Seasonal movement patterns of stream-dwelling rainbow trout in north-central British Columbia, Canada

Movement forms an important part of salmonid life histories, and although previous studies have largely concluded that the majority of stream-dwelling salmonids are sedentary, the paradigm of restricted movement has been questioned by recent findings. We conducted a 3-year study to examine the seasonal movement patterns of rainbow trout Oncorhynchus mykiss in three small, lake-headed streams situated in north-central British Columbia and to determine whether movement was related to environmental conditions. Two of the three streams were subjected to streatuside clear-cut logging during the second year. The trout in our study streams generally remained sedentary during the summer, autumn, and winter seasons for a period of approximately 1-2 years before undertaking long-range (> 372-607-m) movements during springtime. These springtime long-range movements were most closely linked to stream discharge, as they generally ceased with the onset Of Summer low flows (< 10-20 L/s), but they did not resume in the autumn despite increasing flows. Links between movement patterns and stream temperature were less clear, as long-range movements occurred over a wide range (0-30 degrees C) of temperatures. The predominant direction of long-range movements was lakeward. All three streams supported relatively large populations of resident trout during the summer and autumn months; densities of 0.4-1.0 trout/dm(2) were primarily associated with age-0 to age-2 fish. Our data provide insights into how the movement patterns and life history strategies of stream-dwelling rainbow trout are intertwined, as well as how the timing of sampling efforts may be an important factor when assessing whether stream-dwelling fish are sedentary or mobile.