Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 150-162).

An integrated laboratory and field approach was used to study the behaviour and ecology of Pacific salmon (genus Oncorhynchus) alevins in the gravel. The hypothesis tested was that these yolk sac fry move throughout the gravel prior to emergence, that this movement has both lateral and vertical components, and that changes in the physical or biological environment will alter certain parameters of subgravel behaviour. Eyed chum salmon (0. keta) eggs were buried in incubation channels at Robertson Creek, B. C. Eight experimental treatments were chosen, utilizing two gravel sizes, two burial depths and two planting densities. The fry were captured at emergence by means of specially designed traps that allowed determination of degree of lateral movement, pattern of emergence and survival to emergence. The fry were also sampled for condition (weight-length ratio) at the time of emergence. In the larger gravel, survival was greater, lateral movement was increased, and initial emergence was earlier. At the greater burial depth the emergence period was longer. At the greater burial density initial emergence was earlier. Condition at emergence was the same in all treatments. The behaviour of coho salmon (0. kisutch) alevins was examined in specially constructed aquaria, where light and flow conditions were as natural as possible. The same environmental factors were varied as in the field. In addition to a general description of alevin behaviour, detailed analyses were carried out on: vertical and lateral movement, orientation, spatial distribution, condition, survival and pattern of emergence. In the larger gravel vertical and lateral movements were increased, survival was higher, area utilization was greater and condition at emergence was poorer. At the greater burial depth lateral movement towards the outlet was increased and initial emergence was earlier. Vertical movement was decreased because more fry were trapped within the gravel. At the higher density the alevins moved farther towards the inlet. The mean area occupied per alevin was unchanged by density and suggests competition within the gravel. The orientation of the alevins is discussed in relation to light and current. The results indicate that larger gravel is better than smaller gravel for the incubation of Pacific salmon. Burial depth seems unimportant, but should be great enough to prevent predation. The question of optimum density requires further study. Emergence patterns may apparently be modified through environmental control. / Science, Faculty of / Zoology, Department of / Graduate

The possible role of prolactin in the freshwater osmoregulation of laboratory reared juvenile chum (Oncorhynchus keta) and sockeye (0. nerka) salmon was investigated. Pituitary cytology indicated that prolactin cells of both species develop gradually during freshwater residence and downstream migration. During this time the prolactin cells increase slightly in size; the number of prolactin cell follicles also increases. Simultaneously, the intensity of cytoplasmic staining with erythrosin increases. Alternate day injections of 5 or 15 μg/g body wt prolactin (ovine) did not affect survival of chum fry in deionized water. Thirty micrograms per gram slightly increased survival while 60 μg/g decreased survival in deionized water. Prolactin injections prolonged, to a small extent, the survival of sockeye smolts in deionized water. Sockeye fry suffered only slight mortality after transfer from fresh water to deionized water. A prolactin dose of 5 μg/g did not alter this survival; however, doses of 15 μg/g or higher resulted in 40 to 70% mortality after 10 days in deionized water. Alternate day injections of 10 μg/g prolactin had no effect on plasma sodium concentrations of chum fry, sockeye fry, or sockeye smolts after transfer from sea water to either fresh water or deionized water. It is concluded, from histological and physiological evidence, that prolactin does not play an obvious role in the freshwater osmoregulation of juvenile chum and sockeye salmon. The possible role of prolactin in the spawning migration of adults is discussed. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (Ph. D.)--Oregon State University, 2001. / Typescript (photocopy). Includes bibliographical references (leaves 334-368). Also available via the World Wide Web.

