Spawning-related movement patterns of a unique rainbow trout (Oncorhynchus mykiss) population in a South Dakota headwater stream

Abstract

The objectives of this study were to determine the spawning locations and movement patterns, and provide insight to the success of a naturalized rainbow trout (Oncorhynchus mykiss) population that occurs in a 3 km section of Spearfish Creek, South Dakota. Twelve rainbow trout from Spearfish Creek, South Dakota were implanted with radio transmitters and tracked from 6 December 2006 to 19 June 2007. Initiation of rainbow trout spawning-related movement was correlated with increasing discharge (r = 0.65, p = 0.0009). Mean gross movement was significantly lower during the pre-spawn period (mean = 236 m, SE = 59) compared with the spawning period (mean = 1661 m, SE = 313) (Kruskal–Wallis, F 1,30 = 56.3, p < 0.0001). Mean net movement was 25 m during the pre-spawn period and −9 m (downstream) during spawning. All rainbow trout used in this study moved into Cleopatra Creek (a tributary of Spearfish Creek) during the spawning period even though other nearby tributaries was available. The presence of brown trout (Salmo trutta) in the other tributaries is a possible reason why the rainbow trout did not use those areas for spawning.