Kootenai River White Sturgeon Investigations; White Sturgeon Spawning and Recruitment Evaluation, 2004-2005 Annual Report.

Abstract

The objective of this research was to determine the environmental requirements for successful spawning and recruitment of the Kootenai River white sturgeon Acipenser transmontanus population. Annual tasks include monitoring and evaluating the response of various life stages of Kootenai River white sturgeon to mitigation flows supplied by the United States Army Corps of Engineers (USACE). Sampling for adult Kootenai River white sturgeon in 2004 began in March and continued into May. One hundred forty-two adult white sturgeon were captured with 4,146 hours of angling and set-lining effort in the Kootenai River. Kootenai River discharge and stage at Bonners Ferry in 2004 peaked in mid December. Discharge remained below 400 cubic meters per second (cms) until June 1; then, because of a systems operations request (SOR), increased and remained between 480 and 540 cms through the end of June. From July through September, discharge ranged from 360 to 420 cms, decreasing to 168 cms by the end of October. Discharge increased again to above 625 cms by November 4 to increase winter storage in Lake Koocanusa and ranged from 310 to 925 cms through the end of December. We monitored the movements of 31 adult sturgeon in Kootenay Lake, British Columbia (BC) and the Kootenai River from mid-March until late August 2004. All telemetered fish were dual tagged with external sonic and radio transmitters, and some of the fish were tagged in previous years. Eighteen of the 31 telemetered adult white sturgeon were released at Hemlock Bar reach (rkm 260.0) as part of a research project to test the feasibility of moving sexually mature adult white sturgeon to areas with habitat types thought to be more suitable for successful egg hatching and early life stage recruitment. Marked fish were monitored from the time of release until they moved downstream of Bonners Ferry. Sampling for white sturgeon eggs with artificial substrate mats began May 3 and ended June 10, 2004. We sampled 650 mat days (a mat day is one 24 h set) during white sturgeon spawning. Most of the sampling occurred in the post-Libby dam spawning reach (rkm 229.0 to 246.0) but some sampling occurred near Crossport (rkm 253.5) and in the Canyon reach above Hemlock Bar (rkm 261.0). We collected eight white sturgeon eggs near Shortys Island in 2004. Sampling for larval white sturgeon began June 8 and continued until July 22, 2004. Sampling occurred primarily at Ambush Rock (rkm 244.0) in an attempt to document any recruitment that might have occurred from the Set and Jet Program. We collected 103 larval fish, but none were white sturgeon larvae or embryos. Juvenile white sturgeon sampling started July 26 and continued through September 27, 2004. A total of 271 hours of gillnetting effort captured 256 juvenile hatchery white sturgeon and two juvenile wild white sturgeon.