Lake Pend Oreille Fishery Recovery Project, 1998-1999 Annual Report.
- Idaho Department of Fish and Game, Boise, ID
The minimum water level of Lake Pend Oreille was raised from 625.1 m to 626.4 m elevation during the winter of 1998-99 in an attempt to recover the impacted kokanee Oncorhynchus nerka fishery. This report covers the third year of testing higher winter levels. Hydroacoustic surveys and mid-water trawling were conducted in the fall of 1999 to assess the kokanee population. We estimated the abundance of each age class of kokanee as: 6.023 million age-0 (wild and hatchery fry), 883,000 age-1, 409,000 age-2, 579,000 age-3, 861,000 age-4, and 87,000 age-5. Wild fry abundance was estimated at 2.57 million fish. These originated from 43.1 million eggs spawned in the wild during the fall of 1998. The survival from wild spawned eggs to wild fry was, therefore, 6.0%. This was lower than the 9.6% survival rate calculated last year but was much higher than the 1.4% calculated in 1995 prior to changing lake levels. To date, years of higher winter lake elevations have out-performed years of full drawdown. Based on data collected during trawl sampling, the total number of eggs laid in the lake in the fall of 1999 was 74.8 million. Mean fecundity per female was 379 eggs. Hatchery personnel collected 22.4 million eggs, leaving 52.4 million eggs to be laid by wild fish in tributary streams and along the lake shoreline. These eggs will be used to assess wild kokanee survival during 2000. Peak counts of spawning kokanee were 3,500 fish on the shoreline and 16,400 fish in tributary streams. This represents only a fraction of the total kokanee spawning population. Opossum shrimp Mysis relicta increased slightly in the southern two sections of the lake but decreased in the northern end. Immature and mature shrimp (excluding young-of-the-year shrimp) densities averaged 302 shrimp/m{sup 2}, down from 426 shrimp/m{sup 2} the previous year. The relatively stable shrimp population was not thought to affect the outcome of the lake level testing.
- Research Organization:
- Bonneville Power Administration, Portland, OR (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- 00004003
- OSTI ID:
- 796141
- Report Number(s):
- DOE/BP-98065-4; R&D Project: 199404700; TRN: US200213%%226
- Resource Relation:
- Other Information: PBD: 1 Dec 2001
- Country of Publication:
- United States
- Language:
- English
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