Studies were carried out to determine the influence of the change in the acid-base status of the blood on regulation of pH in relation to control of ventilation in the rainbow trout. By placing trout in ventilation (VG) boxes direct measurement of ventilation volume and rate could be made. Arterial blood was collected via chronically implanted catheters in the dorsal aorta; these catheters also allowing administration of the various acids and bases. The first series of experiments were designed to determine ventilatory responses to high ambient PCO₂ levels (hypercapnia) and the effect on regulation of arterial blood pH. Both short-term (up to 8 hours) and long-term (up to 72 hours) exposures were studied. PaO₂ levels remained saturated, or nearly so, throughout these experiments. The general response to high PCO₂ levels is an increase in the ventilatory stroke volume, this being mainly due to an increase in rather than VG. Compensation of ventilation during the sustained hypercapnia is slow, taking up to 3 days. Arterial H⁺ levels increased during CO₂ exposure, increasing from a control level of 11.8 ± 0.5 to 41.0 ± 3.5 nM/L within 5 minutes. There is a gradual decrease in arterial H⁺ concentration such that at 72 hours it is near normal. The time course of compensation for both VG and pHa coincide. The hypercapnia experiments indicate that in the face of an increase in ambient PCO₂ trout do not adjust the PCO₂, difference (ΔPCO₂ between arterial blood and water. PaCO₂ changes in proportion to the change in PICO₂ such that PaCO₂ is always about 2 mm Hg above ambient, demonstrating that ΔPCO₂ is not affected by changes in ventilation. The change in arterial blood pH is shown to be related to the transfer of CO₂ rather than by a transfer of H⁺ ions from water to blood. Arterial blood pH is regulated via adjustment of blood HCO⁻₃ levels, adjustment being in the order of 2 - 3 days. HCO⁻₃ can be regulated, or adjusted by either the kidney or the gills. The role of the kidney was shown to be minor in the adjustment of a NaHCO₃ induced alkalosis. Uptake of HCO⁻₃ is shown to occur when fish are placed in NaHCO₃ containing water, demonstrating the role of the gills in the amelioration of arterial blood pH. These observations are discussed in relation to a HCO⁻₃/Cl⁻ exchange. The ventilation volume is dependent on an increase in PaCO₂ and/or PICO₂ and not to pHa or pHI. A decrease in pHI, although causing a fall in pHa, has only a delayed effect on VG. The response in VG is transient. It is postulated that receptors are either adapting or are not located in the blood or water but in another compartment whose contents or properties change in proportion to ventilation. It is hypothesized that a chemosens.itive area may exist on the ventrolateral surface of the medulla as in mammals. Perfusion of the cranial cavity of trout with mock CSF, in which CO₂-HGO⁻₃ was altered, did not elicit respiratory responses. These experiments do not preclude the existence of medullary chemoreceptors. These results are consistent with the hypothesis that ventilation in trout is dependent on the CO₂ tension within the body or elsewhere and that blood pH levels are regulated via ionic exchange mechanisms at the gill surface, rather than by ion exchange at the kidney or by diffusive washout of gaseous CO₂ via ventilation. / Science, Faculty of / Zoology, Department of / Graduate

The upstream-downstream response to water current exhibited by rainbow trout fry in inlet and outlet streams of Loon and Pennask Lake stream systems was studied in experimental laboratory performance channels. Analysis of diallel tables, developed by crossing seven different inlet and outlet spawning stocks from the two stream systems, demonstrates additive genetic differences between the two stocks with respect to current response. Tests performed in daylight showed a net upstream movement for all stocks, but far greater for outlet compared to inlet fry. At night, inlet fry showed a very strong downstream movement while outlet fry showed very little movement, similar to their behavior in the field. Further analysis of the diallel table, when all the stocks were tested at three temperatures (low: 5C, medium: I0C, high: 17.5C), showed that temperature both in daylight and darkness tended only to change the degree of upstream or downstream movement of the fish, rather than the direction of movement. In daylight, upstream movement for all stocks was greatest at low temperature and least at high temperature. In darkness the greatest downstream response was at high temperature. However, at high temperature outlet fry moved farthest upstream in daylight while in darkness inlet fry moved farthest downstream. Other possible controlling mechanisms (sudden temperature rises in the outlet creek, water source, abundance of food, genetic differences in liver lactate dehydrogenase) are considered. The diallel analysis suggests that there are genetic differences in the current response between the inlet and outlet stocks and that water temperature plays only a minor role in the migration of rainbow trout fry to the lake. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 56-66). Also available on the World Wide Web.

M.Sc. / Please refer to full text to view abstract

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 trout, Oncorhynchus mykiss, on their reproductive performance and physiology and that of their progeny. Stress was administered over the period of early vitellogenesis (one and a half months), late vitellogenesis-final maturation (one and a half months), or during both periods (three months). Each stress treatment and control was triplicated with eight females in each replicate (n=24 fish per treatment). The eggs and progeny of each female were kept separate and observations made for four months after transfer to rearing tanks. Cortisol levels were measured in plasma, ovarian fluid and eggs by radioimmunoassay. Fish that experienced stress during final maturation and those that were under stress during the whole experiment spawned on average two weeks earlier than the control group. In contrast, fish stressed during the period of early vitellogenesis spawned at the same time as the controls. Absolute fecundity and fertilization were not significantly affected in any treatment group; however, significant differences were found in relative fecundity. Stress applied early in vitellogenesis resulted in smaller eggs and swim-up fry; but, these differences were not found in juveniles 8 weeks after hatching. Furthermore, we found no differences in survival of the progeny or resistance to the fish pathogen Vibrio anguillarum. Circulating levels of cortisol were high at ovulation in all groups, but significantly less cortisol was observed in the ovarian fluid and eggs. Sex hormone concentrations were high in plasma; however, they were several orders of magnitude lower in the ovarian fluid. These differences were not as extreme as those observed for cortisol. Lower levels of cortisol and sex steroids in ovarian fluid and eggs compared to that which is available from plasma suggests that there is a mechanism by which the female protects the eggs from potentially deleterious effects of prolonged exposure to elevated concentrations of steroids. / Graduation date: 1996

Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Graduation date: 1994

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 39-43). Also available on the World Wide Web.

Graduation date: 1996

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains vii, 33 p. : ill. Includes abstract. Includes bibliographical references (p. 19-24).