Assessment of the Geographic Distribution for Coho Salmon in Tributaries of the Lower Klamath River

This project will assess juvenile Coho and other salmonid species spatial distribution and density throughout the Lower Klamath tributaries. The proposed project would survey the entire sampling universe (22 tributaries, 69 reaches) that was built for the Lower Klamath region and contains all the habitat historically occupied by Coho Salmon. Including the entire sampling frame addresses a major problem of the past spawner survey methodology where randomly selected reaches primarily consisted of marginal habitat. Assessing adult populations required repeat surveys from December-February that reduced the number of reaches that could be surveyed in a given year (20 reaches). Determining spatial distribution for juvenile Coho Salmon only requires one survey in a given year and these are conducted in the low flow period during late summer and early fall. By only conducting a single survey it is possible to include the entire sampling universe in a given year. Juvenile Coho Salmon are more numerous than adults which greatly increases the probability of detecting the species in a given pool or reach. The reliability of a surveyor correctly identifying species is much greater for juvenile Coho Salmon than assigning species to observed redds.

The proposed methodology for assessing the spatial structure of Lower Klamath Coho Salmon is described in Garwood and Ricker (2014). Counts of juvenile Coho and other salmonid species will be conducted through snorkeling every other pool in each sampling reach. Every fourth pool will be snorkeled by another person to obtain observer efficiency estimates. Other information that will be collected during surveys includes pool surface area and large wood counts. Pool surface area and juvenile counts provide a density estimate that can be used to compare relative abundance among the survey reaches. Large wood counts can be used to identify areas for future restoration projects that include wood loading. Information on spatial structure, juvenile Coho Salmon density, and large wood counts are critical for making informed decisions on potential restoration projects in the Lower Klamath region. Current data on most lower Klamath tributaries is lacking since the last comprehensive survey of juvenile Coho Salmon in lower Klamath tributaries occurred over 20 years ago (Voight and Gale 1998).

Project Objective: To assess the geographical distribution of Coho Salmon in Lower Klamath River tributaries. Coho Salmon Oncorhynchus kisutch inhabiting the Lower Klamath Sub-Basin are an independent population within the Southern Oregon/Northern California Coast (SONCC) Evolutionarily Significant Unit (ESU). Coho Salmon in the SONCC ESU are listed as threatened under both federal and state endangered species acts. To either delist a salmon species or change the status from threatened to endangered requires information on the abundance of populations in ESU’s over time. McElhany et al. (2000) developed the Viable Salmonid Population (VSP) framework to assess salmonid population viability within ESU’s. The VSP framework is based on four viability metrics that measure: abundance, productivity, spatial structure, and diversity. These metrics are the basis for assessing when a listed species has recovered. Currently, reliable information for a critical element of the VSP (spatial structure) within the Lower Klamath region is lacking and prevents National Marine Fisheries Service from making informed decisions on the status of this independent population.

As part of California Department of Fish and Wildlife’s (CDFW) Coastal Monitoring Program the Yurok Tribe collaborated with CDFW by conducting adult salmonid spawner surveys in lower Klamath tributaries during three years (2014/2015, 2015/2016/, 2016/2017). A primary purpose of these spawner surveys was to obtain information for the geographic distribution (spatial structure) of the Lower Klamath independent population of Coho Salmon. Results from these surveys yielded very few adult Coho Salmon observations during surveys for two main reasons: most of the reaches that were randomly drawn for surveys contained marginal habitat for Coho Salmon and although there are self-sustaining Coho Salmon in many Lower Klamath tributaries adult populations are small enough that they often escaped detection during surveys. In several tributaries of the lower Klamath (Blue, Ah Pah, and Terwer Creeks) no Coho Salmon redds were observed during spawner surveys. However, other surveys that sampled juvenile Coho Salmon during this same three-year period found juveniles to be widespread and relatively abundant. These juvenile observations indicate surveys conducted for juveniles would likely produce more reliable results for the spatial distribution of Lower Klamath Coho Salmon than the adult surveys produced. Project Benefit: To assess spatial distribution and densities of juvenile Coho in tributaries of the Lower Klamath River. Coho Salmon in the SONCC ESU are listed as threatened under both federal and state endangered species acts. To either delist a salmon species or change the status from threatened to endangered requires information on the abundance of populations in ESU’s over time. The development of VSP framework to assess salmonid population viability within ESU’s. The VSP framework is based on four viability metrics that measure: abundance, productivity, spatial structure, and diversity. These metrics are the basis for assessing when a listed species has recovered. This project will provide information for a critical element of the VSP (spatial structure) within the Lower Klamath region is lacking and prevents National Marine Fisheries Service from making informed decisions on the status of this independent population. Information on spatial structure, juvenile Coho Salmon density are critical for making informed decisions on potential restoration projects in the Lower Klamath region. Priority 2