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Staff Accomplishments

PNNL research helps protect dwindling Pacific lamprey

June 2005
Pacific lamprey may not be the handsomest fish in the sea but they are dwindling in numbers and that decline has prompted the U.S. Army Corps of Engineers to enlist Pacific Northwest National Laboratory in efforts to protect the native Northwest species. Studies by PNNL have changed Corps policy to make dam passage safer for the migratory juvenile lamprey, who like salmon must traverse up to eight dams on the Snake and Columbia rivers enroute from upland streams to the Pacific Ocean. With its eel-like boneless body, primitive gill holes, and suction-cup mouth ringed with sharp teeth, the Pacific lamprey is a creature from another era, virtually unchanged from its first appearance 500 million years ago. Although the Pacific lamprey currently has no economic value, it has historically been an important fish for Tribal peoples of the Pacific coast and interior Columbia River basin, who continue to harvest lamprey for subsistence, ceremonial, and medicinal purposes. PNNL began studying lamprey for the Corps of Engineers in 1999, even before environmental groups petitioned the U.S. Fish and Wildlife Service in January 2003 to list the species as endangered, citing a drop in numbers from 50,000 in the 1960s to less than 1,000 in the 1990s on the Snake River alone. The Service announced in January 2005 that it would decline the petition due to lack of information; however, it will continue to work with others on efforts to conserve lamprey and their habitats. In the Corps studies, PNNL investigated the swimming ability of the lamprey, their response to forces encountered in hydro turbine passage, and their behavior when encountering screens. Screens installed in turbine intakes to route juvenile salmon away from the turbines into juvenile bypass systems were suspected of posing a danger to the young lamprey. PNNL's studies found that juvenile Pacific lamprey, who are as wide as a pencil and about 5 inches long, are fairly weak swimmers. Their burst speed is half that of similar sized juvenile salmon (28.6 feet per second versus 58 feet per second) and their prolonged swimming speed is one-fourth that of juvenile salmon (0.5 feet per second versus 2 feet per second over a 15-minute period). Most juvenile salmon entering a turbine intake would never actually come in contact with the bypass screens but would use them like a guiding wall to go up into the juvenile bypass system. But in PNNL's laboratory studies, using the DOE-funded Aquatic Laboratory in Richland, all of the juvenile lamprey placed into a test flume made immediate contact with the screen at the end of the flume, at a water flow of 1.5 feet per second, much slower than the average 2.4 feet per second water velocity typically found at a turbine bypass screen. Within one minute, 70% of the lamprey were not just resting on the screen, they were stuck and many had gotten their tails wedged in the 1/8-inch spaces between the bars of the wire screen. This behavior was confirmed by field research PNNL conducted at operating dams using infrared underwater video. PNNL also found that lamprey proved remarkably hardy in laboratory shear and pressure stress tests. Lamprey showed no signs of injuries when exposed to a jet flume of water at velocities up to 60 feet/second, which are known to injure and kill salmon. This finding could imply that turbine passage is safer for lamprey than juvenile bypass system passage, according to PNNL project lead Russell Moursund. PNNL's laboratory trials and field observations also showed that lamprey were up to 50 times more likely to get stuck on screens with horizontally oriented bars than on those with vertically oriented bars. PNNL also compared different screen types and found that while 70% of the lamprey were impinged on the 1/8-inch screen, no juvenile lamprey were impinged on screens using a narrower bar spacing of 3/32-inch. Based on PNNL's studies, the Corps has decided that all new juvenile bypass screens installed at its dams should use 2/24-inch bar spacing rather than 1/8-inch bar spacing to protect migrating juvenile lamprey. For more information contact: Charlie Brandt, Resource and Ecosystem Management product line manager, or Russ Moursund, project scientist.

Page 877 of 1046

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