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UBC Theses and Dissertations
Responses of sockeye salmon (Oncorhynchus nerka) embryos to intragravel incubation environments in selected streams within the Stuart - Takla watershed Cope, R. Scott
Abstract
Before impacts of forest harvesting can be identified, the natural physical and biological influences on incubation processes must be understood within interior British Columbia watersheds. The early Stuart stock of sockeye salmon {Oncorhynchus nerka) utilize the most northerly nursery habitat of the Fraser River sockeye stocks. This has led to speculation that production may be limited by high overwinter incubation mortality. An in situ incubation study was conducted on four adjacent tributaries of the Stuart Takla watershed (Kynock, Forfar, Gluskie, Bivouac creeks), during the 1993 and 1994 broodyears. The study objective was to estimate overwinter survival of sockeye salmon embryos within various redd micro-environments. It was hypothesized that spawning salmon select incubation sites based on environmental cues to optimize egg to fry survival. Egg to pre-emergent , fry bioassays, in conjunction with microhabitat environmental monitoring, were implemented to define a range of natural spawning conditions and their relative contribution to fry recruitment. Results demonstrate that high quality, relatively invariant incubation environment resulted in the lack of classical relations observed in previous studies between incubation parameters and survival.. Physical processes (i.e. hydraulic regime, bedload characteristics) and biological processes (i.e. mass cleaning by high densities of spawning adults) result in uniformly high quality gravel conditions with permeabilities, surface water interchange, and intragravel dissolved oxygen levels associated with high incubation success. Alternative hypotheses of random egg deposition and unlimited high quality habitat were rejected due to; 1) observed spatial preferences and, 2) expansion/contraction of range under different annual population sizes. Sockeye salmon successfully spawned over a wide range of habitats. High density spawning habitat was the downstream end of pools at the pool riffle interface. Habitats utilized to a lesser degree included; riffles, stream margins, intermittent side channels and portions of the off-channel habitat. Survival rates between these habitat types were not significantly different in contrast to predictions generated from optimality models. This was due to the definition of "marginal" habitat. In situ redd simulations showed similar intragravel conditions, in both low density (i.e. assumed marginal) and high density (i.e. assumed preferred) areas. Spawning adults avoided truly marginal areas with intragravel dissolved oxygen levels below 3.0 mg/1. A number of adaptations which would optimize incubation success in northern environments were identified within the early Stuart stock of sockeye salmon. Early Stuart sockeye risk energy depletion and seasonal maximum temperatures during migration and spawning. By spawning early in the season (Jul. - Aug.), early Stuart sockeye enjoy advanced embryological development prior to the onset of low water temperatures. Embryos rapidly accumulate the thermal units necessary to hatch, thereby becoming mobile in time to avoid freezing and desiccation as water-levels decline and reach seasonal minima. Embryos and alevins of the early Stuart stock can apparently tolerate temperature conditions previously considered lethal. Fry successfully emerge in the spring after accumulating less thermal units than any other Fraser river stock. The trade off against this strategy is the effect of unusually stressful migration conditions on the quality and viability of the gametes. Evidence of this trade off was obtained in 1994, when egg survival rates were very low for spawners that arrived late and had suffered severe thermal stress during migration.
Item Metadata
Title |
Responses of sockeye salmon (Oncorhynchus nerka) embryos to intragravel incubation environments in selected streams within the Stuart - Takla watershed
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1996
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Description |
Before impacts of forest harvesting can be identified, the
natural physical and biological influences on incubation processes
must be understood within interior British Columbia watersheds. The
early Stuart stock of sockeye salmon {Oncorhynchus nerka) utilize
the most northerly nursery habitat of the Fraser River sockeye
stocks. This has led to speculation that production may be limited
by high overwinter incubation mortality. An in situ incubation
study was conducted on four adjacent tributaries of the Stuart Takla
watershed (Kynock, Forfar, Gluskie, Bivouac creeks), during
the 1993 and 1994 broodyears.
The study objective was to estimate overwinter survival of
sockeye salmon embryos within various redd micro-environments. It
was hypothesized that spawning salmon select incubation sites based
on environmental cues to optimize egg to fry survival. Egg to
pre-emergent , fry bioassays, in conjunction with microhabitat
environmental monitoring, were implemented to define a range of
natural spawning conditions and their relative contribution to fry
recruitment.
Results demonstrate that high quality, relatively invariant
incubation environment resulted in the lack of classical relations
observed in previous studies between incubation parameters and
survival.. Physical processes (i.e. hydraulic regime, bedload
characteristics) and biological processes (i.e. mass cleaning by
high densities of spawning adults) result in uniformly high quality
gravel conditions with permeabilities, surface water interchange,
and intragravel dissolved oxygen levels associated with high
incubation success. Alternative hypotheses of random egg deposition
and unlimited high quality habitat were rejected due to;
1) observed spatial preferences and, 2) expansion/contraction of
range under different annual population sizes.
Sockeye salmon successfully spawned over a wide range of
habitats. High density spawning habitat was the downstream end of
pools at the pool riffle interface. Habitats utilized to a lesser
degree included; riffles, stream margins, intermittent side
channels and portions of the off-channel habitat. Survival rates
between these habitat types were not significantly different in
contrast to predictions generated from optimality models. This was
due to the definition of "marginal" habitat. In situ redd
simulations showed similar intragravel conditions, in both low
density (i.e. assumed marginal) and high density (i.e. assumed
preferred) areas. Spawning adults avoided truly marginal areas with
intragravel dissolved oxygen levels below 3.0 mg/1.
A number of adaptations which would optimize incubation
success in northern environments were identified within the early
Stuart stock of sockeye salmon. Early Stuart sockeye risk energy
depletion and seasonal maximum temperatures during migration and
spawning. By spawning early in the season (Jul. - Aug.), early
Stuart sockeye enjoy advanced embryological development prior to
the onset of low water temperatures. Embryos rapidly accumulate the
thermal units necessary to hatch, thereby becoming mobile in time
to avoid freezing and desiccation as water-levels decline and reach
seasonal minima. Embryos and alevins of the early Stuart stock can
apparently tolerate temperature conditions previously considered
lethal. Fry successfully emerge in the spring after accumulating
less thermal units than any other Fraser river stock. The trade off
against this strategy is the effect of unusually stressful
migration conditions on the quality and viability of the gametes.
Evidence of this trade off was obtained in 1994, when egg survival
rates were very low for spawners that arrived late and had suffered
severe thermal stress during migration.
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Extent |
8013025 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-02-11
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0074813
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1996-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.