We reviewed the potential cumulative effects of human activities on bull trout in the Flathead Lake and River system of northwest Montana. Bull trout are the largest fish native to the Flathead drainage, attaining a length of up to one meter and a weight of 10 kg. This species migrates from Flathead Lake up to 250 km upstream to spawn in cold headwater tributaries with groundwater upwelling and clean gravels. Spawning and rearing habitats are limited and vulnerable to damage by deposition of fine sediments. Potential threats to bull trout habitat and populations include timber harvest, road building, mining, residential and agricultural development, hydropower construction and operation, harvest of fish by anglers, and non-native fish species. Management and mitigation options include application of best management practices and riparian guidelines for logging, habitat protection and improvement, improved fish passage to blocked areas, fishing regulations and integrative management of fish populations. Because of reduction in habitat, continued potential for habitat degradation, and limited options for management, the bull trout population is vulnerable and should be closely monitored to detect signs of decline. KEY TERMS: Migratory bull trout; spawning and rearing habitat; land management; sediment deposition; hydropower development; fisheries management and mitigation options.^D 0°m^S COLLECTS WV 2 r m DramXTICW Montana STA rr^" ti^N A >to6N 6
MklP-J998The studies leading to this report were supported in part by a financial grant from the Anaconda Minerals Company. Funds received were used to hire five temporary personnel over an 18 month period to assist in research programs. Without the additional manpower the programs would have been severely reduced or eliminated. The individual interest and assistance of AMC employees John Spindler,
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