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Title: Assessment of Native Salmonids Above Hells Canyon Dam, Idaho, 2004-2005 Annual Report.

Abstract

In the western United States, exotic brook trout Salvelinus fontinalis frequently have a deleterious effect on native salmonids, and biologists often attempt to remove brook trout in streams using electrofishing. Although the success of electrofishing removal projects typically is low, few studies have assessed the underlying mechanisms of failure, especially in terms of compensatory responses. We evaluated the effectiveness of a three-year removal project in reducing brook trout and enhancing native salmonids in 7.8 km of an Idaho stream and looked for brook trout compensatory responses such as decreased natural mortality, increased growth, increased fecundity at length, or earlier maturation. Due to underestimates of the distribution of brook trout in the first year and personnel shortages in the third year, the multiagency watershed advisory group that performed the project fully treated the stream (i.e. multipass removals over the entire stream) in only one year. In 1998, 1999, and 2000, a total of 1,401, 1,241, and 890 brook trout were removed, respectively. For 1999 and 2000, an estimated 88 and 79% of the total number of brook trout in the stream were removed. For the section of stream that was treated in all years, the abundance of age-1 and older brookmore » trout decreased by 85% from 1998 to 2003. In the same area, the abundance of age-0 brook trout decreased 86% from 1998 to 1999 but by 2003 had rebounded to near the original abundance. Abundance of native redband trout Oncorhynchus mykiss decreased for age-1 and older fish but did not change significantly for age-0 fish. Despite high rates of removal, total annual survival rate for brook trout increased from 0.08 {+-} 0.02 in 1998 to 0.20 {+-} 0.04 in 1999 and 0.21 {+-} 0.04 in 2000. Growth of age-0 brook trout was significantly higher in 2000 (the year after their abundance was lowest) compared to other years, and growth of age-1 and age-2 brook trout was significantly lower following the initial removal years but recovered by 2003. Few other brook trout demographic parameters changed appreciably over the course of the project. Electrofishing removals required 210 person-days of effort. Despite experiencing slight changes in abundance, growth, and survival, brook trout in Pikes Fork appeared little affected by three years of intensive removal efforts, most likely because mortality within the population was high prior to initiation of the project such that the removal efforts merely replaced natural mortality with exploitation.« less

Authors:
;  [1]
+ Show Author Affiliations
  1. (Idaho Department of Fish and Game, Boise, ID)
Publication Date:
Research Org.:
Idaho Department of Fish and Game
Sponsoring Org.:
United States. Bonneville Power Administration.
OSTI Identifier:
903196
Report Number(s):
DOE/BP-00022947-1
R&D Project: 199800200; TRN: US200720%%208
DOE Contract Number:
00022947
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; ABUNDANCE; DISTRIBUTION; MORTALITY; PERSONNEL; REMOVAL; SHORTAGES; TROUT; WATERSHEDS; Trout - Idaho - Snake River, South Fork, Watershed - Counting

