I investigated juvenile coho salmon (Oncorhynchus kisutch) distribution and
habitat utilization in an agricultural/urban watershed, the Salmon River, Langley, B.C.
The results of my empirical work confirmed the importance of instream woody debris and
undercut banks in coho distribution. I examined experimentally how juvenile coho select
among patches that differ in foraging profitability and in cover availability. Ideal free
distribution (IFD) models were used as the practical basis for hypotheses about habitat
choice by coho salmon. My experiments were conducted in artificial stream channels and
involved two different types of cover, instream and overhead, and two spatial scales. The
two scales (patches within individual pools and pools within stream reaches) were used to
detect the effect of different levels of sampling and information processing by the fish.
Juvenile coho responded positively to food abundance both within and between pools, but
they did not do it as predicted by the IFD model. Cover presence further deviated coho
distribution from an IFD. Within pools, coho foraged in open patches away from cover,
but preferred pools with cover when choosing between separate units. None of the
alternative dispersion models that I considered, derived from the IFD, fully explained the
observed dispersion patterns. Coho's ability to maximize food intake rate was not only
affected by the physical complexity of their habitat, but also by intraspecific competition
and interference. Subsequently, I investigated experimentally coho's response to food and
different densities of woody debris in natural stream reaches. If food was abundant, coho
favoured pools with sparse cover, which offers accessible refuge and leaves unobstructed
foraging patches where prey and perhaps also predators are easy to detect. Pools with
either high densities or total lack of woody debris attracted proportionately less fish.
Earlier in the summer, fry were indifferent towards cover, but as they became older their
association with instream woody debris increased. Experiments I conducted during
winter indicated that water velocity and temperature affected juvenile coho downstream movement. The proportion of fish that tried to leave the experimental channels increased
with water discharge and decreased with water temperature.
Based on the results of my empirical and experimental work, and on information
derived from comparative case studies, I evaluated the potential impact of agriculture and
urbanization on coho salmon habitat. Activities associated with these types of land
developments tend to: a) reduce stream channel complexity; b) eliminate off-channel
fish habitat; c) increase both the magnitude and the frequency of peak flows; d)
augment water sediment transport; e) alter riparian vegetation; and, f) degrade water
quality.
A multilayered management plan, aimed at increasing coho salmon production,
was developed. The plan's management strategies were devised reflecting on the different spatial scales that watershed components have and on the connectivity processes that exist
among them.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/4755 |
| Date | 05 1900 |
| Creators | Giannico, Guillermo Roberto |
| 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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