First Documented Spawning of White Sturgeon in the Lower Willamette River, Oregon

White sturgeon (Acipenser transmontanus) in the lower Columbia River system were previously known to spawn in only one area; within the 12 km of mainstem Columbia River downstream of Bonneville Dam. Our work provides the first documentation of white sturgeon spawning in the Willamette River, Oregon, a major tributary of the lower Columbia River. We used artificial substrates to sample for white sturgeon eggs downstream of Willamette Falls from 18 May to 20 May 2009 and collected a total of 22 fertilized eggs. Embryonic developmental stages ranged front pigmentation change (Stage 2) to early epithelial (Stage 8), corresponding to fertilization times of approximately 5-17 hours prior to collection. We estimated that spawning occurred between 2100 hours on 19 May and 0900 hours on 20 May 2009, and that a minimum of three independent spawning events took place during that time. Results suggest that the area immediately downstream of Willamette Falls may be important white sturgeon spawning habitat, and that the lower Willamette River is likely an additional source of production for the white sturgeon population in the lower Columbia River system.