Citation Formats

Meyer, Kevin A., and Lamansky, Jr., James A.. Assessment of Native Salmonids Above Hells Canyon Dam, Idaho, 2004-2005 Annual Report.. United States: N. p., 2005. Web. doi:10.2172/903196.
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Meyer, Kevin A., & Lamansky, Jr., James A.. Assessment of Native Salmonids Above Hells Canyon Dam, Idaho, 2004-2005 Annual Report.. United States. doi:10.2172/903196.
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Meyer, Kevin A., and Lamansky, Jr., James A.. Mon . "Assessment of Native Salmonids Above Hells Canyon Dam, Idaho, 2004-2005 Annual Report.". United States. doi:10.2172/903196. https://www.osti.gov/servlets/purl/903196.
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@article{osti_903196,
title = {Assessment of Native Salmonids Above Hells Canyon Dam, Idaho, 2004-2005 Annual Report.},
author = {Meyer, Kevin A. and Lamansky, Jr., James A.},
abstractNote = {In the western United States, exotic brook trout Salvelinus fontinalis frequently have a deleterious effect on native salmonids, and biologists often attempt to remove brook trout in streams using electrofishing. Although the success of electrofishing removal projects typically is low, few studies have assessed the underlying mechanisms of failure, especially in terms of compensatory responses. We evaluated the effectiveness of a three-year removal project in reducing brook trout and enhancing native salmonids in 7.8 km of an Idaho stream and looked for brook trout compensatory responses such as decreased natural mortality, increased growth, increased fecundity at length, or earlier maturation. Due to underestimates of the distribution of brook trout in the first year and personnel shortages in the third year, the multiagency watershed advisory group that performed the project fully treated the stream (i.e. multipass removals over the entire stream) in only one year. In 1998, 1999, and 2000, a total of 1,401, 1,241, and 890 brook trout were removed, respectively. For 1999 and 2000, an estimated 88 and 79% of the total number of brook trout in the stream were removed. For the section of stream that was treated in all years, the abundance of age-1 and older brook trout decreased by 85% from 1998 to 2003. In the same area, the abundance of age-0 brook trout decreased 86% from 1998 to 1999 but by 2003 had rebounded to near the original abundance. Abundance of native redband trout Oncorhynchus mykiss decreased for age-1 and older fish but did not change significantly for age-0 fish. Despite high rates of removal, total annual survival rate for brook trout increased from 0.08 {+-} 0.02 in 1998 to 0.20 {+-} 0.04 in 1999 and 0.21 {+-} 0.04 in 2000. Growth of age-0 brook trout was significantly higher in 2000 (the year after their abundance was lowest) compared to other years, and growth of age-1 and age-2 brook trout was significantly lower following the initial removal years but recovered by 2003. Few other brook trout demographic parameters changed appreciably over the course of the project. Electrofishing removals required 210 person-days of effort. Despite experiencing slight changes in abundance, growth, and survival, brook trout in Pikes Fork appeared little affected by three years of intensive removal efforts, most likely because mortality within the population was high prior to initiation of the project such that the removal efforts merely replaced natural mortality with exploitation.},
doi = {10.2172/903196},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Aug 01 00:00:00 EDT 2005},
month = {Mon Aug 01 00:00:00 EDT 2005}
}
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DOI:  10.2172/903196
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  • ;
    Despite the substantial declines in distribution and abundance that the Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri has experienced over the past century, quantitative evaluations of existing population sizes over broad portions of its historical range have not been made. In this study, we estimate trout abundance throughout the Upper Snake River basin in Idaho (and portions of adjacent states), based on stratified sample extrapolations of electrofishing surveys conducted at 961 study sites, the vast majority of which (84%) were selected randomly. Yellowstone cutthroat trout were the most widely distributed species of trout (caught at 457 study sites), followed by brookmore » trout Salvelinus fontinalis (242 sites), rainbow trout O. mykiss and rainbow x cutthroat hybrids (136 sites), and brown trout Salmo trutta (70 sites). Of the sites that contained cutthroat trout, more than half did not contain any other species of trout. Where nonnative trout were sympatric with cutthroat trout, brook trout were most commonly present. In the 11 Geographic Management Units (GMUs) where sample size permitted abundance estimates, there were about 2.2 million trout {ge}100 mm, and of these, about one-half were cutthroat trout. Similarly, we estimated that about 2.0 million trout <100 mm were present, of which about 1.2 million were cutthroat trout. The latter estimate is biased low because our inability to estimate abundance of trout <100 mm in larger-order rivers negated our ability to account for them at all. Cutthroat trout were divided into approximately 70 subpopulations but estimates could be made for only 55 subpopulations; of these, 44 subpopulations contained more than 1,000 cutthroat trout and 28 contained more than 2,500 cutthroat trout. Using a logistic regression model to predict the number of spawning cutthroat trout at a given study site, we estimate that an average of about 30% of the cutthroat trout {ge}100 mm are spawners. We compared visually-based phenotypic assessments of hybridization with subsequent genetic analyses from 55 of the study sites and found that: (1) genetic analysis corroborated our visual determination that hybridization was absent at 37 of 55 sites; (2) at the seven sites where we visually failed to discern genetically-detected hybridization, the percent of rainbow trout alleles in the population was low (<1 %) at all but two locations; and (3) where we detected hybridization both visually and genetically (11 sites), levels of introgression were positively correlated between methods (r{sub 2} = 0.65). Based on this strong agreement, we phenotypically classified cutthroat trout as ''pure'' and ''{ge}90% pure'' at 81% and 90%, respectively, of the study sites within these GMUs. Our results suggest that, despite the presence of nonnative threats (genetic and competitive) in much of their current range in Idaho, Yellowstone cutthroat trout populations remain widely distributed and appear healthy in several river drainages in the Upper Snake River basin. Nevertheless, ongoing efforts to secure core cutthroat trout populations, protect areas from further nonnative invasions, and restore disturbed habitat are recommended for further protection of Yellowstone cutthroat trout in Idaho.« less

  • Native resident salmonids in the western United States are in decline throughout much of their range. The purpose of the multi-phased project is to restore native salmonids in the upper Snake River basin to self-sustaining, harvestable levels.

