Rocky mountain sculpin swimming activity in a three-chambered flume

Rocky Mountain Sculpins are an imperiled species endemic to a restricted geographic distribution between Montana and Alberta. They occupy rivers with distinct seasonal flow regimes: one is relatively fast (St. Mary), one is relatively slow (Lee Creek), and one is intermediate (N. Milk River). Sculpins from St. Mary and Lee Cr. were endemic; those from N. Milk were likely introduced. We caught fishes from each location, transported them back to the University of Alberta, and acclimated them to holding conditions. We then tested their swimming behaviour in a three-chambered flume (details of the flume can be found in https://doi.org/10.1007/s10641-011-9867-2). The flume consisted of upstream and downstream boxes connected by a 1 m swim tunnel. Upstream and downstream place preference was recorded over 24 hours, and flow speed within the flume was increased in 15 cm/s steps over the course of a day. The willingness of the sculpins to move, as well as to travel in the swim tunnel, were recorded. All time spent moving (active) and stationary were noted throughout. The three subpopulations differed in time spent in the upstream and downstream locales, indicating behavioral adaptation to the different flow regimes. There was also evidence of individual fish that were highly exploratory, suggesting the presence of unique phenotypes within the species. The data suggest that sculpins have behavioral differences that likely reflect life in their unique riverine habitats.