Population Status of White Sturgeon in the Lower Columbia River within Canada

Abstract

Abstract The subpopulation of white sturgeon Acipenser transmontanus in the Canadian portion of the Columbia River between Hugh L. Keenleyside Dam and the U.S.‐Canada border has been identified as endangered, with nearly 30 consecutive years of consistent recruitment failure. The objectives of this study were to determine the status and population attributes of this subpopulation. We estimated survival rates and abundance using catch‐curve analysis and mark‐recapture models. An annual survival rate of 89% (95% confidence interval [CI], 88‐90%) was estimated for the subpopulation using catch‐curve analysis for the time period 1993‐2004. The survival rates estimated from the mark‐recapture data were obtained using model‐averaged parameter estimates from a multistrata Cormack‐Jolly‐Seber model. The annual survival rate from the mark‐recapture model was estimated at 97% (95% CI, 92‐99%) from 1993 to 2004. The mark‐recapture methods estimated abundance for 2004 to be 1,157 individuals (95% CI, 414‐1,900). The mark‐recapture data suggest that the white sturgeon have low migration rates, ranging from 3% to 5% among sections of the river. Despite high estimated survival, high uncertainty as to the future viability of the white sturgeon subpopulation in this portion of the river remains, as natural recruitment is poor. The fish continue to age, and size and age‐frequency data suggest that recruitment failure continues in this subpopulation with minimal presence of wild juvenile or subadult white sturgeon detected.