Differences in spawning and emergence phenology between stocked and wild populations of brown trout in southwestern Wisconsin streams

摘要

The timing of spawning and emergence of stocked and wild populations of brown trout Salmo trutta in 9 streams in southwestern Wisconsin (USA) during autumn 1995 and spring 1996 was investigated. Stocked populations of brown trout had a median date of redd formation 10 days before wild trout, 75% of redds were constructed 12 days before those of wild trout. On average, alevins of stocked trout emerged 17 days earlier from redds constructed on the median date of redd formation than did alevins of wild trout. Compared with wild trout, alevins of stocked trout emerged 13 days earlier from redds made on the date of 75% redd formation. It is suggested that earlier autumn spawning and the accompanying earlier spring emergence of alevins influences reproductive success of the population and that timing of spawning should be carefully considered when selecting brown trout of wild or domestic origin to establish reproducing populations within streams.