Hatchery-reared salmonid fish routinely encounter stress due to handling, barging, tagging, and overcrowding. It has been demonstrated that there exists a direct correlation between stress and transient immune suppression which can last for many days in fish. Epizootic viral infections routinely appear in hatcheries and can have a devastating effect on the fish population. The major viral pathogens in salmon and trout are the fish rhabdovirus, infectious hematopoietic necrosis virus (IHNV), and the fish birnavirus, infectious pancreatic necrosis virus (IPNV). Vaccines for these viral pathogens are under investigation; however, the fish immune system becomes virtually nonresponsive during episodes of immune suppression. It was necessary to develop a nonantibody mediated, nonimmune method for preventing viral infections. An interferon-like substance has been described for fish which possesses antiviral activity against both IHNV and IPNV. Since interferon administered to cattle has been very effective against vesicular stomatitis virus, a cattle rhabdovirus, an examination of interferon-like activity in fish was initiated. We report here the establishment of in vitro interferon assays. In addition, the salmonid genome contains a multigene family of p-interferon-like genes, much like those in the bovine, equine and porcine genome. The rainbow trout interferon-like genes were found to be inducible in a manner which parallels those seen with bovine and human interferons. In addition to the multigene interferon-like family, it was found that rainbow trout also contain a retroposon multigene family. Retroposons are repetitive elements which appear to have arisen by a reverse transcription event. Two Ll like repetitive elements have been cloned, one of which contains a Drosophila retroposon polymerase sequences never before described for salmonid fish. A number of retroviruses have been described in fish including the walleye dermal sarcoma virus and the Atlantic salmon swimbladder sarcoma virus. Interferon shows prophylactic promise both in vivo and in vitro, against the human retrovirus, HIV. Therefore, research into fish interferon may be even more important if it demonstrates not only anti- IHNV and anti-IPNV, but also anti-fish retrovirus properties. / Graduation date: 1993

Thesis (M.S.)--Humboldt State University, 2008. / Includes bibliographical references (leaves 66-69). Also available via Humboldt Digital Scholar.

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [136]-147).

The timing of seasonal events in salmonids is thought to be controlled by endogenous circannual rhythm(s) which are entrained by the seasonally-changing daylength. This thesis investigates the role of the pineal gland in the perception of the photoperiodic zeitgeber and the subsequent transmission of this information to the brain through neural or hormonal pathways. Melatonin biosynthesis by isolated rainbow trout pineal glands was shown to exhibit a differential response to graded photic or thermal stimuli. In vitro experiments were carried out at 10±0.50 C as this provided optimum melatonin levels for radioimmunoassay analysis together with a pineal longevity of up to 14 days. By incorporating a variety of light intensities into the light/dark cycle, the salmonid pineal gland was shown to synthesise significantly different levels of melatonin even when light levels varied by only 0.5 lux. Early work on the salmonid pineal suggested it was unresponsive to red light, having a spectral sensitivity which peaks between 500 and 550 nm, this study has revealed that the pineal is also capable of responding to wavelengths between 660 to 800 nm, at which pineal reception was previously thought to be severely limited. No endogenous rhythm of melatonin secretion was observed within the isolated rainbow' trout pineal gland. Both Atlantic salmon and Atlantic halibut pineals exhibited elevated levels- of melatonin in response to the dark phase, however, they also appeared capable of maintaining this rhythm in the absence of external stimuli. This provides the first evidence that the daily rhythm of melatonin production in these species is controlled by an endogenous circadian oscillator located within the pineal II gland. The pinealectomy technique developed during the course of this thesis successfully abolished the diel rhythm of melatonin secretion and, together with an enucleation procedure, enabled the pineal to be identified as the predominant source of the dark phase melatonin in Atlantic salmon and rainbow trout. However, the lateral eyes did contribute significantly to plasma melatonin levels in both species. Long term experiments, involving pinealectomy and/or implantation of melatonin, were used to investigate the role of the pineal gland in the timing of rainbow trout maturation and smoltification in Atlantic salmon. Pineal removal at the summer or winter solstices did not significantly alter the timing of smoltification. However, significantly higher blood serum osmolarities following seawater challenge tests were observed in smolts implanted with melatonin. This, together with a significant growth increase shown by salmon parr within 1 month of implantation, indicates that melatonin may directly affect the development of salmonids through either a physiological response or by influencing the entrainment of endogenous rhythms. The increased growth observed in the implanted parr is also thought to be responsible for the unimodal population distribution and high percentage of S1 smolts within this group. Investigations into the role of the pineal gland in the timing of spawning in rainbow trout found that pineal removal at the summer solstice caused a 6 week delay in spawning time compared to intact fish. However, no clear effects on spawning time were observed when pineal removal, with or without melatonin implantation, was performed to coincide with the change from long to short daylengths which is known to advance spawning times. Although no significant effect in spawning times was observed between groups, the 4 month spawning period of the pinealectomised group compared to 1 month in the shampinealectomised fish also suggested that pineal removal may have caused a desynchronisation in spawning time. Pinealectomy and/or implantation did not alter egg size or fecundity, but plasma calcium levels were shown to be significantly lower in the pinealectomised trout over the spawning period. To summarise, the pineal gland and melatonin play a significant role in salmonid development. It is suggested that melatonin can influence biological systems through a direct physiological action while the pineal gland may synchronise circannual events through the photoneuroendocrine transduction of seasonal environmental information.

