Lake and round whitefish are cold-adapted freshwater species with similar life histories and spawning behaviours. There have been several studies on the embryonic development of both species (particularly for lake whitefish), most utilizing constant temperatures. However, temperatures fluctuate in the field due to natural (e.g. seasonal changes) and anthropogenic (e.g. water discharged from once-through cooling processes) effects. Releases from once-through cooling processes may contain low levels of chemicals (e.g. morpholine) and radiation (e.g. tritium). This thesis examined and compared the impacts of thermal, morpholine, and radiation stressors on lake and round whitefish embryogenesis. To examine the effects of fluctuating incubation temperatures, lake and round whitefish were reared at constant temperatures, with seasonal temperature declines/inclines, transient temperature spikes, or seasonal temperature changes combined with temperature spikes. Round whitefish embryos had significantly higher mortality when reared at 8°C compared to lake whitefish, and seasonal temperature changes impacted development rate, growth, and hatch dynamics for both species. Temperature spikes had relatively little effect on development. The effects on embryonic development of chronic morpholine and low-dose radiation exposures were examined in round whitefish to compare with existing data in lake whitefish. Round whitefish embryos were more impacted by morpholine than lake whitefish (larger effects on growth and mortality at relatively lower concentrations) and v less impacted by low-dose radiation (little effect on growth or hatch dynamics). Post hatch, round whitefish embryos reared at 8°C, with rapid seasonal inclines, or with 500 mg L-1 morpholine had elevated mortality. All irradiated embryos had decreased mortality post-hatch compared to non-irradiated embryos. Thus, embryonic exposure to all stressors examined appears to alter post-hatch survival. This thesis better defines the effects of fluctuating incubation temperatures, chronic morpholine, and chronic radiation exposures on the embryonic development of lake and round whitefish. It also suggests that embryonic incubation conditions are important beyond hatching. / Thesis / Master of Science (MSc) / Lake and round whitefish are cold-adapted freshwater species. Both species play important ecological roles, with lake whitefish generally perceived as more economically and culturally important. Many studies have detailed lake whitefish embryonic development under constant stressors (e.g. temperature) but there are relatively few studies on round whitefish embryonic development. Both species experience seasonal temperature fluctuations in nature and may experience additional anthropogenic temperature, chemical, and radiation stress due to discharge from once-through cooling processes at thermal power plants, which may contain low levels of morpholine and radiation. Our study suggests that round whitefish embryos are more sensitive to elevated temperature and morpholine levels, but less impacted by chronic low-dose irradiation relative to lake whitefish embryos. The growth and development of both species are significantly affected by seasonal temperature changes.

Lake whitefish (Coregonus clupeaformis; LWF) are a cold-adapted freshwater species that are of both economic and cultural value. These fish spawn in lake areas where their embryos are exposed to thermal power plant effluents that may contain low levels of thermal, radiological and chemical stressors. Many studies on LWF embryonic development have looked at the individual effects of these stressors, but few have looked at the potential for combined effects. The combined effects of thermal and radiological stress were of interest due to growing evidence that mild thermal stress can produce an adaptive response, through the induction of the heat shock response (HSR), when followed with subsequent ionizing radiation stress. This thesis examined the combined impacts of thermal and radiological stress during LWF embryogenesis. LWF embryos were exposed to mild heat shocks (HS; Δ3 or 9°C) prior to a high dose of acute 137Cs gamma rays at 2, 6 and 24 hours post heat shock during the gastrulation or eyed stage. Heat shocked embryos were collected at each developmental stage and assessed for induction of heat shock protein (Hsp) genes. Following exposure, embryos were raised until hatch where mortality, morphometry, and embryo weight were measured. Mild HS induced Hsp70 mRNA expression at gastrulation, but not at the eyed stage. Embryos at hatch were not impacted by thermal or radiological exposure at the gastrulation stage. During the eyed stage, acute radiation treatment increased mortality and decreased body size at hatch. Mild HS prior to radiation did not provide protective effects and no adaptive response was observed. This thesis better defines the combined effects of thermal and radiological stress on the embryonic development of LWF. It also suggests that the ontogeny aspects of heat shock responses and radiosensitivity are important to consider for future adaptive response studies. / Thesis / Master of Science (MSc)

The mountain whitefish (Prosopium williamsoni) has been largely overlooked in population genetic analyses despite its wide distribution in discrete drainage basins in western North America for over four million years. Its closest sister taxa the Bear Lake whitefish (P. abyssicola), Bonneville cisco (P. gemmifer), and Bonneville whitefish (P. spilonotus) are found only in Bear Lake Idaho-Utah and were also included in the analyses. A total of 1,334 cytochrome b and 1,371 NADH dehydrogenase subunit 2 sequences from the Bonneville Basin, the Columbia River Sub-basin, the lower Snake River Sub-basin, the upper Snake River Sub-basin, the Green River Basin, the Lahontan Basin, and the Missouri Basin were examined to test for geographically based genetic differentiation between drainage basins and sub-basins and phylogeographic relationships to determine the invasion route of Prosopium into western North America and to aid in understanding current relationships. Prosopium entered the region via the Missouri River connection to Hudson Bay and moved in two waves: one colonized the lower Snake River Sub-basin, Columbia River Sub-basin, and the Lahontan Basin; the second wave colonized the upper Snake River Sub-basin, Bonneville Basin, Green River Basin, and established the Bear Lake Prosopium. Mountain whitefish exhibit a large amount of geographical genetic differentiation based on drainage basin except between the upper Snake River and the Bonneville Basin while the Bear Lake Prosopium show large amounts of gene flow between the three species. The apparent paraphyly of the mountain whitefish and the limited genetic structure of the Bear Lake Prosopium warrant recognition in the management of Prosopium and raise questions regarding species definitions in the group.

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