Project title: Chena River juvenile Chinook salmon large wood habitat mapping
Personnel Nate Cathcart (research technician - summer 2017) Funding source(s): U.S. Fish and Wildlife Service Project description: Large woody debris (e.g., logjams, rootwads; LWD) within the channel provide important rearing habitat for fishes, and especially for juvenile Chinook Salmon in interior Alaska rivers, including the Chena River. For juvenile salmon, LWD provides cover from predation, refuge from high flow velocities, and high quality habitat for invertebrate prey items. However, the distribution, abundance, and characteristics of LWD, particularly within stream reaches where juvenile Chinook Salmon are known to rear, have yet to be quantified in the Chena River basin. Our objectives are to, 1) georeference and make simple measurements of LWD along the entire rearing distribution of juvenile Chinook Salmon in the upper Chena River, and potential rearing distribution in the lower river, during June 2017, 2) relate characteristics (e.g., size, location, composition) of LWD to use (i.e., presence) by juvenile Chinook Salmon for a subset of LWD habitats identified in Objective 1 during July and August 2017, and 3) communicate the importance of LWD as juvenile Chinook Salmon habitat to the public. We will float the distribution of juvenile Chinook Salmon rearing habitats within the Chena River basin and make a rapid categorical estimate of LWD characteristics. The result of this survey will be digital map with the location and attributes of individual LWD throughout the juvenile rearing area. Subsequently, we will randomly select LWD to sample for occurrence and abundance of juvenile Chinook Salmon using snorkeling and videography. Finally, we will share the progress of our work with the community by hosting Chena River Chinook Salmon activities in conjunction with major community events along the riverfront in Fairbanks, create a website aimed at the local community to disseminate the results of our study, develop fact sheets about using LWD for streambank restoration by homeowners, and provide educational materials about Chinook Salmon in the Yukon River drainage. We measured habitat attributes (e.g., submerged area, formative fluvial process, etc.) for all logjams (N=429) and conducted fish snorkel counts for a randomly-selected subset (N=189) of logjams within the known distribution (283 stream-km) of juvenile Chinook Salmon rearing in the Chena River basin, Alaska, during summer 2017. Logjam density and potential wood recruits (i.e., downed trees) declined downstream (33 recruits/km, 6 logjams/km; 6 recruits/km; 0.3 logjams/km, respectively), particularly below Moose Creek Dam which is thought to intercept wood from the upper basin. Logjam size (submerged area; m2) increased downstream. In upstream reaches smaller logjams formed on fallen trees or gravel bars in higher velocity channel units (i.e., riffles, runs), and larger logjams downstream formed on fallen trees or meanders in pools. We found no evidence of snorkeling observer bias, and juvenile salmon were present at 68% of logjams and their density (fish/ m2) ranged from 0.0002 to 9.0000. The highest densities occurred in the middle reaches of the network and corresponded with high quality adult spawning habitats. Our current work focuses on modeling juvenile salmon density as a function of logjam characteristics and unbiased population estimates using a spatial-stream-network model. Results of this project will be used to evaluate the potential for reintroduction of LWD to reaches of the Chena River below Moose Creek Dam, provide juvenile salmon rearing capacity estimates for the basin, and contribute towards efforts to monitor LWD based on remote sensing and link the distribution and abundance of wood along the river to wildfire and land management practices. Co-Investigators: Jimmy Fox (USFWS) Bob Henszey (USFWS) Katherine Lininger (CU-Boulder) Tanana Valley Watershed Association Collaborators: University of Alaska Fairbanks, USGS, Alaska Department of Fish and Game, U.S. Fish and Wildlife Service |
Outreach:
TVWA Fish Forts (September 18 2018) YouTube Chena logjams could be key to salmon survival (October 10 2017) UAF News and Information Products: Oral and poster presentations: Falke, J.A., Cathcart, C.N., Fox, J., Henzsey, R., and K. Lininger. 2019. Longitudinal patterns of logjams and occupancy by juvenile Chinook Salmon along a sub-Arctic boreal riverscape. American Fisheries Society Annual Meeting, Reno, Nevada, 29 September – 3 October, 2019. Cathcart, C.N., Falke, J.A., Crabill, B., and J. Fox. 2018. Longitudinal patterns of logjams and occupancy by juvenile Chinook Salmon in the Chena River, Alaska. Western Division American Fisheries Society Annual Meeting, Anchorage, Alaska, 21-25 May, 2018. |