Stehekin River Mainstem Westslope Cutthroat and Rainbow Trout Surveys, NPS. Despite the apparent lack of spawning WCT in Stehekin River tributary and side channel index sites, a number of large (380-460 mm) WCT were viewed in the mainstem Stehekin River during the autumn 2010 kokanee surveys. Though not observed while spawning, these observations confirm the presence of large, potentially adfluvial WCT in the Stehekin River system. In light of these observations in 2011 it was decided to refocus our efforts to include distribution and abundance surveys of trout during the late summer and early fall during low flow periods. The objectives of these surveys were to gain a better understanding of adfluvial WCT abundance and distribution in the Stehekin River system and to assess management activities designed to increase the WCT population and reduce the population of non-native XXX. Eight large channel spanning pools were initially identified in the lower 7 km of the mainstem Stehekin River which were surveyed once in the early spring, and twice in the late summer/ early fall of 2011. Six of the eight pools located in 2011 were selected for continued surveys from 2012 to 2014. Pool selection was based on documented WCT presence and safety of conducting snorkel surveys under elevated flow conditions. Survey methods and pool location maps were included in the 2009-2011 spawning survey report (Xxxxxxx and Xxxxxx 2012) while a comprehensive report covering 2011-2014 mainstem pool results will be completed in the spring of 2015. Snorkel surveys were conducted by teams of two, with one surveyor counting fish and one surveyor on the channel bank timing the snorkel pass and recording data. Fish were tallied into length groups of less than 150 mm, 150–299 mm, 300–449 mm, and ≥450 mm. Each pool was snorkeled three times and the number of fish observed by species and observation time was recorded for each pass. Results are outlined in Table 13 below. Table 13: Number of greater than six inch trout observed and size classes within six mainstem pool index sites, 2011 – 2013. Number of fish observed Westslope Cutthroat Trout Rainbow Trout Eastern Xxxxx Xxxxx Survey Date 150-299 mm 300-449 mm ≥450 mm 150-299 mm 300-449 mm ≥450 mm 150-299 mm 300-449 mm ≥450 mm 8/2/2011 3 1 0 10 3 0 0 0 0 8/30/2011 0 2 0 11 4 0 0 0 0 8/15/2013 N/A1 N/A1 N/A1 N/A1 N/A1 N/A1 N/A1 N/A1 N/A1 9/18/2013 N/A1 N/A1 N/A1 N/A1 N/A1 N/A1 N/A1 N/A1 N/A1 1 - Due to intense rainfall and high river turbidity surveys were not completed on these dates. In 2012 and 2013, North Cascade...
Stehekin River Mainstem Westslope Cutthroat and Rainbow Trout Surveys, NPS. Surveys were conducted from 2012 to 2014 in the mainstem of the Stehekin River to assess management activities designed to increase the WCT population and reduce the population of non-native XXX. These surveys were discontinued after 2014, and below is a summary of results that have been reported in more detail in previous annual reports. Pilot work conducted in 2011 identified eight channel-spanning pools in the lower 7 km of the Stehekin River and six of these pools were selected for continued surveys that were conducted from 2012 to 2014. These pools were selected based on the safety of conducting snorkel surveys under anticipated flow conditions. Snorkel surveys were conducted by teams of two, with one surveyor counting fish and one surveyor on the channel bank timing the snorkel pass and recording data. Fish were tallied into length groups of less than 150 mm, 150–299 mm, 300–449 mm, and ≥450 mm. Each pool was snorkeled three times and the number of fish observed by species and pass duration was recorded. Of the three snorkel passes, the maximum fish count for each species was compared by the date the survey was conducted (Figure 4).
