Further Evidence of Size Gradients of Arctic Grayling (Thymallus arcticus) Along Stream Length

Previous work in Alaska indicates that the distribution of Arctic grayling (Thymallus arcticus) along streams is influenced by fish size. Larger fish are usually found in the upstream reaches, and the mean size gradually decreases further downstream, closer to the stream mouth. One of the hypotheses supporting this observation is that larger fish have a feeding advantage because they have first access to drifting prey. This mechanism is also believed to occur within pools. This extension note provides further evidence supporting the size gradient of Arctic grayling in streams. I use data from two rivers in northern British Columbia and one river in Alberta to show similar patterns of size distribution.