Evaluating Re-colonization of the White Salmon River by Anadromous Salmonids

Under this project, the PCSRF funds specifically were used to conduct adult spawner surveys, redd count surveys and carcass surveys on 7.6 miles of stream but another 25.4 miles of stream were monitored using other funding sources resulting in a total of 33 miles monitored. The data collected documents the recolonization, spatial distribution, and relative abundance of anadromous salmonids in the White Salmon River subbasin following the removal of Condit Dam. In the 2016 surveys, a total of 10 possible redds, 11 probable redds, and 2 definite redds were observed. Wading surveys were conducted within the known or likely geographic range for steelhead in White Salmon tributary streams, starting where possible above or near complete or partial passage barriers and moving downstream. Access due to land ownership limited survey coverage in some areas. The White Salmon River mainstem was not surveyed due to generally high flows and limited visibility. Individual redds were counted and their locations recorded using handheld GPS units.

These surveys represent the first known documentation of steelhead spawners returning to White Salmon River tributaries; adult steelhead had been observed and documented in the mainstem White Salmon River beginning in summer 2012 (the first full year following the breaching of Condit Dam in October 2011). Results indicate that steelhead spawners are now recolonizing most accessible streams in the subbasin. These results suggest a moderately low level of recolonization by adult steelhead in these streams to date, with some evidence of increasing numbers of redds since dam removal (Figure 2). Possible origins of these fish include stray steelhead from other river basins, large migratory rainbow trout from the White Salmon River or Columbia River, or returning steelhead from previously resident rainbow trout populations in these tributary streams. While steelhead redd counts often do not yield robust spawner abundance estimates, applying a commonly-used fish-per-redd estimate of 2.5 (Gallagher et al. 2007) to all observed redds in 2015 and 2016 yields spawner abundance estimates of approximately 55-58 fish in the surveyed reaches of White Salmon River tributaries. Results from these surveys likely represent a minimum spawner abundance level, due to some temporal and visibility limitations (i.e., earlier-returning steelhead spawners may have gone undetected in these surveys).

After a century of blocking anadromous fish passage on the White Salmon River, Condit Dam has now been removed. Initial dam breach occurred on October 26, 2011 and all remaining dam structures were removed by October 2012. Monitoring of recolonization by anadromous adult salmonids by various agencies is only being accomplished in a minimal and piecemeal fashion, with funding unavailable for broad-scale comprehensive monitoring projects. This project will document adult spawner escapement and spatial distribution for Middle Columbia River steelhead (listed as ESA threatened) in several key tributaries to the White Salmon River (which constitute likely spawning and rearing streams). Other species (coho, spring and fall Chinook) may be monitored in cooperation with other agencies as time and funding allows.

Results of the Project: Survey/stream reach mileage increased each year during 2012 to 2014 as additional access permission was sought and granted. Surveys in 2012 covered the lowermost 3.0 miles of Rattlesnake Creek (including habitat above a possible partial barrier falls at RM 1.6) and the lowermost 0.1 miles of Indian Creek. Surveys in 2013 covered the same reaches of Rattlesnake and Indian creeks as well as the lowermost 3.9 miles of Buck Creek (including habitat above a possible partial barrier falls at RM 3.6). Surveys in 2014 covered the same reaches as 2013 as well as the lowermost 0.3 miles of Mill Creek (below a partial barrier culvert) and the lowermost 0.6 miles of Spring Creek (below a barrier small dam). Surveys in 2015 and 2016 covered the same reaches as 2014. Figure 1 shows a map of observed redds.

No redds, live fish, or carcasses were observed in the 2012 surveys. In the 2013 surveys, a total of 7 possible redds and 4 probable redds were observed. Two possible redds and 3 probable redds were recorded on Rattlesnake Creek; five possible redds and 1 probable redd were recorded in Buck Creek; and no redds were observed in Indian Creek. In addition, one live steelhead (in Buck Creek) and two steelhead carcasses (one each in Rattlesnake and Buck creeks) were observed. Of the carcasses observed, one had an intact adipose fin and one was too decomposed to determine adipose fin presence. Genetic samples were collected from carcasses but all tissue samples were unfortunately too degraded for genetic analysis.

In the 2016 surveys, a total of 10 possible redds, 11 probable redds, and 2 definite redds were observed. Four possible redds and 3 probable redds were recorded on Rattlesnake Creek; 4 possible redds, 5 probable redds, and 1 definite redd were observed in Buck Creek; 1 possible redd and 1 probable redd were observed in Spring Creek; 1 possible redd, 2 probable redds, and 1 definite redd were observed in Mill Creek; and no redds were observed in Indian Creek. Three live adult steelhead were observed; 1 in Rattlesnake Creek, 1 in Buck Creek, and 1 in Mill Creek. The live steelhead in Rattlesnake Creek was observed near the upstream end of the survey area, at approximately RM 2.6, well upstream of the RM 1.6 falls.