Challenges and Opportunities to Apply Process-Based Restoration at Scales Appropriate to Anadromous Fishes
Kris M. Homel, Chris M. Lorion, and Benjamin J. Clemens
Abstract—Habitat restoration in streams is critical to recovery of imperiled fishes. In the Pacific Northwest of North America, stream habitat restoration has focused primarily on anadromous salmonids Oncorhynchus spp. listed under the Endangered Species Act. Substantial restoration efforts have focused on the Oregon Coast evolutionary significant unit of Coho Salmon O. kisutch. However, many of these efforts have been local in scale (i.e., particular reaches within relatively small streams, high up in watersheds) and do not address habitat-forming processes at the watershed scale. Other anadromous species such as Chum Salmon O. keta and Pacific Lamprey Entosphenus tridentatus that co-occur in these watersheds are rarely targeted in habitat restoration yet are thought to benefit from restoration efforts for Coho Salmon. However, Chum Salmon and Pacific Lamprey tend to occur lower in watersheds than Coho Salmon, inhabit freshwater for different periods of time, and are therefore challenged by different limiting factors. As a result, benefits from restoration efforts for Coho Salmon may not be fully realized by Chum Salmon and Pacific Lamprey. Mounting evidence suggests that process-based restoration may yield substantial biological dividends for anadromous fishes. Although process-based restoration is still an area of active research, it does possess a stronger and more holistic conceptual foundation than restoration strategies aimed at creating particular channel forms. Process-based restoration addresses the geological, physical, chemical, climatic, and ecological processes that interact to form habitat mosaics to which anadromous fishes have adapted. Understanding and working within these processes throughout entire watersheds and downstream into the estuary has the potential to benefit multiple anadromous fishes and substantially improve the ecological functions of watersheds. We explore the range of habitat relationships expressed among three imperiled anadromous fishes—Coho Salmon, Chum Salmon, and Pacific Lamprey—and present case studies to illustrate the importance of implementing process-based restoration to address limiting factors in their freshwater habitats. We conclude by suggesting three main strategies to address restoration challenges and limitations: forming multidisciplinary collaborations of restoration practitioners, investing in education and outreach to build larger and more diverse constituencies, and developing spatial and organizational tools to expand restoration efforts to the watershed scale.