Coastal cutthroat trout (O. clarki clarki) rear in small, headwater streams
that may be particularly susceptible to impacts from land-use activities such as
logging. Headwater populations of coastal cutthroat trout were trapped from 1997
to 2002 to investigate: (i) the effects of second-growth logging on trout densities
and summer body condition over summer and winter months; (ii) the influence of
physical habitat characteristics on summer trout densities; and (iii) the
characteristics of winter trout movement within different habitat conditions.
Trout mean summer densities in logged streams showed no decline following
harvest, nor were there any large changes evident to physical habitat. However,
among years, mean summer trout densities were higher in streams with deeper
pools. Though summer trout densities remained unchanged in logged streams,
trout densities in control streams declined. This suggests that trout may actually
have benefited from logging, potentially due to enhanced levels of primary
productivity arising from the removal of riparian canopy. Winter trout densities
were similar to summer values, indicating that these headwater streams provided
suitable conditions for trout populations year-round. Low flows during late
summer, which reduce pool depth, may be more limiting to age 1 and older
cutthroat trout found in coastal headwater streams than winter high-flow events.
Increases in stream temperatures following logging activities were not associated
with enhanced summer body conditions of trout, largely because minor
temperature effects of logging (average increases of 1-2° C) were offset by a
colder-than-average post-logging period. Winter movement (average 2-7 habitat units or 21-40 m) was found to be a common behaviour of coastal cutthroat trout
in headwater streams and did not seem to be mediated by dominance hierarchies,
influenced by riparian forest condition, or confer a growth advantage/
disadvantage for trout. Winter movement, however, was somewhat limited and
may be a reflection of the need for trout to seek deeper pool habitats that provide
cover and refuge from high-discharge events. Land-use management practices
that protect existing pools and facilitate the processes that create pools may ensure
the continued persistence of coastal cutthroat trout populations in headwater
streams of southwestern British Columbia.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/15505 |
| Date | 05 1900 |
| Creators | De Groot, Jennifer D. |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Relation | UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/] |
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