Bob Gresswell's Past Projects

Science Center Objects

Bob Gresswell's Past Projects

Evaluation of habitat restoration for the fluvial arctic grayling in the Big Hole River, Montana. Where do grayling and other fish go when the flowing waters of the upper Big Hole are relatively low and warm? To answer this question and better understand how habitat conditions affect the distribution of fish, researchers are using passive integrated transponder (PIT) technology to monitor fish movement and assess the effects of coldwater refugia on the distribution of fishes in the upper Big Hole River. Data will be used to evaluate the potential interaction of invasive fishes and climate change on the persistence of threatened Arctic grayling. The ultimate goal is provide information for planning and evaluating conservation projects in the watershed. 

Distribution, abundance, and movement of native cutthroat trout in the Snake River below Jackson Lake. We are using radio telemetry to determine distribution of Snake River finespotted cutthroat trout spawning populations and the physical characteristics of the Snake River that influence the relative abundance of spawners. According to preliminary analyses, individuals spawning in the same locations tend to occupy the same portions of the river before and after spawning. Research suggests that these fish exhibit complex behavioral strategies that connect spawning habitat in the watershed with movements across a range of spatiotemporal scales. The Snake River is not pristine, but it provides an excellent example of the importance of intact stream networks for supporting a full complement of behavioral patterns. 

Recolonization of Silver Bow Creek by westslope cutthroat trout (O. clarki lewisi) during Superfund remediation. More than a century of mining activity and unregulated waste disposal left the headwaters of the Clark Fork River, including Silver Bow Creek, devoid of fish until very recently. Major remediation efforts are scheduled for completion in 2012 and a stream that was fishless for many decades has begun to show signs of fish activity. We are examining the recolonization of Silver Bow Creek by tributary populations of westslope cutthroat trout and other native fishes currently occupying the watershed. The study will monitor fish movements within the tributaries and from the tributaries into Silver Bow Creek with the goal of identifying critical habitats of cutthroat trout, migration barriers, and other potential impediments to fish recovery in Silver Bow Creek. 

Landscape-scale effects of wildfire on the Colorado River cutthroat trout in the headwaters of the Colorado River, Colorado. The distribution and abundance of Colorado River cutthroat trout have declined from historical levels over their entire range. We are conducting coarse and fine-scale spatial analyses of debris flow potential and the spatial distribution and abundance of cutthroat trout in twelve high elevation headwater streams of the Colorado Rocky Mountains. Predictive models for debris-flow hazards are being applied before the occurrence of wildfires (with a projected burn severity distribution) to identify potentially susceptible drainage basins. Ultimately, results can be used to direct planning strategies to minimize effects from catastrophic fires in those areas and identify fish populations at risk of extirpation.