrier Culvert Removal in the Northwest Washington Cascades. Skagit River System Cooperative, La Conner, WA. pp. 35.
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