Cooperative Fish and Wildlife Research Units Program: South Dakota
Education, Research and Technical Assistance for Managing Our Natural Resources

South Dakota Project

Influence of fish density on growth rate of brown trout in Spearfish Creek, South Dakota

July 2016 - August 2018


Participating Agencies

  • South Dakota Game, Fish & Parks

Growth rate of Brown Trout is known to be density-dependent in stream systems. In Spearfish Creek, South Dakota, recent work has shown that mean biomass of Brown Trout >200 mm is about three times greater than that in Castle or Rapid creeks. However, adult Brown Trout in Spearfish Creek are about 30% smaller (220 mm) than similarly aged fish in Rapid Creek (315 mm). Because angler harvest of Brown Trout is generally low in Spearfish Creek, management options for increasing the size structure of the trout population may be limited. Catch and release regulations, for example, would exacerbate problems with small size of adult fish when growth rate is density-dependent; in contrast, liberalized regulations may have limited effect due to low angler harvest and(or) the social stigma associated with harvesting naturalized trout. From a management perspective, experimental manipulation of Brown Trout abundance shows promise as an approach for increasing the growth rate of stream-dwelling trout. Working with the South Dakota Department of Game, Fish & Parks and the U.S. Forest Service, the purpose of this project is to evaluate the growth response of Brown Trout to localized reductions of fish density in Spearfish Creek.