Factors influencing summer movement patterns of Bonneville cutthroat trout (Oncorhynchus clarkii utah)

We used multiple approaches to study summer movement patterns of Bonneville cutthroat trout (Oncorhynchus clarkii utah) in the Thomas Fork drainage of western Wyoming, USA. Our objectives were to (i) document summer movement patterns of cutthroat trout, especially as related to the concepts of local turnover and displacement distances, (ii) determine if fish size and condition were related to mobility, and (iii) compare summer movement patterns between years. Large fish (270-384 mm total length) monitored by radiotelemetry showed little movement during the summer as evidenced by a maximum displacement distance of <300 m and a low turnover rate among locations (0.21). For a broad size range of fish marked with visual implant tags (173-390 mm total length) in three study reaches, displacement distances were again low but turnover rate was high (>0.50 in most study reaches). This high turnover rate seemed to be driven mainly by movement among smaller fish as mobility declined with increasing fish size. Mobility also declined with decreasing body condition. Turnover rate in study reaches was higher during the summer of 1999 when stream flows were higher and water temperatures were cooler compared with the summer of 2000.