Ground Based Lidar and PIT Tags: Does High Resolution Data Improve Our Understanding of a Fish's Utilization of Habitat?

The Logan River and its tributaries in northern Utah are among the last remaining habitats that support a significant population of the imperiled Bonneville cutthroat trout (BCT - Oncorhynchus clarki Utah).  Efforts to protect and study the physical and biologic needs of BCT in the Logan River watershed include invasive species removal, habitat restoration through cattle exclosure, and fine scale habitat assessments.  The purpose of this study is to further our knowledge of BCT habitat utilization using microhabitat scale spatial data derived from ground based light detection and ranging (LiDAR), topographic and bathymetric Total Station (TS) surveys, and passive integrated transponder (PIT) tags. 

Many physical environmental assessments of in-stream habitat use population level spatial scales that do not describe the environment of an individual fish.  Fine scale (<.1 meter) measurements of the physical environment are needed to fully classify the in-stream habitat patches of Logan River tributaries.  Spatial data collected using ground based LiDAR has been used to measure stream width, bed slope, gravel distributions, and available cover at a scale indicating habitat use by individual fish.  Ground based LiDAR has also been used as an input in two-dimensional flow models to derive water velocity.  TS data has been used to measure water depth in habitat use locations.   

However, the physical in-stream environment cannot fully explain habitat utilization without considering biological interactions.   In the Logan River tributaries of Temple Fork and Spawn Creek, PIT tags have been used to identify the spatial distribution of BCT, brown trout (Salmo trutta), and brook trout (Salvelinus fontinalis).  Brown trout and brook trout have been shown to be superior competitors over BCT.  As a result, these fish segregate themselves into species specific habitat “hotspots” where high densities of fish have been observed over 3 years of PIT tag data.  Evaluating fine scale environmental characteristics from remotely sensed data at habitat hotspot locations allows for the assessment of species specific habitat use.  This combination of fine scale environmental spatial data and habitat utilization data provide insight into the environmental needs and/or limitations of BCT, brown trout, and brook trout.