Drift Dynamics of Post-Hatch White Sturgeon in the Roosevelt Reach of the Columbia River during 2012-2014

The subpopulation of White Sturgeon Acipenser transmontanus in the Columbia River between Grand Coulee Dam (Washington) and Hugh Keenleyside Dam (British Columbia) has experienced chronic recruitment failure for nearly 40 years. Causes for recruitment failure are currently being investigated, but research has documented that White Sturgeon are producing viable progeny that are developing into the later free-embryo stages. To understand why recruitment is limiting, larval drift dynamics must be understood. Post-hatch White Sturgeon were collected nightly via benthic icthyoplankton nets during 2012-2014. Sturgeon were staged in the field and assigned to three overall stages: early-stage-free-embryo (EFE; stages 36-39); mid-stage-free-embryo (MFE; stages 40-43); and late-stage free-embryo (LFE; stage 44+). A total of 2,071 post-hatch White Sturgeon were captured in 2012 (10% EFE, 9.4% MFE and 80.6% LFE), 4,321 were captured (43.7% EFE, 25.2% MFE and 31.1% LFE) in 2013 and 12,335 (20.8% EFE, 17% MFE and 62.2% LFE) in 2014. Power peaking from upstream dams and raising of Lake Roosevelt to full pool was occurring during larval drift in all years. Ultimately, hydropower operations during larval drift could be limiting White Sturgeon recruitment in the Roosevelt Reach of the Columbia River.