Prior to 1989 the total number of Gyrodactylus species recorded for all British freshwater fish numbered 20. The fauna present on the British Salmonidae was poorly documented and frequently not identified to species level. The European free market, created in 1992, resulted in legislative changes allowing the movement of live fish stocks, albeit under strict disease monitoring conditions, into the UK. One stipulation maintains that the fish stock be free of the ectoparasitic monogenean Gyrodactylus salaris Malmberg, 1957, a parasite made notifiable in the UK in 1987 (Diseases of Fish Act, 1937) owing to its pathogenicity and damage to Norwegian salmon populations in 38 rivers. Although this parasite has been reported since 1957 throughout mainland Europe, its occurrence in the UK was unknown. This project set out to make a national survey of British salmon ids and investigated 250 sample sites, examined four salmonid hosts, Atlantic salmon Salmo safar, brown trout Salmo trutta, rainbow trout Oncorhynchus mykiss and Arctic charr Salvelinus alpinus. Seventy of the sites were found to be positive for Gyrodactylus. Distinctions were made between wild and farmed fish and prevalence, abundance and intensity data collected for comparison. Species determination within the genus Gyrodactylus is based upon subtle differences in hook morphology and has long posed a taxonomic problem. The discrimination of collected specimens was based on two platforms. The initial approach used classical morphometrics from the light microscope, the results being processed using multivariate analyses to separate species. The second approach analysed morphometric data collected from scanning electron micrographs. This was made possible by the development of a sclerite release technique utilising a source of ultrasound to liberate hooks from surrounding tissue and a subsequent flotation stage which permitted flat preparations. Sonication of fresh and frozen material retained the structures that would be lost by enzymatic digestion. The description of new morphometric parameters using digital image analysis allowed the subtle differences in hamuli and marginal hook shape to be discriminated when analysed using principal components analysis (PCA). Four species were identified following multivariate and morphological analyses of opisthaptoral sclerites. G. truttae Glaser, 1975 was found to occur on S. trutta and G. derjav;ni Mikailov, 1975 was found to occur on S. trllfta, S. salar and O. mykiss. Two hitheno undescribed forms, one on S. salar and one on S. alpinus which may be a new species are desclibed. In addition, two forms of G. derjavilli from S. salar and S. alpinlls and one form of G. truttae from S. tnltta are described. Sub-populations of Gyrodactylus sp. were found to be determined by the pattern of distribution of the host; S. salar. The two sub-populations were divided into a southern celtic population (Morph 1) and a nonhern boreal population (Morph 2). Water temperature, was found to be an important environmental parameter influencing sclerite size. The principal component analyses identified key characters which could discriminate G. salaris from the native British species using novel parameters based upon both single elements and the full complement of sclerites. Of these new parameters, the hamulus angle and the size of the marginal hook sickle aperture were the most discriminating. Electronmicrographs of hamuli were traced using a digitising tablet and prepared for image processing. The hamulus angle was measured on original hook images and on enhanced (skeletonised) images using an image analyser. Skeletonisation investigated the reliability of the hook angle as a taxonomic criterion by the removal of possible age-related sclerotisation of the hamulus. Statistical analysis of the data revealed that there are significant differences in hook angle between some species. The isolation of sclerites by sonication enabled their elemental composition to be investigated. The hamuli and marginal hooks were found to have a high sulphur content, indicative of a keratin-like substance. The ventral bar composed of sulphur and calcium is weakly keratinised. The hamulus and the ventral bar were also found to contain vanadium. the significance of which is unknown. The detailed morphology and composition of the individual sclerites is discussed in relation to the functional mechanics of the entire haptoral complex. The protein profiles of G. salaris. G. truttae and G. derjvani were investigated using SDS-PAGE gel electrophoresis, with four proteins common to the three species. Two antibodies raised against G. salaris were found using Western blots. The chaetotaxy of argentophilic structures on three species of the genus Gyrodactyllis was investigated to ascertain the usefulness of this technique in distinguishing species of this genus. Chaetotaxy maps were prepared for G. salaris from Scandinavia and compared to native species of Gyrodactylus parasitizing salmonids in Britain. A formula for the arrangement of the sensilla analogues and the evolutionary position of the genus Gyrodactylus is commented upon.

