The project will identify the range and effective size of genetically isolated endemic cutthroat populations. The Westslope cutthroat are ESA-listed, and coastal cutthroat are a step away. Due to the recent stream typing work, the team has thus far identified 8 geographically isolated cutthroat populations and we need to determine their effective sizes and whether there is any gene flow between them, or with mainland populations. This would be the next step towards establishing WRIA2 as an ESU for cutthroat.

Our ongoing watershed inventory has thus far found coastal cutthroat in five WRIA2 streams. After mapping barriers in each stream, monitoring pools with juveniles or adults, and conducting spawner surveys, we conclude that there are as many as 11 distinct cutthroat spawning populations. Many are isolated from the sea by barriers such as waterfalls and ponds; others occupy reaches separated from one another by weirs, falls or culverts posing at least partial barriers to migration.

We will use nuclear genetic markers to assess the genetic isolation of WRIA2 cutthroat stocks; their ancestral relationships with one another and mainland populations; possible hybridization of native cutthroat with introduced rainbow/steelhead in WRIA2; and whether adaptation to extreme conditions (high temperature, low oxygen) has played a role in the genetic differentiation of WRIA2 cutthroat. Addressing these issues through population genetics is a priority in WRIA2's three-year work plan.

Results can be used to establish WRIA2 priorities for habitat protection and restoration in at least three streams where restoration projects are in the design stage. Populations that have long been genetically isolated from mainland stocks and from other WRIA2 stocks are probably locally adapted and should have highest priority for protection. Populations that appear to be physically isolated without significant genetic isolation are probably the result of artificial barriers that should be removed to restore habitat connectivity.