  • ;
    We investigated factors affecting the distribution and abundance of Yellowstone cutthroat trout (YCT), the abundance of all trout, and species richness in several drainages in the upper Snake River basin in Idaho. A total of 326 randomly selected sites were visited within the four study drainages, and of these, there was sufficient water to inventory fish and habitat in 56 of the sites in the Goose Creek drainage, 64 in the Raft River drainage, 54 in the Blackfoot River drainage, and 27 in the Willow Creek drainage. Fish were captured in 36, 55, 49, and 22 of the sites, respectively,more » and YCT were present at 17, 37, 32, and 13 of the sites, respectively. There was little consistency or strength in the models developed to predict YCT presence/absence and density, trout density, or species richness. Typically, the strongest models had the lowest sample sizes. In the Goose Creek drainage, sites with YCT were higher in elevation and lower in conductivity. In the Raft River drainage, trout cover was more abundant at sites with YCT than without YCT. In the Blackfoot River drainage, there was less fine substrate and more gravel substrate at sites with YCT than at sites without YCT. In the Willow Creek drainage, 70% of the sites located on public land contained YCT, but only 35% of private land contained YCT. The differences in variable importance between drainages suggests that factors that influence the distribution of YCT vary between drainages, and that for the most part the variables we measured had little influence on YCT distribution. n sites containing YCT, average cutthroat trout density was 0.11/m{sup 2}, 0.08/m{sup 2}, 0.10/m{sup 2}, and 0.08/m{sup 2} in the Goose Creek, Raft River, Blackfoot River, and Willow Creek drainages, respectively. In sites containing trout in general, average total trout density in these same drainages was 0.16/m{sup 2}, 0.15/m{sup 2}, 0.10/m{sup 2}, and 0.10/m{sup 2}. Models to predict YCT density, total trout density, and species richness were either weak (i.e., explained little variation) or contained small sample sizes. Based on our results, it appears that factors other than those we measured are affecting fish populations in these drainages.« less

  • ;
    We assessed the relationships between specific stream attributes and Yellowstone cutthroat trout Oncorhynchus clarki bouvieri distribution and biomass at 773 stream reaches (averaging 100 m in length) throughout the Upper Snake River Basin in Idaho, in an effort to identify possible limiting factors. Because limiting factors were expected to vary across the range of cutthroat trout distribution in Idaho, separate logistic and multiple regression models were developed for each of the nine major river drainages to relate stream conditions to occurrence and biomass of cutthroat trout. Adequate stream flow to measure fish and habitat existed at 566 sites, and ofmore » those, Yellowstone cutthroat trout were present at 322 sites, while rainbow trout O. mykiss (or rainbow x cutthroat hybrids) and brook trout Salvelinus fontinalis occurred at 108 and 181 sites, respectively. In general, cutthroat trout presence at a specific site within a drainage was associated with a higher percentage of public property, higher elevation, more gravel and less fine substrate, and more upright riparian vegetation. However, there was much variation between drainages in the direction and magnitude of the relationships between stream characteristics and Yellowstone cutthroat trout occurrence and biomass, and in model strength. This was especially true for biomass models, in which we were able to develop models for only five drainages that explained more than 50% of the variation in cutthroat trout biomass. Sample size appeared to affect the strength of the biomass models, with a higher explanation of biomass variation in drainages with lower sample sizes. The occurrence of nonnative salmonids was not strongly related to cutthroat trout occurrence, but their widespread distribution and apparent ability to displace native cutthroat trout suggest they may nevertheless pose the largest threat to long-term cutthroat trout persistence in the Upper Snake River Basin.« less

  • ; ;
    No abstract prepared.