Lake Roosevelt Fisheries Evaluation Program Limnological and Fisheries Monitoring Annual Report 1999 August 1999 DOE/BP-32148-8 This Document should be cited as follows: McLellan, Holly, Chuck Lee, Ben Scofield, Deanne Pavlik, "Lake Roosevelt Fisheries Evaluation Program; Limnological and Fisheries Monitoring", 1999 Annual Report, Project No. 199404300, 226 electronic pages, (BPA Report DOE/BP-32148-8) Bonneville Power Administration P.O. Box 3621 Portland, OR 97208 This report was funded by the Bonneville Power Administration (BPA), U.S. Department of Energy, as part of BPA's program to protect, mitigate, and enhance fish and wildlife affected by the development and operation of hydroelectric facilities on the Columbia River and its tributaries. The views in this report are the author's and do not necessarily represent the views of BPA. Lake Roosevelt Fisheries Evaluation Program Limnological and Fisheries Monitoring Annual Report January 1999 – December 1999 Prepared by: Holly McLellan Chuck Lee Ben Scofield and Deanne Pavlik Spokane Tribe of Indians Department of Natural Resources Wellpinit, WA 99040 Prepared for: U.S. Department of Energy Bonneville Power Administration Division of Fish and Wildlife Portland, OR 97208-3621 Project No. 1994-043-00 Contract No. 94BI32148 March 2003 Executive Summary Lake Roosevelt is a large reservoir (243 km long with 334.9 km2 surface area) on the upper Columbia River. Grand Coulee Dam holds Lake Roosevelt and is operated for multiple uses including power production, flood control, irrigation, and recreation. There is a mitigation and sport fishery in Lake Roosevelt important to the region. Monitoring of the fishery and ecosystem within the reservoir were conducted in 1999 to assist in balancing the management of the reservoir for multiple uses. Precipitation accumulation was 107 % of normal in the basin above Grand Coulee Dam. This resulted in outflows at Grand Coulee Dam that were 23 % above the 15 year average (1983-1998). The annual (1999) inflow, outflow, and water retention time in Lake Roosevelt were 130.7 kcfs, 127.4 kcfs and 32.1 days respectively. The higher river flows contributed to an annual mean total dissolved gas saturation of 110 %. Total dissolved gas surpassed the 110 % standard established by Washington state, 51 % of the year at the monitoring station near the U.S./Canadian border, and 37 % of the year at Grand Coulee Dam forebay. - Most of the dissolved nitrogen in Lake Roosevelt was present in the NO3 form where the annual average was 0.119 mg/L across all locations. Phosphorus in Lake Roosevelt was relatively scarce with an annual average total phosphorus (TP) concentration of 0.006 mg/L across all locations. Annual average total nitrogen and TP ratios (36:1) reflect the limiting nature of phosphorus in Lake Roosevelt. Carlson’s trophic state index places Lake Roosevelt in the meso-oligotrophic range (overall annual mean TSI=34). Mean phytoplankton chlorophyll a concentrations over the entire year were low at 1.9 mg/m3. Annual phytoplankton densities and biovolumes averaged 147 organisms/ml and 0.046 mm3/L respectively. Phytoplankton density and biovolume peaked in the summer. Phytoplankton average density and biovolume was significantly greater at Porcupine Bay than most other sampling locations. Inflow to Lake Roosevelt was positively correlated with phytoplankton density. This was in part, driven by increased nutrients available to phytoplankton for assimilation. Since phosphorus is limiting, increasing inflow brings particulates with adhering phosphorus that supply phytoplankton growth. Total phosphorus was negatively correlated with water 2 retention time, which also supports this assertion. Reduced inflow can lessen phosphorus available to phytoplankton reducing total primary production available to higher trophic levels alternately; holding the water in Lake Roosevelt can reduce entrainment of zooplankton and fish. Further, investigation is needed to balance the benefits of flow yet reduce the entrainment of sport fish. Littoral production is limited by changing reservoir elevation. Although limited by the hydraulics of the reservoir, the littoral zone has shown increased productivity. The trophic state index (TSI) that uses phytoplankton chlorophyll a, Secchi disk depth, and total phosphorus values to estimate trophic status was used to compare littoral and pelagic zones. Littoral TSI values (37) were significantly higher than pelagic TSI values (33) during 1999. Increased TSI values at littoral sites was due to reduced Secchi depths and no TP determination in the littoral. Additionally, zooplankton showed significantly greater densities and biomass at the shore sampling sites when compared with pelagic sites. There were 16 species of zooplankton observed in Lake Roosevelt. Copepods were most abundant, accounting for 80.5 % (annual mean 1,111.2 organisms/m3) of total pelagic zooplankton density. Daphnia and other Cladocera contributed 17.4 % (annual mean 280.8 organisms/m3) and 2.0 % (annual mean 21.7 organisms/m3) of overall zooplankton density respectively. Mean