Long-term population dynamics and conservation risk of migratory bull trout in the upper Columbia River Basin

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Conservation of migratory and sensitive fish like bull trout will require ecosystem level approaches that target stressors in headwater spawning and rearing habitats as well as critical habitats in rivers and lakes used during juvenile and adult life stages.

Bull trout in the Flathead River.

Bull trout in the Flathead River.

(Public domain.)

Freshwater fishes are increasingly imperiled due to cumulative effects of numerous human activities. Long-term monitoring data that accurately depict population status and risk are critical for assessing trade-offs in resource allocation to protect, conserve and recover imperiled species. Bull trout are listed as a threatened species under the Endangered Species Act in the United States, primarily due to ongoing habitat loss, invasive species, and climate change.

In this study, USGS fisheries scientists used extensive, long-term redd count (spawning nest) data from 88 local and regional bull trout populations in the upper Columbia River Basin, USA, to evaluate population dynamics and assess conservation risk.  Most bull trout populations had relatively low abundances (<20 redds annually) and were either stable or declining, with little evidence for increasing abundances. This is concerning given that many bull trout populations are depressed relative to historic levels and most populations will likely experience increasing pressures from future human activities. Moreover, conservation risk varied across watersheds and population attributes, suggesting that conservation management actions needed to recover this species will vary across watersheds and populations.  

 

The study, Long-term population dynamics and conservation risk of migratory bull trout in the upper Columbia River basin, was published online in the jounral Canadian Journal of Fisheries and Aquatic Sciences.

For more information, contact Ryan Kovach, 505-231-6692, rkovach@usgs.gov