Pacific lamprey (Entosphenus tridentatus) populations throughout the Columbia River Basin (CRB) are in decline.  Multiple reasons for the decline have been identified including passage at mainstem CRB dams and habitat degradation; however, little is known about limiting factors within CRB tributaries.  Declining lamprey populations is of primary concern to the Confederated Tribes of the Warm Springs Reservation of Oregon (CTWSRO) due to their significant cultural and ecological value.  Accordingly, the project intent is to expand knowledge of lamprey populations and factors limiting production in the Deschutes and Hood rivers as well as Fifteenmile Creek subbasins.  This information will be used to inform management and restoration actions for establishment, conservation and/or maintenance of harvestable populations for perpetuity.

Prior to the project 2002-016-00, little was known about Pacific lamprey in the Deschutes River Subbasin.  To date knowledge of Pacific lamprey in lower Deschutes River Subbasin has been greatly expanded including over-winter, spawning and rearing habitats, upper extent of distribution, larval densities were related to habitat variables, escapement and harvest estimates were estimated at Sherars Falls from 2004 through 2014, migration patterns were documented through radio-telemetry and PIT tag arrays, and genetic identification has been confirmed.  From this information, potential limiting factors are being examined.

Seufert Falls (rkm 0.4) on Fifteenmile Creek is an important Pacific lamprey harvest location for CTWSRO tribal members.  Since 2011, escapement and harvest estimates have been made for Pacific lamprey, as well as migration patterns of PIT tagged lamprey at several locations in the subbasin.  Larval densities and distribution have been documented in Fifteenmile and nearby Mill creek subbasins.  In Fifteenmile Creek Subbasin, the greatest threat to lamprey has been summertime stream conditions with low water and high temperatures, as water is withdrawn for agriculture, past chemical spills that have been shown to remain in tissue samples, and passage barriers, although ODFW restored passage at the lowermost diversion dam.  Work will continue to improve stream conditions by partnering with the local irrigation district, watershed council, and ODFW.

The CTWSR documented re-establishment of Pacific lamprey upstream of the Powerdale Dam site since its removal in fall 2011.  Lamprey were once widely distributed throughout the Hood River basin (USFS 1996); however, lack of adequate passage facilities at Powerdale Dam (rkm 7.2) is believed to have eradicated lamprey from areas upstream.  Since 2012, Pacific lamprey have increased distribution in Hood River and East Fork Hood River 15km since dam removal.  We will continue to monitor lamprey re-colonization in Hood River and document migration patterns through PIT tag arrays.

This project (2011-014-00) combines former projects 2002-016-00 and 2007-007-00.  Project objectives are consistent with those identified by the Columbia Basin Pacific Lamprey Technical Work Group (CBPLTWG).