"December 1995."

Includes bibliographical references (p. 32-33, 66-68)

Chapter 1 Paragamian, V.L., G. Kruse and V. Wakkinen Kootenai River white sturgeon spawning and recruitment evaluation

Chapter 2 Fredericks, J. and L. Fleck Estimating abundance of larval and advanced young-of-the-year sturgeon and burbot in the Kootenai River and Kootenay Lake

CHAPTER 1: The Kootenai River white sturgeon was listed as an endangered species on September 4, 1994. The U.S. Fish and Wildlife Service issued a formal Biological Opinion on the Kootenai River white sturgeon to the U.S. Army Corps of Engineers and Bonneville Power Administration in relation to spring discharge below Libby Dam. These agencies were asked in the Biological Opinion to work adaptively to obtain flow conditions that were conducive to white sturgeon recruitment. The U.S. Army Corps of Engineers, in agreement with Bonneville Power Administration, provided a release of 2.09 billion cubic meters (1.7 million acre-feet) of water above minimum flow from Libby Dam from April 29 to July 17, 1995. This release of water and local inflow provided up to 1,082 m3/s (38.2 thousand cubic feet per second [kcfs]) discharge in the Kootenai River at Bonners Ferry, Idaho, on May 18, 1995. This study was designed to monitor and evaluate these flow conditions for white sturgeon spawning and recruitment. Between February and early April 1995, a total of 38 adult sturgeon (13 males and 25 females) were monitored with radio and sonic telemetry, including 7 females and 6 males in known late vitellogenic stage. Two males and 11 females remained in Kootenay Lake during the experimental flow release. An additional 3 males and 3 females made brief movements out of the lake and into the lower river. The remaining 19 fish moved to locations upstream of Rock Creek (river kilometer [rkm] 215). Most of these sturgeon migrated to suspected spawning locations in the upper Kootenai River. Monitoring of the 1995 test flow indicated Kootenai River white sturgeon spawned, but we are still uncertain as to the survival of eggs and larvae. Two thousand one hundred and eleven mat samples collected 163 eggs. The majority (71 eggs) were collected in the Myrtle Creek section from rkm 233.5 to 234.7. Sixty-three were collected in the middle Shorty's Island section (rkm 229.6 to 231.5), 16 eggs were collected in the Wildlife Refuge section (rkm 228.0 to 229.5). One hundred twenty-seven (78%) of the eggs were viable. States of egg development ranged from 12 to 25, with 80% of the eggs at stage 20 or earlier. Most eggs were probably captured soon after spawning events. White sturgeon spawned during a minimum of 16 days of the 42-day test flow in 1995. Three distinct spawning intervals were noted; May 22 to 23, May 27 to June 6, and June 11 to 13, 1995. White sturgeon spawned in slow-moving water ranging from 0.06 to 1.2 m/s (0.2 to 3.9 ft/s) and averaged 0.18 m/s (0.6 ft/s) in sand substrate. This spawning habitat is thought to be unsuitable in comparison to habitat utilized by white sturgeon in the Columbia River. Sampling for juveniles from August 1, 1994 to August 31, 1995 resulted in a catch of 43 white sturgeon (33 in gill nets, 3 by rod and reel, and 7 on set lines). They ranged from 20 to 102 cm fork length and 35 to 120 cm total length. This catch included six wild sturgeon of the 1991 year class. We believe augmented discharge from Libby Dam should reach a minimum of 708 m3/s (25 kcfs). If local inflow were equal, the magnitude of flow at Bonners Ferry would nearly equal the 1991 discharge that produced the last notable cohort with the lowest discharge since Libby Dam was activated. We continue to recommend incremental increases in flow of 57 m3/s (2 kcfs). Much of the decision to initiate the augmented flow to stimulate sturgeon spawning will be based on the migration behavior of sturgeon and rise in river temperature to 9 C (48.2 F)

CHAPTER 2: We used a variety of sampling methods in an effort to determine if the higher spring flows during May and June of 1995 resulted in the production of larval and advanced young-of-the-year (YOY) white sturgeon (Acipenser transmontanus). We also attempted to sample the winter of 1994-95. Sampling commenced in April and extended through October 1995. Sampling equipment included conical larval fish nets, beam trawls, shrimp trawls, gill nets, hoop nets, minnow traps, electrofisher, beach seine, and rod and reel. We caught no larval sturgeon or burbot, and we caught no YOY sturgeon. One YOY burbot was captured in the lower Kootenai River in a baited minnow trap. We also caught 33 older juvenile sturgeon in small mesh gill nets, of which all but two were thought to be of hatchery origin. The minimum length captured in the gill nets was 35 cm total length (age 3+ to age 4+), which indicated that there were no sturgeon smaller than this in the system, or they are not recruited to the gill nets until they reach this length. The lack of success in sampling YOY sturgeon is not encouraging, and may be further evidence that sturgeon spawning is leading to very few juveniles. Although the methods we used have been proven effective in other systems, it is possible they are ineffective in the Kootenai system. We believe the gill nets can be used to effectively estimate the abundance of age 3+ and age 4+ sturgeon, and the flow tests can only be fully evaluated 3 to 4 years following the test, when recruits from flow test year classes are 30 to 40 cm.

Bonneville Power Administration DE-BI79-88BP93497 88-65