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Idaho Department of Fish and Game Bull Trout Status Review and Assessment in the State of Idaho, December 20, 2004. (Part II of 2-- GIS files and assessment protocols) [See the 'Part I' entry for tabular data, reports, and maps]

Data Categories presence, historical presence, barriers, status review
Dates of Data 1800 TO 2004
Data Set Status Complete
Data Set Update Schedule Irregularly
Date Data Set Published on StreamNet Data Store 2/10/2005
Project Name & Number
Purpose of Data Set Purpose provided in Abstract
Summary / Abstract Broad-scale declines in bull trout Salvelinus confluentus distribution and abundance over the past century or more led to state-wide no-harvest regulations in the state of Idaho in 1994, and ultimately to a threatened listing under the Endangered Species Act in 1998. Despite this listing, quantitative evaluations of trends in abundance and estimates of existing population sizes over most of its historical range have not been made. We evaluated long-term trends in bull trout abundance, estimated population sizes, and conducted population viability analysis (PVA) for bull trout in Idaho, based on stratified sampling extrapolations of fish surveys (snorkel and electrofishing) conducted at 2,287 study sites scattered across 77,447 km of stream within seven recovery units in Idaho. Bull trout were present in 871 (38%) of the study sites, and were most likely to be observed or captured in 1st- and 2nd-order streams. Long-term trend estimates from bull trout redd counts, spawning weirs, and snorkel and electrofishing population surveys indicate that many bull trout populations declined through the mid-1990s when state-wide no-harvest regulations were implemented, but in general have increased over the last 10 years. Moreover, abundance of all other salmonid species appeared to increase at the same time, suggesting that increases in bull trout abundance on a broad scale were not related to the no-harvest rule. Bull trout abundance was positively correlated with the abundance of all other salmonids (including non-native brook trout), but was most strongly correlated with westslope cutthroat trout abundance. We estimated there was approximately 1.24 million bull trout divided between 269 designated local populations within the seven recovery units. Population viability analysis (PVA) indicates that if the general trend observed for the last 10 years is representative, or if populations reach equilibrium at levels near the current estimated abundance, all 7 recovery units have > 0.95 probability of at least one local population persisting 100 years. If local populations in the Kootenai River and Coeur d'Alene Lake basins experience negative growth with high variance, then there is a 0.30 and 0.20 probability of persistence, respectively, for at least one bull trout local population persisting 100 years containing 100 individuals. Our results suggest that bull trout remain relatively abundant in large stream networks throughout Idaho, that their abundance for most core areas in most recovery units has been increasing over the past decade, and that their risk of extirpation in Idaho is quite low.
Broad Biological Groups Fishes
Taxa Bull trout (Salvelinus confluentus)
Brook trout (Salvelinus fontinalis)
Location Idaho, Nevada, Kootenai River, Pend O'reille River, Spokane River, Couer d'Alene River, Clearwater River, Snake River, Salmon River, Weiser River, Payette River, Bruneau River, Little Lost River
NPCC Subbasins (2001 Subbasins) Blue Mountain: Snake Hells Canyon
Intermountain: Coeur d'Alene
Intermountain: Pend Oreille
Intermountain: Spokane
Middle Snake: Boise
Middle Snake: Bruneau
Middle Snake: Payette
Middle Snake: Weiser
Mountain Columbia: Kootenai
Mountain Snake: Clearwater
Mountain Snake: Salmon
Upper Snake: Snake upper closed basin
Keywords bull trout, salvelinus confluentus, presence, distribution, range, current, historic, 2004, circa 1800, Idaho, Nevada, Status Review
Lead Person and Organization That Created the Data Set Evan Brown
Other Participating Organizations Avista Corp., Idaho Dept. of Fish and Game, Idaho State University, Montana Dept. of Fish, Wildlife, & Parks, Nevada Dept. of Wildlife, NOAAF, Idaho Office of Species Conservation, Potlatch Corp., University of Idaho, USBLM, USBR, USFS, USFWS
Contact Person for Questions About the Data Name:  Evan Brown
Position:  Fisheries Database Manager
Organization:  Idaho Department of Fish and Game
Address:  P.O. Box 25 600 S. Walnut St.
Boise, ID  83707
Phone:  208-287-2721
email:  Send a note to addressed for evan.brown.
Broad Category of Methods Field
Data Collection Methods First, the historical range that was occupied by bull trout at the time of the first European exploration of the Northern Rocky Mountains will be estimated. Second, the current distribution, density and genetic status information for bull trout will be developed and displayed on a mapping segment basis. Lastly conservation populations, either as isolated and meta-populations (networked or connected populations - e.g. interbreeding populations) will be identified and population viability risk, genetic risk and disease risk assessments will be made for each of these populations. Risk will be assessed at three levels: 1) risk of genetic introgression, 2) risk associated with disease and 3) general population level risk. Risk assessments represent relative determinations indicating a higher or lower level of concern. The mapping and risk assessments will be completed for all populations, including those associated with lakes (adfluvial), that are maintained by natural reproduction.
The above data was compiled in the ArcView 3.2 BullMapper.apr. That data was summarized in the MS Access BullCon1.mdb. The report and protocol
File Formats MS-Word (.doc); ESRI shape files
Data structure description See data set files
URL where updated data may be available
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Papers, reports, and presentations that were done under this project. Bull Trout Assessment Protocol.doc, IDFG Bull Trout Status Review and Assessment in the State of Idaho, December 20, 2004, Status of Westslope Cutthroat Trout in the United States: 2002.
Restrictions or legal prerequisites for accessing and using this data set. No

File Size: 50 MB