Kokanee Impacts Assessment and Monitoring on Lake Pend Oreille, Idaho, Annual Progress Report for October 1995-September 1996.
The purpose of this project was to Monitor Lake Pend Oreille's kokanee Oncorhynchus nerka kennerlyi population. Data will serve as a baseline for evaluating the benefits of a higher winter lake level beginning in 1996. We estimated the kokanee population in Lake Pend Oreille using a Hauser-type midwater trawl during August 1995 and September 1996. Population estimates in 1995 were 4.55 million age-0 kokanee, 2.87 million age-1 kokanee, 1.52 million age-2 kokanee, 0.74 million age-3 kokanee, 0.15 million age-4 kokanee, and 42,000 age-5 kokanee. Population estimates in 1996 were 5.42 million age-0 kokanee, 3.57 million age-1 kokanee, 3.17 million age-2 kokanee, 0.67 million age-3 kokanee, 0.44 million age-4 kokanee, and no age-5 kokanee. These were two of the highest total populations of kokanee since trawling began in 1977; largely due to high numbers of young kokanee. The densities of age-4 and 5 kokanee (which make up the bulk of the fishery), however, were the lowest on record in 1995 and average in 1996. We also surveyed traditional shoreline and tributary spawning areas. Counts of kokanee spawning in tributaries during 1995 were relatively consistent with previous years (6,261 kokanee). Counts of spawners along the shorelines reached a new record low of only 74 kokanee; a 93 percent decline from 1994. During December 1996, both counts dropped to their lowest point on record. Only 49 fish were seen spawning along the shorelines, and only 819 fish were seen in tributary streams. These low counts may have been partially due to higher lake levels during the spawning seasons. Higher than normal lake levels made additional gravel available for kokanee spawning in many areas of the lake. Possibly this caused kokanee to spread along the shorelines and reduced the spawner counts. Kokanee fry that had been fin clipped and stocked at the Cabinet Gorge Fish Hatchery Ladder in 1991 and 1992 returned at a rate of 0.27% and 0.14% once they matured. This return rate was much lower than the rate measured for kokanee released at Sullivan Springs. Different size groups of fry were stocked at Sullivan Springs in 1991 and 1992. The largest size group (60 mm total length) returned at the highest rate of 2.1% when they matured. Smaller fry (37 mm and 50 mm total length) returned at a rate of about 1.5%.
- Research Organization:
- Idaho Department of Fish and Game (IDFG)
- Sponsoring Organization:
- United States. Bonneville Power Administration.
- DOE Contract Number:
- 1997BI98065
- OSTI ID:
- 776427
- Report Number(s):
- DOE/BP-98065-1; Contract 1997BI98065; TRN: AH200120%%480
- Resource Relation:
- Other Information: PBD: 1 Sep 1998
- Country of Publication:
- United States
- Language:
- English
Similar Records
Lake Pend Oreille Fishery Recovery Project, 1998-1999 Annual Report.
Lake Pend Oreille Fishery Recovery Project, 1996-1997 Annual Report.