Use of infrared aerial photographs to identify and assess habitat needed by native fish in rivers

I assessed the use of color infrared aerial photographs as a tool to monitor habitat features in rivers needed by native fish. Several habitat features were identifiable in the photographs including backwaters, side channels, sand bars, riffles, and main channel. Error matrices were used to compare measurements of habitat features on aerial photographs to measurements made on the ground. Discharge and surface area of features appeared to affect the agreement between measurements from photographs and on the ground measurements. Spatial variation in occurrence of some habitat features was also observed over the length of the Bighorn River study area. Since construction of Boysen Dam, the main channel of the Bighorn River has been incised causing the loss of several habitat features important to fish. Losses of these habitat features have probably contributed to changes in fish assemblages within the Bighorn River.