Monitoring Federally Listed Bull Trout (Salvelinus confluentus) Movements Proximate to Bureau of Reclamation Dams in the Yakima Basin

It is well known that bull trout (Salvelinus confluentus) in western river basins have been negatively impacted by the obstruction of free-flowing rivers and by altered hydrology. The effects include loss of habitat, population fragmentation and genetic isolation. The subsequent decline in bull trout abundance due to these and other factors prompted the U.S. Fish & Wildlife Service (USFWS) to list bull trout as a threatened species in 1998 under the Endangered Species Act (ESA) (USFWS 1998). In the Yakima basin, the Washington Department of Fish & Wildlife (WDFW) has been monitoring bull trout populations since the mid 1980’s. The primary focus has been to identify spawning areas and to monitor abundance through annual redd count surveys. In the last several years there has been increased use of radio telemetry techniques to determine movement patterns (migration timing), wintering areas and habitat preferences of bull trout populations. Although this technique has been used for monitoring fluvial bull trout in the Yakima Basin, (Mizell et al. 2008) less was known about adfluvial bull trout movement patterns in the basin reservoirs. The primary purpose of this study was to use radio-telemetry as a tool to obtain information on adfluvial bull trout movements proximate to U.S. Bureau of Reclamation (Reclamation) dams and to determine effects of these structures and operations on bull trout populations. We also collected tissues from bull trout captured on this project to determine the genetic relationships between fluvial and adfluvial fish in the Yakima basin. Additional funds were recently secured thru the USFWS to complete the genetic analysis and to compare the results with samples collected from other populations in the Yakima basin (see Hawkins and Von Bargen 2006). A final genetics report is expected in March 2009. Together, the radio telemetry and genetics information may be useful to Reclamation managers for making decisions about altering their structures and operations to reduce negative impacts on bull trout.

During this study, five adult bull trout were captured and radio-tagged in the N.F. Tieton River between Clear Lake and Rimrock Reservoir, seventeen were captured and tagged in Deep Creek (tributary to Bumping Reservoir) and twelve adult bull trout were captured and tagged from the large pool in the Tieton River below the Tieton (Rimrock Reservoir) dam during a fish salvage operation prior to the installation of hydropower turbines at the dam. All thirty-seven of the salvaged bull trout, including the twelve radio-tagged fish, were transported approximately 22 river miles downstream and released into the large pool below the Wapatox Irrigation Diversion Dam on the main stem Naches River. Of the 17 radio-tagged fish in Deep Creek (Bumping Reservoir system), seven were tagged with archival tags to automatically record depth and temperature. All radio and archival tags were surgically implanted in the body cavity of the fish. We believe that surgical implantation of the Lotek archival (temperature/depth) tags had not been attempted before. Previous studies anchored the tags on the dorsal surface of the fish, but most tags were lost with this external attachment (Kelly Ringel & DeLaVergne 2005). Four of our seven archival-tagged fish also shed their tags and/or died due to predation or complications inherent to surgical implantation of the tags before migrating out of Deep Creek, but three survived and were radio-tracked back to the reservoir. The archival tags of two of these fish were retrieved on the spawning grounds a year later when they returned to spawn. Weekly radio tracks of all tagged fish were conducted using both fixed station and mobile Lotek receiverâ€"antennae tracking units.

None of the radio-tagged bull trout moved out of Bumping Reservoir past the dam either thru the outlet works (sluiceway) or the overflow (spillway) channel. None of the large Yakima basin reservoir dams are conducive to safe and efficient fish passage downstream and none have fish ladders for upstream fish passage. In Bumping Reservoir, tagged fish usually stayed in the upper (deep) section of the lake during the winter, but became much more active in the spring and summer, occasionally coming in close proximity to the dam. As expected, we detected fish moving towards Deep Creek prior to the spawning period and we tracked fish back up into the spawning area a full year after they were tagged.

Similarly, none of the five radio tagged bull trout in the N. Fork Tieton moved up past the fish ladder at Clear Lake Dam (upstream of Rimrock Reservoir). Instead, within a few months of tagging, these fish moved downstream to Rimrock Reservoir where they over wintered. Some did come in close proximity to the outlet structure at Tieton Dam, but none of our adfluvial tagged fish were tracked below it. However, we did loose the signal for one fish near the dam. It is unknown what became of this fish/tag. The other four-tagged fish moved to the upper end of the reservoir (near the N.F. Tieton River) in May-June. One of these fish moved to the base of Clear Lake Dam by late June and another was tracked to the spawning grounds in Indian Creek (tributary to N. Fork) in September; a little over one year after bring tagged in the N. Fork. Indian Creek is one of two major spawning areas for bull trout inhabiting Rimrock Reservoir, the other being the S. Fork Tieton River. We did not track any tagged bull trout into the S. Fork, which lies near the opposite end of the lake from the N. Fork. Later in the fall, the remaining tagged fish moved back to the mid section of Rimrock Reservoir where they over wintered.

Radio tagged bull trout that were salvaged from the Tieton River below Tieton Dam (Rimrock Reservoir) were trucked downstream and released into the Naches River below the confluence of the Tieton River. Only one of these fish ventured back up into the Tieton River, but eventually it moved back to the Naches River where it, along with others migrated upstream to spawning areas in the American River and Rattlesnake Creek. Essentially, these transplanted fish integrated themselves with existing fluvial populations in the Naches River. However, it appears that unless these fish are transported out of the area and placed with other bull trout populations they do not make the journey on their own. During an earlier bull trout tagging operation (Mizell et al. 2008) bull trout were tagged and immediately released below the dam. These fish did not leave the area, but instead they stayed in or near the large pool below Tieton Dam.