Brown Trout Spawn Timing, Redd Locations, and Stream Characteristics in Spearfish Creek within Spearfish, South Dakota, USA

Abstract

This study documented brown trout (Salmo trutta) spawning locations, redd construction timing, and associated environmental variables in an 850-m long mainstem section and a 400-m long diversion channel of Spearfish Creek within the city limits of Spearfish, South Dakota, USA in 2019. The first redds were observed on October 15, with no new redds observed after November 12. Redd construction peaked during the first week of November, when 23 redds were observed in the mainstem section and 50 in the diversion channel. Substrate size was significantly smaller, water temperatures significantly higher, and water velocities significantly greater in redd versus non-redd locations in both the mainstem reach and the diversion channel (P < 0.05). Six significant redd hotspots were observed in the diversion channel. Hotspots were associated with a small (0.1˚C), but significant, increase in water temperature from the rest of the channel locations. This is the first study to document redd locations in Spearfish Creek and will provide a baseline to evaluate future spawning activity, particularly as it may be affected by likely future anthropogenic changes potentially affecting the stream environment.