Ecological studies
frequently focus on the relationships between animal distributions
and physical environmental factors. In stream ecology, physical
factors are often viewed as the primary regulator of aquatic
animal distributions. As a result, the highly uneven and patchy
distribution patterns exhibited by stream fishes are attributed
to the heterogeneous and variable nature of stream habitat.
Even so, ecologists have had a difficult time developing models
that accurately predict standing crops of stream fishes from
physical habitat variables. A lack of appreciation for the spatial
organization of stream habitat and a failure to understand the
behavioral responses of fishes to stream habitat may be responsible
for these poor results. More recently, ecologists have begun
to recognize that the spatial structure of stream habitat and
the ability of fish to disperse among these habitats can have
a strong influence on the abundance and distribution of fish.
Conceptual models that link stream spatial structure, fish dispersal,
and fish population dynamics have been proposed, but few studies
have directly addressed these relationships.
Understanding the interactions between lotic habitat and fish
behavior may be particularly important for the management and
conservation of coastal cutthroat trout (Oncorhynchus clarki
clarki). Coastal cutthroat trout populations are in decline
throughout the region, and aquatic habitat
degradation resulting from land-use activities has been identified
as a potential cause for this decline. First- and second-order
streams are readily impacted by upslope land uses, and as a
result, headwater populations of coastal cutthroat trout may
be even more vulnerable to anthropogenic influences. Identifying
the relationships between stream habitat and coastal cutthroat
trout dispersal is vital for understanding coastal cutthroat
trout population responses to human induced habitat alterations
in headwater streams. Despite the importance of dispersal in
trout population dynamics, significant questions remain unresolved:
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How do stream habitat
variables impact the dispersal of coastal cutthroat trout?
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How
does stream habitat and trout dispersal interact to influence
trout abundance and distribution? |
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To examine these questions, we will characterize the distribution
of related coastal cutthroat trout in a headwater stream.
If dispersal only occurs on small spatial scales, large numbers
of related individuals will exhibit highly clumped distributions.
In contrast, if trout are dispersing widely, related individuals
will be distributed extensively through the stream network.
Specific objectives of this study include comparing genetic
distribution patterns within and among different geomorphic
reach types and associating particular habitat variables with
trout dispersal. In addition, we will examine patterns in
trout abundance and explore the associations between trout
dispersal and trout population dynamics.
For additional information about this completed study see
the 2003 CFER
Annual Report. (2.2 MB)
