Contract Description:
The rise of Rufus Woods Lake as a regionally popular area for catching large (>500 mm) Rainbow Trout Oncorhynchus mykiss coincided closely with the establishment of net pen aquaculture in 1989 (Shallenberger 2010). Throughout the history of net pen aquaculture management on Rufus Woods Lake, there has been a range in Rainbow Trout escapement numbers. Escapements of large Rainbow Trout from net pen facilities resulted in increased fishing opportunities for boat and shore anglers (Shallenberger 2010). The CCT further recognized the potential use of net pen facilities to increase Rainbow Trout fishing opportunities in Rufus Woods Lake. In coordination with Columbia River Fish Farms (a private net pen operator), the CCT also funded Rainbow Trout augmentation from 1997 to 2005 and released more than 200,000 fish. Opportunities for anglers to catch large Rainbow Trout increased angler usage throughout this period, and Rufus Woods Lake quickly became a popular fishing destination (Shallenberger 2010). In 2002, the Washington State record Rainbow Trout was caught in Rufus Woods Lake (13.4 kg).
Previous years' creel data suggested the highest catch and catch rates of large Rainbow Trout from Rufus Woods Lake were maintained at high levels due to net pen fish escapements and not from CCT fish stocking efforts (Shallenberger 2010; Keleher and Cross 2015a). Specifically, from 2006 to 2008, total fish escapement estimates ranged between 300,000 and 400,000 fish, which resulted in more than 40,000 angler days spent on Rufus Woods Lake annually and made it the most popular fishing destination on the CCT Reservation (Shallenberger 2009). Stocking by CCT accounted for a large portion of harvested Rainbow Trout from 2007 to 2010, during periods when net pen escapement was low, with the majority of stocked catchable size Rainbow Trout contributing to the fishery during the first months after their release (Shallenberger 2009 and 2010; Keleher and Cross 2015a). In June and July of 2011 throughout the reservoir, angler effort reached 55,009 and 90,223 angler hours with Rainbow Trout catches of 32,356 and 39,384, respectively (Keleher and Cross 2015a). High river flow conditions and spill at Grand Coulee Dam during spring runoff in 2011 led to prolonged exposure to elevated total dissolved gas levels (>120% for 40 consecutive days). The combination of high total dissolved gas levels and river flow conditions caused fish mortalities to weigh down and tear net pens, creating a mass escapement of Rainbow Trout into Rufus Woods Lake. The accidental escapement led to the large increase in angling effort and catch observed in Rufus Woods Lake in June and July of 2011 (Keleher and Cross 2015a).
Annually maintaining a Rainbow Trout fishery in Rufus Woods Lake similar to that experienced during periods with high net pen escapement would require resources beyond those of the CCT Fish and Wildlife Department. However, CCT fisheries managers have set similarly high goals for this fishery (CCTFW 2015). Rearing or purchasing large Rainbow Trout for release into the reservoir in numbers similar to those that previously escaped has proven cost prohibitive. To achieve a fishery similar to one maintained by high net pen escapement, tens-of-thousands of Rainbow Trout greater than 500 mm in total length would need to be stocked or smaller (e.g., ~250 mm) stocked Rainbow Trout would need to grow beyond 500 mm. From 2009 to 2013, several thousand Rainbow Trout that averaged 1,660 g/fish (3.69 lb/fish) were purchased directly from local aquaculture facilities by CCT and stocked into Rufus Woods Lake, but this stocking did not mimic numbers seen during previous escapements. Additionally, previous studies have shown little potential for the success of a put-grow-and-take fishery in Rufus Woods Lake due to a perceived underutilization of the prey-base by released fish (e.g., relatively high proportion of empty stomachs observed in released fish while ample prey resources appeared to be available in the reservoir; Richards et al. 2011; Rensel et al. 2013). Thus, realistic and achievable management objectives and actions that account for a balance between the numbers and size of fish released needed to be determined.
In 2015, management objectives for Rufus Woods Lake were created and management actions to achieve these objectives were recommended based on the information available at the time. These objectives and metrics were set forth in the Colville Tribes Fisheries Management Plan for Stocked Waterbodies (CCTFW 2015). This document was then updated in 2020 (CCTFW 2020). Specific fishery objectives are to maintain a total annual angler harvest of 40,000 Rainbow Trout with more than 49% of these fish measuring over 400 mm and 5% measuring over 500 mm. The suggested management actions implemented to achieve the fishery objectives included annually stocking 50,000–75,000 Rainbow Trout averaging = 400 g/fish during the spring prior to spill at downstream Chief Joseph Dam (CCTFW 2020). This creel survey is used to evaluate if these objectives are being met and to help guide fish stocking efforts. Specifically, the creel survey seeks to estimate:
1. Shore, boat, and total angler effort (angler-hours).
2. Average catch and harvest rate (number of fish per angler-hour) for all Rainbow Trout and individual sources of Rainbow Trout (when possible).
3. Total catch and harvest for all Rainbow Trout and individual sources of Rainbow Trout (when possible).
4. Harvested fish size statistics (length) for all Rainbow Trout and individual sources of Rainbow Trout (when possible).
Finally, native Redband Trout are a conservation priority for the CCT, and the level of entrainment into Rufus Woods Lake and utilization of Nespelem River habitat will be documented to inform conservation efforts. As such, a PIT tag array (installed in 2018) and will be used to help quantify the number of Redband Trout entraining into Rufus Woods Lake from Lake Roosevelt (e.g., Sanpoil River origin) and utilizing habitat available in the Nespelem River. This information will be used to assess relative changes in Redband Trout abundance as a result of possible future management actions, including interactions with released triploid Rainbow Trout.