The main parasite affecting the Scottish Atlantic salmon farming industry is Lepeophtheirus salmonis costing approximately £29 million annually through lost production and treatments. As such, the primary aim of this study was to investigate the infection pressure, fecundity and infection dynamics of L. salmonis in a west coast sea loch containing salmonid aquaculture. Atlantic salmon held in small sentinel cages were used to monitor sea lice infection pressure in Loch Shieldaig. Investigation of the factors affecting infection pressure within the loch found no evidence of a direct link between monthly gravid lice counts on local farmed salmon and lice burdens on sentinel cage fish. Copepodid L. salmonis were present throughout the year despite there being low numbers of wild salmonids in the system during much of the year and as such the source of this infection was unclear. In subsequent laboratory trials, L. salmonis from wild salmon were found to be more fecund than those from farmed salmon and similarly, fecundity and survival were also higher in summer compared to winter populations of L. salmonis. These findings raise the possibility that L. salmonis infecting wild salmonids may “seed” previously fallowed systems. Alternatively, trials with atypical hosts found that L. salmonis of farmed origin did re-infect Atlantic cod and produce viable egg strings which moulted through to the infective copepodid stage. Infection challenges demonstrated that L. salmonis copepodids were observed to settle on atypical hosts such as saithe and Atlantic cod in low numbers although failed to develop to the chalimus stages and complete its lifecycle. Challenges utilising the mobile pre-adult stage were similarily unsuccesful in allowing L. salmonis to moult to the adult stage on these atypical hosts. Previous work conducted on Pacific three-spined sticklebacks demonstrated the species could support large burdens. In infection trials with three-spined sticklebacks from Scotland’s west coast, settlement was found to be low, which suggests they play no role in the Scottish inshore infection dynamics of L. salmonis. These series of studies provide novel and timely data on the biology and infection dynamics of L. salmonis on typical and atypical hosts in Scottish marine aquaculture areas. The data will form part of the knowledge used to make informed pest management and policy decisions assisting the future development of the aquaculture industry in Scotland.

The present work reports on extensive plankton sampling surveys in a Scottish sea loch used by wild and farmed salmonids and describes the spatial and temporal distribution of planktonic larval sea lice and identifies factors which affect the larval distribution. The planktonic louse larvae recovered were predominantly <i>Lepeophtheirus salmonis</i> (Krøyer) and so the findings of this thesis refer primarily to this species of sea louse. Copepodids occurred in significantly greater densities at 0 m than at a depth of 5 m, whereas nauplii occurred in significantly greater densities at 5 m than at 0 m depth. Densities of caligid nauplii and <i>L. salmonis</i> copepodids recovered from the open-waters of Loch Shieldaig correlated significantly with the counts of gravid <i>L. salmonis</i> on farmed Atlantic salmon at the farm in Loch Shieldaig. Furthermore, the densities of <i>L. salmonis</i> copepodids were significantly correlated  with the estimated total numbers of gravid <i>L. salmonis</i> on all farmed Atlantic salmon in the Loch Torridon management area. Densities of <i>L. salmonis</i> copepodids did not correlate with estimated numbers of gravid <i>L. salmonis</i> on wild salmonids. Atlantic salmon farms were identified as important sources of <i>L. salmonis</i> larvae and these larvae can be transported several kilometres from the point of release. Husbandry louse control practices were indicated to be able to significantly reduce the densities of <i>L. salmonis</i> larvae in the water column. These findings support the principle of synchronised sea louse management at a hydrographic/management area level.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 130-142). Also available on the World Wide Web.

There have been numerous studies in which the reproductive cycles of teleosts have been correlated with either environmental cycles or associated physiological cycles, or both. Such correlation is seldom accurately achieved; usually because the reproductive cycle of the species concerned is lax, sometimes because only one or two factors of an integrated whole were examined. The powan of Loch Lomond, Coregonus lavaretus (L. ) (Teleostei, Salmoniformes) is the subject of a long-term study investigating its growth, in particular reproduction. This race is a freshwater glacial relict form of a boreal group, and thus has an exceptionally strictly times reproductive cycle. It thus represents an ideal subject for cyclical studies. This thesis investigates the relationship between lipid storage and the reproductive cycle and the role of thyroid gland.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 100-108). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 97-105). Also available on the World Wide Web.