Waldo Lake, located in the Oregon Cascades, is
considered to be one of the most dilute lakes in the
world. Even with very low nutrient concentrations and
sparse populations of zooplankton, introduced fish in the
lake are large in size and in good condition when compared
to fish from other lakes. Fish were originally stocked in
Waldo Lake in the late 1800's. The Oregon Department of
Fish and Wildlife began stocking in the late 1930's and
continued stocking until 1991. Species existing in Waldo
Lake today include brook trout, rainbow trout, and kokanee
salmon.
The overall objective of this thesis was to increase
the understanding of the interrelationships that affect
the age, growth, and diet of fish in Waldo Lake. The
specific objectives were to summarize and synthesize
available information on the substrate, climate, water,
and biota of the Waldo Lake Basin; describe the cultural
history and current cultural values of the Waldo Lake
Basin; determine the age, growth, length, weight,
condition, diet, and reproduction of introduced fish
species in Waldo Lake; interrelate the above information
to show how these components of the natural-cultural
system are related.
Fish were collected one week per month from early
June through mid-October in 1992 and 1993. Variable mesh
experimental gillnets set in nearshore areas were used to
capture fish in 1992. During the 1993 sampling period,
experimental gillnets and trapnets were set in the
nearshore areas of the lake.
Relative age specific growth rates of brook trout in
Waldo Lake are comparable to brook trout growth rates in
other lakes. Brook trout growth rates generally decreased
with age, however, there were no significant differences
in the growth rate of each age class between 1991 and
1993.
The condition of brook trout in Waldo Lake is also
comparable to brook trout in other lakes. The same is
true for rainbow trout and kokanee salmon.
Fish in Waldo Lake are large in size and in good
condition due, in part, to the availability of benthic
macroinvertebrates. Taxa found in stomach contents of
fish captured in Waldo Lake consisted primarily of aquatic
benthic macroinvertebrates, but terrestrial vertebrates
and vertebrates, although infrequently consumed, were also
part of the total diet. Rainbow trout in Waldo Lake
consumed primarily chironomidae larvae and pupae although
odonata larvae, ephemeroptera larvae, and amphipods were
also consumed. Kokanee salmon fed almost exclusively on
chironomid larvae although small numbers of ephemeroptera
larvae, odonata larvae, and coleoptera were also consumed.
The most important macroinvertebrate taxon consumed by
Waldo Lake brook trout was chironomid larvae and pupae,
although other species also were important. The diet of
Waldo Lake brook trout varied in a complex way that
appeared to be related to the relative abundance of
macroinvertebrate taxa, feeding location in the lake, and
time of year. Brook trout diet also varied by size class.
The components of the Waldo Lake natural-cultural
system are complexly interrelated and the nature of these
relationships are constantly changing. Each component in
some way affects and is, in turn, affected by each of the
other components. Changes in some components, such as
substrate, affect other components along geologic time
scales. Other components, such human culture and biota,
may change rapidly within a decade. The capacity of
natural-cultural systems, such as Waldo Lake, to change
over time makes it possible to view the present state of
the system only as a snapshot in time. This dynamic
nature of the Waldo Lake natural-cultural system is not
unique to Waldo Lake, but is expressed in all natural-
cultural systems. / Graduation date: 1997
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/34224 |
| Date | 24 June 1996 |
| Creators | Swets, Nicola L. |
| Contributors | Liss, William J. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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