12812 – Ecology of Kokanee Salmon and Rainbow Trout in Crater Lake, Oregon

Investigator’s Annual Reports (IAR’s) for Crater Lake National Park

Ecology of Kokanee Salmon and Rainbow Trout in Crater Lake, Oregon


Report Number: 12812

Permit Number: CRLA1997ASPG

Date Received: Jan 01, 1998

Reporting Year: 1997

Principal Investigator: Mark Buktenica, National Park Service, Crater Lake, Oregon

Park-assigned Study Id. # CRLA1997ASPG

Permit Expiration Date: Jan 01, 1999

Permit Start Date: Jan 01, 1998

Study Starting Date: Jan 01, 1997

Study Ending Date: Jan 01, 1997

Study Status: Completed

Activity Type: Other

Subject/Discipline: Ecology (Aquatic, Marine, Terrestrial)

Objectives: Develop a better understanding of the ecological role(s) of introduced fish in Crater Lake.

Findings and Status: Fish distribution was evaluated in 1996 and 1997 with sonar (BioSonics DT4000 and DT6000 respectively). The lake was divided into nearshore (0 to 100 m depth) and offshore (> 100 m depth) zones for purposes of the acoustic survey. In 1996 the fish population was estimated to be 56,500 with a density of 10.37 fish/ha. Density was highest nearshore, day and night; however, density offshore more than doubled during the day (4.0 to 8.9 fish/ha), while density nearshore decreased (34.4 to 21.8 fish/ha). Fish were detected deeper during the day (61.0% below 60 m) than at night (0.5% below 60 m). In 1997 several fish were detected below 120 m in depth. The maximum depth of detection was 146 m. The distribution of fish appeared to be most closely related to fish food habits. A multivariate analysis of variance indicated that kokanee salmon and rainbow trout food habits, collected over a twelve year period, were different (f = 51.12 with 31, 1222 d.f.). Kokanee salmon fed on fewer taxonomic food groups than rainbow trout. Kokanee fed on a large number of food items (average number of food items per stomach = 1074) of small body size (1.72 mg dry weight), primarily from the mid-water column. Rainbow trout fed on taxa taken from the lake bottom and the lake surface, with an average of 180 food items per stomach that averaged 11.06 mg dry weight.

For this study, were one or more specimens collected and removed from the park but not destroyed during analyses? No

Funding provided this reporting year by NPS: 4000

Funding provided this reporting year by other sources: 0

Full name of college or university: n/a

Annual funding provided by NPS to university or college this reporting year: 0


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