Dworshak Dam Impacts Assessment and Fisheries Investigation, 1991-1992 Progress Report.
Lake Pend Oreille, 38,000 hectares, is Idaho`s largest natural lake. Fisheries for kokanee Onchorynchus nerka, rainbow trout Onchorynchus mykiss, and bull trout Salvelinus confluentus have gone through major declines over the last 40 years. To date, the decline in kokanee abundance has not been fully explained. Water level management may be the single largest contributing factor to this decline. Two aspects of water level management appear critical. Dropping water level once kokanee spawning has occurred wall correlated with poor fishery harvest five years later (r = -0.71) (alpha = 0.005). Secondly, dropping the water level more than 2 m immediately before spawning leaves wave-washed gravel high on the bank and forces kokanee to spawn in low quality substrates, which again reduces survival. Changes in water level management coincided with the sharp declines in the kokanee fishery during the 1960s. Although the water level has been stabilized once spawning has occurred, the deep drawdowns resulting in poor spawning substrates continues to cause problems for the kokanee population. Recognizing the importance of these two factors gives hope that changes in water management can reverse the 30-year trend of declining kokanee populations before they are lost from the system. The authors recommend an experimental test of higher winter lake elevation for several years to document potential changes in kokanee abundance.
- Research Organization:
- Idaho Department of Fish and Game (IDFG)
- Sponsoring Organization:
- United States. Bonneville Power Administration.
- DOE Contract Number:
- 1987BP35167
- OSTI ID:
- 10119298
- Report Number(s):
- DOE/BP-35167-4; ON: DE94006086; TRN: 94:001670
- Resource Relation:
- Other Information: PBD: Nov 1993; Related Information: Dworshak Dam impacts assessment & fisheries investigations : annual report 1992 / prepared by Merlo [i.e., Melo] Maiolie, Steve Elam. -- Cover page.
- Country of Publication:
- United States
- Language:
- English
Similar Records
Kokanee Impacts Assessment and Monitoring on Lake Pend Oreille, Idaho, Annual Progress Report for October 1995-September 1996.
Kokanee Impacts Assessment and Monitoring of Lake Pend Oreille and Dworshak Reservoir, Idaho, 1994 Annual Report.