Human-made fish passage barriers have been identified as one of the leading contributors to aquatic habitat fragmentation (Sheer & Steel 2006). Salmonids and aquatic life rely on complex, continuous habitat to support population health, abundance, and reproductive success (Flitcroft et al. 2019). Therefore, identifying and understanding the impact of fish passage barriers is a critical step to improving aquatic habitat of salmonids and other aquatic life in the Skagit River Basin (Beamer et a. 2005). Through industrialization and urbanization, areas that once had booming runs of salmon are now struggling to maintain stable populations (Yeakley & Hughes 2014). Culverts have not always been designed with consideration of fish use and may not allow adequate conditions for the migration of anadromous fish and other aquatic species. Adult and juvenile salmonids need unimpeded access to upstream and downstream habitat for foraging, rearing, predator and thermal refuge, and spawning gravels (SWC 2020/Flitcroft et al. 2019). Connecting previously fragmented habitats, therefore increasing habitat area and capacity of rearing and spawning, has been shown to have a positive effect on salmonid abundance and population success (O’Neal et al. 2024). Because of the issues listed above, efforts to record and update the current conditions of water crossings and culverts are a priority in all streams and rivers with fish use in the Skagit River Basin (Beamer et al. 2005).
