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...
Juvenile chinook salmon (Oncorhynchus tshawytscha) were experimentally infected with Renibacterium salmoninarum (Rs), the causative agent of bacterial kidney disease (BKD), to investigate the effects of BKD on three aspects of juvenile salmonid performance: (1) predator avoidance ability; (2) smoltification; and (3) physiological responses to stress. For these experiments, fish with...
Electrofishing is a sampling tool commonly used by fisheries researchers. While much is known about the effects of electroshock on fish physiology, consequences to the immune system and disease progression have not received attention. To understand the effects of electroshock on immune function we undertook a comparison of electroshock 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...
Stress, including extreme or rapidly changing temperatures, are known to have deleterious effects on fish health and physiology. This thesis examines the combined effects of elevated acclimation temperature and acute handling stress on the number of antibody producing cells, plasma lysozyme concentrations, and the number of pronephric leukocytes in juvenile...
Environmental factors such as chemical contamination can have immunomodulatory effects on the immune response of fish and may be contributing to the decline in salmonid populations by augmenting disease susceptibility. Xenobiotics can interfere with the immune system at several levels of complexity, and different immune cells and processes have variable...
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...
Wild populations of fish are faced with a multitude of stressors, which may include human interaction, toxins, and disease. Benzo(a)pyrene (BaP), a known carcinogen and immunotoxin, has been reported in the stomach contents of juvenile chinook salmon, Oncorhynchus tshawytscha, in urban waterways. We investigated the impact of chronic dietary exposure...
Genetic, ontogenetic, and environmental factors modified characteristic interrenal and glycemic responses to stress in juvenile salmonid fishes. During continuous confinement stress, plasma cortisol rose more quickly in chinook salmon, Oncorhynchus tshawytscha, acclimated to high rather than medium or low temperatures; hyperglycemia following either acute or chronic stress was also highest...
Three experiments were designed to determine if and how steelhead trout,
Oncorhynchus mykiss, may affect chinook salmon, O. tshawytscha, when they are
confined together as in a raceway or on a barge. We observed groups of chinook and
steelhead together and groups of only chinook in a behavioral experiment to...
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...
The environment under which fish are maintained as broodstock before
reproduction is often stressful; however, the impact of stress on broodstock and gamete
quality is not well known. We investigated the effects of stress over the final stages (i.e.
the 3 months preceding ovulation) of sexual maturation of female rainbow...
Sablefish, Anoplopoma fimbria, is a valuable North Pacific Ocean species caught in several commercial fisheries and is often discarded due to size or catch limits. Managers must account for the mortality of discarded fish to assess fish populations and harvest impacts, yet discard mortality rates of specific fisheries are generally...
In this thesis, we examined the effects of the exposures to anthropogenic pollutants on the fish, primarily juvenile chinook salmon, immune system using newly and recently developed immune assays. In addition, we developed a new assay for measuring immunocompetence of fish. In the first chapter, the Alamar Blue assay was...
Periodic determinations of plasma hormone levels suggested that changes in interrenal activity are unrelated to changes in thyroidal or gonadal activity during development (smoltification) of juvenile coho salmon (Oncorhynchus kisutch). Moreover, in an experiment where fish were reared under various conditions of crowding and water inflow rate, it appeared that...
Sex steroids, follicle stimulating hormone (FSH),
luteinizing hormone (LH) and gonadotropin releasing hormone
(GnRH) were measured in monosex and mixed sex populations of
rainbow trout during early development. Steroids declined
following fertilization, increased at hatch, then fell and
remained constant thereafter. Trends toward differences in
steroids between males and females...
The extent to which responses to stress are maladaptive or adaptive to the long-term survival of fish remains to be better understood. The aim of this study was to identify differentially expressed genes in the livers of rainbow trout, Oncorhynchus mykiss, responding to an experimental stressor. Gene expression responses were...
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...
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...