Lake Roosevelt Fisheries Evaluation Program, Part A; Fisheries Creel Survey and Population Status Analysis, 1998 Annual Report.

The Lake Roosevelt Fisheries Evaluation Program is the result of a merger between two projects, the Lake Roosevelt Monitoring Program (BPA No. 8806300) and the Lake Roosevelt Data Collection Project (BPA No. 9404300). These projects were merged in 1996 to continue work historically completed under the separate projects, and is now referred to as the Lake Roosevelt Fisheries Evaluation Program. Creel and angler surveys estimated that anglers made 196,775 trips to Lake Roosevelt during 1998, with an economic value of $8.0 million dollars, based on the Consumer Price Index (CPI). In 1998 it was estimated that 9,980 kokanee salmon, 226,809 rainbow trout, 119,346 walleye, and over 14,000 smallmouth bass and other species were harvested. Creel data indicates that hatchery reared rainbow trout contribute substantially to the Lake Roosevelt fishery. The contribution of kokanee salmon to the creel has not met the expectations of fishery managers to date, and is limited by entrainment from the reservoir, predation, and possible fish culture obstacles. The 1998 Lake Roosevelt Fisheries Creel and Population Analysis Annual Report includes analyses of the relative abundance of fish species, and reservoir habitat relationships (1990-1998). Fisheries surveys (1990-1998) indicate that walleye and burbot populations appear to be increasing, while yellow perch, a preferred walleye prey species, and other prey species are decreasing in abundance. The long term decreasing abundance of yellow perch and other prey species are suspected to be the result of the lack of suitable multiple reservoir elevation spawning and rearing refugia for spring spawning reservoir prey species, resulting from seasonal spring-early summer reservoir elevation manipulations, and walleye predation. Reservoir water management is both directly, and indirectly influencing the success of mitigation hatchery production of kokanee salmon and rainbow trout. Tag return data suggested excessive entrainment occurred in 1997, with 97 percent of tag recoveries from rainbow trout coming from below Grand Coulee Dam. High water years appear to have substantial entrainment impacts on salmonids. The 1998 salmonid harvest has improved from the previous two years, due to the relatively water friendly year of 1998, from the harvest observed in the 1996-1997 high water years, which were particularly detrimental to the reservoir salmonid fisheries. Impacts from those water years are still evident in the reservoir fish populations. Analysis of historical relative species abundance, tagging data and hydroacoustical studies, indicate that hydro-operations have a substantial influence on the annual standing crop of reservoir salmonid populations due to entrainment losses, and limited prey species recruitment, due to reservoir elevation level fluctuation, and corresponding reproductive success