Many economically important Pacific salmon fisheries along the west coast of North America are mixed-stock, recreational systems, in which managers strive to account for interactions between fish, anglers, and management policy while balancing fishery access against conservation of vulnerable stocks. Specific challenges facing fisheries managers include limited control over angling...
Juvenile Chinook Salmon (Oncorhynchus tshawytscha) have a finite amount of energy that they can use to move from their riverine habitat to their oceanic habitat. Fish in the Willamette River Basin are prevented from moving to the ocean easily by dams which create reservoirs, where they reside for up to...
More than 1500 species of plants and animals in the United States are listed as threatened or endangered under the Endangered Species Act (ESA). The U.S. Departments of Interior and Commerce are required, under Section 4(f)(1) of the ESA, to develop recovery plans for ESA-listed species under the respective agency...
Juvenile Chinook salmon (Oncorhynchus tshawytscha) exhibit an array of life history tactics in Oregon's Willamette River Basin, yet we do not know to what extent it is driven by phenotypic plasticity or whether it is predetermined and how conditions in the early rearing environment may affect phenotype expression. We have...
Pacific lamprey Entosphenus tridentatus is a valuable icon and traditional food source for Indigenous people of western North America. Native Americans have utilized traditional ecological knowledge (TEK) since time immemorial to guide their ways of life, transmitting cultural values and natural history to further generational knowledge. Pacific lamprey are in...
Rainbow trout (Oncorhynchus mykiss) experience a variety of stressors in their natural environment as well as in aquaculture that can have negative effects on their physiology. The effects of physiological stress and endocrine disruption have been well described in fish. However, there is a scarcity of information on the effects...
Spring Chinook salmon, Oncorhynchus tshawytscha, are transported above dams in the Willamette River to provide access to blocked spawning habitat. However, 30-95% of these transplants may die before spawning in some years. To varying degrees, salmon in other tributaries--both blocked and unblocked--have similar prespawn mortality (PSM). Our study determined if...
Juvenile coho salmon (Oncorhynchus kisutch) of three transferrin
genotypes (AA, AC and CC) were experimentally infected with the
causative agent of bacterial kidney disease (BKD) and mortalities
observed. Six experimental and control groups were used:
(1) bacteria-infected + no Fe⁺³ ; (2) bacteria-infected + low Fe⁺³
levels; (3) bacteria-infected +...
Juvenile coho salmon (Oncorhynchus kisutch) and steelhead trout
(Salmo gairdneri) of different stocks and three transferrin genotypes
(AA, AC, and CC), all reared in identical or similar environments, were
experimentally infected with the causative agent of bacterial kidney
disease (BKD) or Vibrio anguillarum. Mortality due to the pathogens
was compared...
Coho salmon smolts (Oncorhynchus kisutch) were transported at low and high densities. (12 and 120 g/L) for short and long periods (4 and 12 h). Because smolts can be transplanted directly to seawater, half of the fish in each treatment were transported to tanks containing seawater and half to tanks...
Chinook salmon, Oncorhynchus tshawytscha, returning to the Yukon River basin and other large river systems in western Alaska have declined dramatically since the late 1990s. This continuing trend has raised concerns over the future status of the returns, and severely impacted commercial and subsistence fisheries within the drainage. Management is...
Plasma concentrations of cortisol, a glucocorticoid hormone that
is immunosuppressive in mammals, increase during stress and
smoltification of salmonids. There was a reduction in the ability of
lymphocytes to generate antibody producing cells (APC) in vivo
concurrent with increased plasma cortisol titers during smoltification
of coho salmon (Oncorhvnchus kisutch). Cortisol...
Reproduction of salmonid fishes in acidic water was studied
using the rainbow trout (Salmo gairdneri). Adult trout were exposed
to various levels of hydrogen ion (pH levels 4.5, 5.0, 5.5, and
control [6.5 to 7.1]) during the final 6 weeks of reproductive
maturation. Reduced survival rates of the progeny of...
Whole body sex steroid levels of coho salmon,
Oncorhynchus kisutch, were measured via radioimmunoassay
during early development and sexual differentiation.
Steroid profiles of testosterone (T), 11-ketotestosterone
(KT) , androstenedione (A), progesterone (P4) , 17β, -hydroxy-
20β -dihydroprogesterone (DHP) , and 17β -estradiol (E2) were
generated beginning with unfertilized eggs and...
We examined the behavioral and physiological responses of wild
and hatchery-reared cutthroat trout Oncorhynchus clarki subjected to
a single electroshock, electroshock plus marking, and multiple
electroshocking in natural and artificial streams. In a natural
stream, trout released after capture by electrofishing and marking
showed distinct behavioral changes: fish immediately sought...
Although differences between selective pressures in hatcheries
and streams have been theorized to cause genetic divergence between
hatchery and wild salmonids, evidence of this is lacking. This study
was initiated to document the presence or absence of genetic change
in hatchery and wild stocks by characterizing genetic traits in fish...
Sexual maturation and sex differentiation comprise facets of a
common theme: reproduction. The endocrine system regulates many
of the critical physiological processes necessary for reproduction and
offers a framework within which technologies can be developed for
controlling sexual maturation and sex differentiation. The studies
described in this thesis were undertaken...
Various aspects of the energetic response to handling stress in juvenile
coho salmon (Oncorhynchus kisutch) were examined. Fish were subjected to
four different handling stressors in a Blazka-style respirometer. Stressed fish
had rates of oxygen consumption that were higher than controls. The
magnitude of the increase ranged from 139 to...