This research focused on features of a genetically
isolated population of cutthroat trout (Oncorhynchus clarki)
in the Triangle Lake basin of coastal Oregon. A falls at
the outlet of Triangle Lake has blocked upstream migration
of trout and anadromous salmonids into the basin. Cutthroat
trout were found throughout the six study streams of the
Triangle Lake basin in association with other native fishes
and introduced warmwater fishes. Warmwater species (e.g.
Centrarchidae) were restricted largely to the lakes of
Triangle Lake basin, and did not comprise a significant part
of the stream fish fauna. Salmonids and cottids dominated
the upper forested reaches of the basin, whereas nonsalmonids
dominated the lower reaches. The middle reaches
contained a transitional fish community between the upper
and lower reaches.
Reach type was a major factor influencing cutthroat
trout density and size distribution. Areal densities of
cutthroat trout were highest in the upper reaches and lowest
in the lower reaches with the exception of 0+ cutthroat
trout, which occurred at similar densities in all reaches.
The highest frequency of 1+ cutthroat trout occurred in the
middle reaches, whereas the highest frequency of 0+
cutthroat occurred in the lower reaches. Within reaches,
channel unit type influenced the density and age structure
of cutthroat trout. Pools and rapids had the highest
densities of cutthroat trout, whereas riffles, glides, and
cascades had lower densities. Larger trout were found
primarily in pools and rapids.
Planted steelhead fry (Oncorhynchus mykiss) were found
in two streams, Congdon Creek and Lake Creek. Although most
steelhead fry leave the basin as smolts, some steelhead
appear to become resident and may hybridize with native
cutthroat trout.
Cutthroat trout spawning was observed from late
December 1987 through late May 1988. Differences in the
time and place of spawning may serve to genetically isolate
two populations of cutthroat trout in Triangle Lake basin.
One population may be lake dwelling as adults and spawn
lower in the basin in late spring. The other population may
be stream dwelling and spawn in the winter during higher
flows, which allows them to spawn in the upper reaches of
the basin. / Graduation date: 1994
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36299 |
| Date | 22 June 1993 |
| Creators | Hurley, Steven M. |
| Contributors | Lamberti, Gary A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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