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Adult Pacific Lamprey Trends and Abundance

Snake River Region

Adapted from Luzier, C.W., H.A. Schaller, J. K. Brostrom, C. Cook-Tabor, D.H. Goodman, R.D. Nelle, K. Ostrand, and B. Streif. 2011. Pacific Lamprey (Entosphenus tridentatus) Assessment and template for Conservation Measures. U.S. Fish and Wildlife Service, Portland, Oregon. 282 pp.

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Ice Harbor DamLittle Goose DamLower Monumental DamLower Granite Damealt_textalt_textalt_textClearwaterLower North Fork ClearwaterUpper North Fork ClearwaterLower Grande RondeLower SalmonSouth Fork ClearwaterMiddle Fork Clearwateralt_textUpper Grande RondeWallowaImnahaHells CanyonMiddle Salmon-ChamberlainLower SelwayUpper SelwayUpper SalmonLittle SalmonSouth Fork SalmonNorth Fork SalmonMiddle Salmon-PantherUpper Middle Fork SalmonPahsimeroiLemhi The uncertainty associated with estimating Pacific lamprey status and trends for many watersheds in the Snake River region is quite high due to the lack of targeted surveys, harvest records, and dam counts. Relying on best professional judgment, expansions of data from other species, and partial surveys for a limited area of the watershed, managers and researchers have estimated that up to 1,150 adult Pacific lamprey may comprise the Snake River region population. The managers and researchers also suggested that the short-term trend in abundance is severely declining. The highest threats to the long-term persistence of Pacific lamprey in the Snake River region have been identified as the Federal Columbia River Power System dams on the mainstem Snake and Columbia rivers and small effective population size. Several watersheds in the Snake River region that were historically occupied by Pacific lamprey are no longer accessible because impassable dams block Pacific lamprey migrations. Impassable dams include those from Hells Canyon Dam Complex to Shoshone Falls (Snake River), Dworshak Dam (North Fork Clearwater), and Wallowa Lake Dam. Other high priority threats include stream degradation, passage, and water quality.