Juvenile coho, steelhead, and cutthroat trout commonly spend from one to three or more years in coastal streams before migrating to the sea. Much of this time is spent in streams during the winter, making a study of these fishes' winter habitat requirements, distribution, behavior, and the possible influences of stream habitat alteration on them a useful undertaking. Some physical characteristics of areas selected by juvenile coho and steelhead were observed by snorkeling in a small west coast of Vancouver Island stream between September 1972 and April 1973. Observations revealed that with lowering water temperatures from 9°C to 2°C coho and older steelhead tended to move into deeper water while most steelhead fry remained in shallow, marginal sections of the stream. As water temperatures dropped in the winter, juvenile fish fed less and moved closer to areas offering low water velocities and cover. Steelhead fry were most often found under rubble while coho and older steelhead were most often found within upturned roots and under logs. Results from fish traps located on the lower ends of two small tributary streams indicated that juvenile coho, steelhead and cutthroat trout moved upstream into these tributaries in the late fall. Overwinter survival of coho in one tributary was 3-6 times as great as the estimated survival of coho in the main stream. Together the two tributaries contributed between 15 and 25 per cent to the total coho smolt production of the larger system. A series of experiments comparing coho and cutthroat preference for alternative habitat types in sidepool areas as may occur before and after stream disturbance were carried out during the winter. Both coho and cutthroat demonstrated a strong preference for bay areas offering overhanging bank cover as opposed to bays without cover, and for bays offering clean rubble substrate as opposed to silted rubble substrate. The impacts of timber harvesting on overwintering fish as suggested by the results from the underwater observations, winter movements, and the sidepool experiments are discussed and management recommendations are made. / Forestry, Faculty of / Graduate

The purpose of this work was to determine if environmentally-relevant concentrations of chlorpyrifos and copper, two commonly detected chemicals in Western surface waters, can negatively impact the biological health of salmonids. Both compounds are highly neurotoxic to fish, but each with distinct biological target sites and mechanisms of action. We used common biochemical and physiological indicators of toxicity, and correlated these effects with potentially significant behavioral alterations. For chlorpyrifos, the mechanism of toxic action is the inhibition of acetylcholinesterase (AChE) throughout the peripheral and central nervous system. Here, we conducted biochemical assays of AChE activity in brain and muscle tissues after exposing steelhead trout (Oncorhynchus mykiss) and coho salmon (0. kisutch) to chlorpyrifos for 96 hours. We then correlated the AChE inhibition with behavioral impairment in swimming and feeding activities. In juvenile steelhead and coho exposed to 0.6-2.5 ��g/L chlorpyrifos, AChE activity was inhibited between ~10-65%. This biochemical indicator was significantly correlated with changes in behavioral patterns. Spontaneous swimming rates were reduced ~30-80% in the exposed fish, and strikes at food items (brine shrimp) were reduced ~10-70%. For copper and some other neurotoxicants, the olfactory nervous system is a sensitive target site in fish. The highly-developed olfactory system in salmonids is particularly susceptible to toxic insult by dissolved chemicals since receptor neurons are in direct contact with the aquatic environment. Here, we used electrophysiological techniques to record odor-evoked responses from the sensory epithelium and the olfactory bulb as direct measures of olfactory function in juvenile coho salmon. In fish exposed to copper, chlorpyrifos, or esfenvalerate for 7 days, field potentials recorded from the sensory epithelium and the olfactory bulb showed reduced or obscured olfactory responses to two classes of odorants, which activate non-overlapping populations of receptor neurons. To determine if this reduced sensory input can subsequently alter or diminish olfactory-mediated predator avoidance behaviors, paired physiological and behavioral tests were conducted on juvenile coho exposed to copper. In fish exposed to 2-20 ��g/L copper for 3 hours, olfactory sensitivity was reduced by ~50-9O%. When these fish were presented with a predatory alarm cue (conspecific skin extract), fish with reduced olfactory function increasingly failed to exhibit antipredator behavior. In the following experiments, we show that chlorpyrifos and copper can impair the biochemical and physiological biology of salmonids at environmentally-relevant concentrations, and that these sublethal effects can alter potentially important behavioral patterns. / Graduation date: 2004

Graduation date: 1991

Thesis (M.E.S.)--The Evergreen State College, 2001. / Title from title screen viewed (3/20/2008). Includes bibliographical references (leaves 41-44).

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 46-51). Also available on the World Wide Web.