Generation-scale movement patterns of cutthroat trout (Oncorhynchus clarkii pleuriticus) in a stream network

Abstract

Movements by stream fishes have long been the subject of study and controversy. Although much discussion has focused on what proportion of fish adopt mobility within particular life stages, a larger issue involves the lifetime movements of individuals. I evaluated movements of different sizes and ages of Colorado River cutthroat trout ( Oncorhynchus clarkii pleuriticus ) using a variety of sampling methods from 1996 to 2001 in a 40 km network of main-stem and tributary segments of the North Fork Little Snake River, Wyoming, USA. The probability of movement was related to the period of observation, initial location, and possibly individual growth rate, whereas distance moved was related to fish size and initial location. Furthermore, it appeared that movements by juveniles were mostly downstream, whereas those of older fish were largely upstream. Movement of cutthroat trout in this basin appeared to be driven by ontogenetic changes in habitat use and variation in habitat productivity. Given that this stream network exemplifies the complexity typical of many mountain watersheds, movement as a life history tactic in fishes may be more common than is sometimes recognized.