P-96 Spatial Distribution and Species Segregation of Bonneville Cutthroat Trout, Brown Trout, and Brook Trout

Ryan Lokteff , Watershed Sciences, Utah State University, Logan, UT
Joe Wheaton , Watershed Sciences, Utah State University, Logan, UT
Brett B. Roper , Stream and Aquatic Ecology Center, USDA Forest Service, Logan, UT
Availability of Bonneville cutthroat trout (BCT - Oncorhynchus clarki Utah) habitat continues to decline in the Great Basin due to a lack of stream connectivity, over allocation of water resources, and detrimental land use practices.  The Logan River and its tributaries in northern Utah are one of the last remaining systems supporting a significant population of this imperiled fish.  BCT habitat selection, migration, and spawning are being studied in the tributaries of Temple Fork and Spawn Creek using Passive Integrated Transponder tags (PIT) and daily spawning surveys.  The purpose of this study is to evaluate patterns of BCT habitat utilization based on PIT tag location data. Persistent habitat hotspots have been identified using PIT tag and spawning survey coordinates over multiple years.   Habitat and spawning locations also help to identify seasonal habitat utilization patterns and movement. 

Assessment of BCT habitat utilization is complicated by biological components of competition and predation by brown trout (Salmo trutta) and brook trout (Salvelinus fontinalis) present in the system.  It has been shown that these two species are superior competitors over BCT.  PIT tags have also been used to track the movements and habitat utilization of these two species with respect to BCT.  Evaluating the spatial density of all three species through time provides insight into how habitat preferences and competitive components affect species distributions. 

Results show that the three species segregate themselves and rarely occupy the same locations even across time.  In Spawn Creek, BCT and brown trout are found over the full length of the stream.  BCT habitat utilization and spawning “hotspots” occur in different locations when compared to habitat utilization “hotspots” of brown trout.  Not surprisingly, brook trout are only found in the upper reaches of Spawn Creek in beaver ponds.  In Temple Fork, where brook trout are absent, BCT are predominantly found in the upper reaches and in beaver ponds.  There is a clear break in habitat utilization by brown trout in Temple Fork where the valley width constricts and slope increases.  Interestingly, movement patterns of BCT and brown trout also show that BCT have readily passed beaver dams while brown trout rarely pass beaver dams.  These results can also be used to show how BCT, brown trout, and brook trout distributions are influenced by the physical environment.  Some combination of environmental needs and/or limitations are combined with biological and behavioral effects to help explain the spatio-temporal distributions of these fish.