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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