Seasonal changes in distribution of coastal cutthroat trout in an isolated watershed

Graduation date: 2003In an effort to identify seasonal distribution patterns and habitat requirements of coastal\ud cutthroat trout Oncorhynchus clarki clarki, movement of tagged and marked individuals\ud (35 radio-tagged, 753 PIT-tagged, and 5,322 fin-clipped) was monitored over a 14-month\ud period in an isolated watershed in southwestern Oregon. Emigration out of the basin was\ud estimated with a rotating fish trap. Results showed that 70% of recaptured PIT-tagged\ud cutthroat trout and 86% of radio-tagged fish moved among channel units. A smaller\ud proportion of tagged fish moved at the reach- and segment-scale. Greatest movement\ud occurred in April, at the peak of spawning, and the least occurred in October, when\ud discharge was at its lowest. Radio- and PIT-tagged cutthroat trout occupied pool habitat\ud 62-97% of the time, depending on the season. Only 63 (< 1% of tagged and marked fish)\ud coastal cutthroat trout emigrated out of the study area between February and June. Results\ud suggested that unit-scale movement was common throughout the year, and reach- and\ud segment-scale movement was more important during the winter and spring. In addition,\ud habitats (e.g., pool, riffle, and cascade) occupied by coastal cutthroat trout change in\ud concert with discharge, water temperature, and life-history requirements (e.g., spawning,\ud refuge, and feeding)