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The Problem Recovery of threatened and endangered salmonid populations is a high regional and national priority. Threatened and endangered salmonids in the Pacific Northwest often use backwaters and wetlands as they migrate toward the ocean, however our understanding of the role of wetlands to juvenile salmonids is limited. Wetlands may provide highly productive sites for salmonids that use off-stream habitat for rearing or holding during downstream migration. Wetlands may improve water quality, function for water storage, and lessen the impacts of severe flooding. On the other hand, wetlands managed in the absence of information on salmonid life history and habitat needs may trap juvenile salmonids,
Toppenish Creek, in south-central Washington State, contains a run of Mid-Columbia River steelhead, a federally listed threatened species. Managers of the Toppenish National Wildlife Refuge (NWR; U.S. Fish and Wildlife Service) are required to consult with the National Marine Fisheries Service on the potential impact of refuge operation on threatened steelhead. Managers of the refuge need information to help them prepare this consultation, and to better manage habitat that influences this threatened species. Toppenish NWR covers 1,978 acres of floodplain along Toppenish Creek, a tributary of the Washington's lower Yakima River. Toppenish Creek flows west to east from the east slope of the Cascade Mountains through the arid shrub-steppe ecosystem and into the intensive agricultural area in the lowlands of the Yakima valley. Toppenish NWR is located approximately 15 km. from the confluence of Toppenish Creek and the Yakima River. Objectives In 2001, USGS started a study at Toppenish NWR to provide the refuge managers with better information about wetland effects on juvenile steelhead. The major Objective of the study was to determine whether juvenile steelhead were being tapped on the wetland during spring, and whether this was detrimental or beneficial to the fish. Results may lead to changes in water management practices (flooding times, drawdown of specific units, etc.), changes in mowing practices, or physical changes in wetland structure. Methodology
Monitoring of fishes on Toppenish NWR was conducted during late winter and spring when downstream juvenile migration is occurring and wetland units are flooded. Fyke-net-type traps were set at entrance and exit points to wetland units. Fish captured in the traps were weighed, measured and tagged with Passive Integrated Transponder (PIT) tags. PIT tags allow identification of individual fish. In some units, we tagged fish entering a wetland unit and re-capture fish at the lower end of the unit when they exit. These re-captured fish provide information on growth, survival, and residence time in the wetland unit. PIT tags also allow for the possibility of detection at downstream interrogation sites such as Prosser Dam on the Yakima River, the mainstem Columbia River Dams, and through trawls in the Columbia River Estuary. Basic water quality parameters, especially temperature, were monitored in the wetland units and in Toppenish Creek. Water temperatures were monitored with four thermographs distributed throughout the refuge. Researchers are collaborating with others working in the area, such as the Yakama Indian Nation. Highlights and Key Findings Sampling at Toppenish National Wildlife Refuge in 2001 documented the occurrence of 12 species of fish (1,514 individuals). Juvenile steelhead were captured at both the upper Snake Creek trap (N = 159) and the lower Snake Creek trap (N = 81). We estimated the travel time (days) of steelhead through one of the wetland units and documented the sizes, condition, and seasonal occurrence of fish. Water temperature varied considerably around the refuge and increased to near-lethal levels by June. These results were summarized in a report provided to the USFWS (I. Jezorek and J. Petersen. 2002. Monitoring and assessment of juvenile steelhead on Toppenish National Wildlife Refuge. 39 p.). This study continued through 2002, but data have not been analyzed. Where Are We Headed In 2003 Sampling of steelhead will continue during the spring of 2003, and a final report will be prepared. Information will be provided to the U.S. Fish and Wildlife Service and regional groups through meetings and reports. Project Contact Alec Maule Email: alec_maule@usgs.gov Publications |
