Estimating Differences in Growth and Metabolism in Two Spatially Segregated Groups of Columbia River White Sturgeon Using a Field-Based Bioenergetics Model

Abstract

Recovery of white sturgeon in the Upper Columbia River continues to be limited by our understanding of the species' biology, including factors which influence growth, habitat selection and their interaction. Sampling challenges in large rivers coupled with limitations to invasive research on endangered species also create specific challenges to the de- tailed understanding of growth and metabolism. A new bioenergetics modelling approach which estimates basic parame- ters from field data, specifically length-increment and length-at-age data was therefore applied in order to provide novel insights into white sturgeon growth and metabolism. A large existing capture database was used to examine two groups of white sturgeon which preferentially occupy habitats in the transboundary section of the Upper Columbia River down- stream of Keenleyside Dam (HLK group) or further downstream near Waneta (WAN group). Successful application of the model showed differences in both growth and metabolism. Mean annual food intake appears similar for the two groups; however growth was more rapid for the HLK group. This resulted from a higher metabolic rate for the WAN group cou- pled with contrasts in seasonal food intake. Growth differences between groups lead to slower growth and later maturity for the WAN group. In aggregate, results suggest that the WAN group may be food limited and ultimately may have lower lifetime fecundity due its apparently later maturity and the possibility that lower energy intake might increase the interspawning interval. Finally, the functional structure of the model leads to concerns that both groups are approaching the thermal maxima for consumption, which may lead to reductions in body growth if increases in water temperature con- tinue. Overall, application of this bioenergetics model identified new avenues for study which should assist conservation efforts in this species.