overall zooplankton densities were lowest in the winter and highest in summer and fall, values ranged from 43.5 organisms/m3 (January) to 961.5 organisms/m3 (September). Mean total pelagic zooplankton densities were lowest in the upper reach (Evan’s Landing 42.1 organisms/m3) and highest in the lower reach (Sanpoil River Confluence 897.7 organisms/m3) of the reservoir. Zooplankton lengths ranged from 0.4 to 10.4 mm in Lake Roosevelt. Daphnia exhibited the greatest annual mean lengths (1.18 mm), followed by other Cladocera (0.55 mm), and Copepoda (0.43 mm). Annual mean lengths were greatest in the middle and lower reaches (Spokane River Confluence 0.65 mm) and smallest in the upper reach (Evan’s Landing 0.34 mm) of the reservoir. Zooplankton biomass was dominated by Daphnia at 62.5 % (annual mean biomass 3,579.2 µg/m3) of the total pelagic biomass. Copepoda contributed 35.8 % of the total pelagic 3 zooplankton biomass (annual mean biomass 1,757.4 µg/m3). Other Cladocera accounted for the remaining 1.7 % of the total pelagic zooplankton biomass (annual mean biomass 64.8 µg/m3). Similar to zooplankton densities, mean total biomass was lowest in the winter/spring and highest in September (3,377.3 µg/m3). Mean total pelagic biomass was greatest in the lower reach (1,924.0 µg/m3) and lowest in the upper reach (47.4 µg/m3) of the reservoir. There was a strong (r2=0.948) direct relationship observed between temperature and total pelagic mean zooplankton biomass. Fisheries surveys indicated a reduction in catch-per-unit-effort of all fish species except brown trout in 1999 compared to 1998. The two most abundant fish species, large scale suckers and walleye exhibited the greatest reductions. The CPUE decreased for largescale suckers from 44.59 to 6.22 fish/hr and walleye decreased from 55.01 to 6.68 fish/hr. Hatchery rainbow trout growth was slightly lower in 1999 than in previous years, but still higher compared to local lakes. Hatchery kokanee growth was stable when compared to previous years in Lake Roosevelt. Walleye growth was also stable compared with previous years, and was similar to growth observed in other local lakes and reservoirs with walleye present. Walleye fed primarily on Cottidae (16.56%) and Salmonidae (17.94 %) families. Walleye diet was more diverse in previous years. High diet overlap occurred between pelagic fish species, which fed primarily on zooplankton. These instances of high diet overlap may result in interspecific competition when zooplankton densities are compromised by reservoir operations. High diet overlap also occurred between piscivorous fish. Competition likely resulted from low densities of small prey fish available in the reservoir. Tagging studies from 1999 were similar to results from previous years, in that high water years increase the number of tags collected below Grand Coulee Dam, while low waters years decrease entrainment. Phalon Lake rainbow trout marked and released in the Kettle Falls area were only recaptured in the northern section of the reservoir, suggesting that this locally adapted stock tends to stay in local areas without migrating downstream like the coastal stock rainbow trout tend to do. 4 Analysis of the creel survey data indicated that the Lake Roosevelt fishery brought in $6.12 million to the local economy in 1999. An estimated 230,513 angling trips were made to Lake Roosevelt, in 1999, the highest use observed for the reservoir since 1995. Kokanee harvest was down from the previous year (n=1,730), however half of the fish were estimated to be of hatchery origin. Rainbow trout harvest estimates were similar to the previous year (232,019). Fish of hatchery origin dominated in both the kokanee and rainbow trout harvest. Estimated walleye harvest in 1999 was greater than estimated harvest in 1998 (n=236,738). Closure of the Spokane Arm to fishing during the walleye spawning season, ultimately protects them from over harvest during a very sensitive time in their life history, during which they congregate in large numbers. Lake Roosevelt is a dynamic system altered with large drawdowns, limited habitat, and abundant non-native fish species. The reservoir fishery is an important economic stimulus for regional businesses and deserves the utmost attention. 5 Acknowledgments We gratefully acknowledge Dr. Allan Scholz (Eastern Washington University), and Casey Baldwin (Washington Department of Fish and Wildlife, WDFW) for advice and scientific input on this project. We thank William Matt Sr., Hank Etue, Randy Peone, Andy Moss, Joni Wynecoop, (Spokane Tribe of Indians, STI), Jim Meskan (WDFW), and Leroy Williams (Colville Confederated Tribes, CCT), for collection of creel and fisheries population data, and assistance with other fisheries management, and fish culture monitoring operations. Much appreciation goes to Jason McLellan (WDFW) and Heather Woller (WDFW) for their assistance in the editing process. We also thank Rudy Peone, Tim Peone, and Mary Verner (STI), John Whalen and Mitch Combs (WDFW), Jerry Marco, Monty Miller, and Richard LeCaire (CCT), for counsel, advise and support in all areas.