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Bull Trout Trends and Abundance*

(DRAFT)

Blackfoot Core Area

Abundance: 250-1,000
Trend: Increasing

In the Black River Core Area, dams, past land use activities, transportation networks, and previous fisheries management practices have resulted in conditions that are limiting bull trout abundance and productivity.

Dams have fragmented bull trout populations in the core area and prevent migrations, as well as impact habitat by affecting reservoir and lake levels, water temperature, and water quality. Irrigation storage dams have fragmented watersheds, limited migrations, altered nutrient and sediment balances, changed and downstream flow patterns, and altered temperature regimes.

Forestry practices have impaired bull trout habitat throughout the core area. Legacy effects include increased sediment in streams, increased peak flows, hydrograph and thermal modifications, and loss of in-stream wood and of channel stability. Logging roads have led to increased sediment loads, channelization, valley bottom restriction, and increased accessibility for anglers and poachers.

Agricultural practices have led to conditions that limit bull trout abundance and productivity. Impacts from agriculture include dewatering, irrigation entrainment, reduced water quality, loss of riparian habitat, and increased water temperature.

The legacy effects of old transportation systems have led to conditions that are limiting bull trout in this core area. Past activities resulted in channelization and meander cutoffs, passage barriers, sediment production, unstable slopes, improper maintenance, and high road densities.

Effects associated with mining will continue to impact bull trout. Habitat and water quality impairments are contributing to the suite of factors limiting bull trout abundance and productivity.

Residential development and sprawl are threats to bull trout in this core area. Continued development will increase the demand for flood control, stream crossings, water diversion or withdrawal, and other stream channel alterations that are potentially harmful to bull trout.

Historic releases of non-native fish has led to competition and hybridization, which have reduced bull trout abundance and productivity. Expansion of non-native species populations is problematic since there are a limited number of acceptable methods to remove the fish. In addition, there is public opposition to controlling or eliminating non-native sport fisheries.



*The abundance and trend estimates are from the information provided in the USFWS 5-Year Review. For a comprehensive review of the estimated abundance and trends, please refer to U.S. Fish and Wildlife Service. 2008. Bull Trout (Salvelinus confluentus) 5-Year Review: Summary and Evaluation. U.S. Fish and Wildlife Service. Portland, OR. 55 pp.

For a comprehensive review of the limiting factors affecting bull trout in this Core Area, please refer to:
http://www.fws.gov/pacific/bulltrout/RP/Chapter_3%20Clark%20Fork.pdf

Adapted From:
U.S. Fish and Wildlife Service. 2002. Chapter 3, Clark Fork River Recovery Unit, Montana, Idaho, and Washington. 285 p. U.S. Fish and Wildlife Service. Bull Trout (Salvelinus confluentus) Draft Recovery Plan. Portland, OR.