Reduced swimming performance and increased growth in domesticated rainbow trout, Oncorhynchus mykiss

Abstract

Domesticated populations of rainbow trout ( Oncorhynchus mykiss ) probably have been selected for high growth rates and large body size, which may have resulted in reduced sprint swimming performance. We hypothesized that more domesticated populations of rainbow trout would have higher growth rates and larger body size, but slower swim speed, relative to semiwild populations. We tested this hypothesis by measuring body mass, body length, and sprint swim speed multiple times over 92 days in progeny from crosses between males from three clonal lines and an outbred female. We found significantly higher body masses and significantly slower swim speeds in the highly domesticated Arlee and Hot Creek progeny groups compared with the semiwild Swanson hybrid progeny group, supporting our hypothesis. Growth rates also differed significantly among groups, but at the ages measured, the Swanson hybrid progeny had an intermediate growth rate. However, given the differences in body mass, either growth rates were higher in the more domesticated progeny groups at young unmeasured ages and (or) they hatched at a significantly larger body mass than the semiwild Swanson hybrid.