12722 – Ecology of Kokanee Salmon and Rainbow Trout

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

Ecology of Kokanee Salmon and Rainbow Trout in Crater Lake, Oregon, with comments on long-term implications of fish introductions


Report Number: 12722

Permit Number: CRLA1992ADOU

Current Status: Checked in

Date Received: Jan 01, 1998

Reporting Year: 1992

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

Park-assigned Study Id. # CRLA1992ADOU

Permit Expiration Date: Jan 01, 1998

Permit Start Date: Jan 01, 1998

Study Starting Date: Jan 01, 1992

Study Ending Date: Jan 01, 1992

Study Status: Completed

Activity Type: Other

Subject/Discipline: Other

Objectives: The objective of this study was to develop a better understanding of the ecological role(s) of introduced fish in Crater Lake.

Findings and Status: Originally barren of fish, Crater Lake was stocked with approximately 1.8 million salmonids from 1888 to 1941. Rainbow trout and kokanee salmon are the only species of fish now known in inhabit the lake. Kokanee salmon exhibited cyclic patterns in population, age structure, condition, abundance, and biomass from 1985 to 1991. One dominant year class of relatively low abundance and high condition were present from 1985 to 1987. Multiple year classes with increasing abundance and decreasing condition were present from 1989 through 1991. Rainbow trout maintain a diverse population structure throughout the study with a trend toward a relative increase of older age classes and larger fish. Vertical and horizontal migrations of fish occurred with and between the nearshore and offshore zones of the lake. Kokanee fed primarily offshore on zooplankton and small bodied insects. Kokanee cropped the Daphnia population and altered zooplankton community structure during the study period. Rainbow trout fed nearshore on large bodied vertebrate and invertebrates. Introduced fish in Crater Lake exhibited the potential to impact limnetic and benthic community structure, nutrient flux with and between communities, and lake clarity.

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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