12706 – 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


Report Number: 12706

Permit Number: CRLA1991AADO

Current Status: Checked in

Date Received: Jan 01, 1998

Reporting Year: 1991

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

Park-assigned Study Id. # CRLA1991AADO

Permit Expiration Date: Jan 01, 1998

Permit Start Date: Jan 01, 1998

Study Starting Date: Jan 01, 1991

Study Ending Date: Jan 01, 1991

Study Status: Completed

Activity Type: Other

Subject/Discipline: Fish/Ichthyology

Objectives: Document and compare the ecology of kokanee salmon and rainbow trout in terms of length, weight, age, growth, food habits and distribution in Crater Lake.

Findings and Status: The kokanee population previously dominated by one age class, exhibited a multiple age class structure with a large age 2+ cohort in 1990, and large 2+ and 3+ cohorts in 1991. Age 2+ and 3+ kokanee were observed circling the lake, following the shoreline closely in schools as large as 200,000 during the day. Small schools of kokanee were observed in 1989, extensive schooling behavior, as observed in 1990 amd 1991, has not been observed for eight years. Schools of kokanee would disperse at dusk and were often observed feeding at the lake surface in the pelagic zone. Preliminary food habits analyses indicated that kokanee fed heavily on Cladocerans and fed less on small bodied aquatic and terrestrial insects. Rainbow trout continued to exhibit a more complex age structure and food habits regime. Predation on kokanee salmon by rainbow trout was recorded for the first time in many years. Spawning by rainbow trout was observed along the shoreline near Cleetwood Cove in mid-June, 1991. Analyses of age, growth, food habits and the ecology of each species relative to the limnological characteristics of the lake continue.

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: 2000

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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