Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 107-114). Also available on the World Wide Web.

Thesis (M.S.)--University of Alaska Fairbanks, 2010. / Title from PDF t.p. (viewed Apr. 22, 2010). Includes bibliographical references (p. 48-55).

Broad Whitefish are an anadromous Arctic fish species in the Mackenzie River Valley, N.W.T. that undergo extensive spawning migrations to spawning grounds located on tributaries of the Mackenzie River, like the Arctic Red River. These spawning migrations occur annually between mid-October and early November as demonstrated with catch-per-unit-effort. The maturity stage development of Broad Whitefish is can be predicted by using the variables by gonad-weight and timing of migration for both female and male Broad Whitefish; however, male Broad Whitefish maturity stage also requires the variable abundance for prediction. At the time of Broad Whitefish migration the river environment has slow flowing water as documented by current profiles. The water velocity speeds present in the river at the time of migration are not a barrier to Broad Whitefish migration as Broad Whitefish can swim against water velocities 4 to 10 times higher. This research contributes important life history, migrating characteristic and swimming ability information to the knowledge of Broad Whitefish in the Mackenzie River System.

Broad Whitefish are an anadromous Arctic fish species in the Mackenzie River Valley, N.W.T. that undergo extensive spawning migrations to spawning grounds located on tributaries of the Mackenzie River, like the Arctic Red River. These spawning migrations occur annually between mid-October and early November as demonstrated with catch-per-unit-effort. The maturity stage development of Broad Whitefish is can be predicted by using the variables by gonad-weight and timing of migration for both female and male Broad Whitefish; however, male Broad Whitefish maturity stage also requires the variable abundance for prediction. At the time of Broad Whitefish migration the river environment has slow flowing water as documented by current profiles. The water velocity speeds present in the river at the time of migration are not a barrier to Broad Whitefish migration as Broad Whitefish can swim against water velocities 4 to 10 times higher. This research contributes important life history, migrating characteristic and swimming ability information to the knowledge of Broad Whitefish in the Mackenzie River System.

Thesis (M.S.)--University of Wisconsin--Stevens Point, 2007. / Includes bibliographical references (leaves 68-77).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1971. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.

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.

The mechanisms behind speciation have been subject of debate for centuries. The presence of resource polymorphism has been discovered to play a significant part in this process, and has been proven to induce phenotypic and genetic divergence. Although resource polymorphism has been intensely studied during the last few decades, there is a gap of information as to why this can be observed in some systems but not in others. Recent studies of European whitefish (Coregonus lavaretus) in Scandinavian lakes have shown that predation, in this case by Northern pike (Esox lucius), could be the factor that induces resource polymorphism. European whitefish is known to diverge into several ecomorphs in Scandinavian lakes, but only in the presence of pike. Divergence is assumed to be caused by the size selectivity of pike, and the following niche separation and eventually reproductive isolation. In this study, pike prey selectivity was studied in the field through sample fishing using hooks baited with whitefish of different sizes. The hypothesis was that pike prefers smaller prey over larger and mainly hunts in the littoral zone. This should causes smaller whitefish ecomorphs to be prone to predation in the littoral and thus utilize refuge spawning grounds with low predation pressure. However, no pike were caught on whitefish spawning grounds, and fishing at two additional pike rich sites displayed a preference towards medium-sized whitefish (p < 0.05). This indicates a size selectivity, although further and improved studies would be required to answer the question of the pike’s role in resource polymorphism.

In resource polymorphism, ecological opportunity and selective predatory pressure can be considered key factors in phenotypic divergence. In post-glacial lakes of Scandinavia, the European whitefish (Coregonus lavaretus L.) is a common species and has repeatedly diverged along the benthic - pelagic resource axis. Recent studies suggest that predation by northern pike (Esox lucius L.) induces rapid divergence in whitefish, leading to two reproductively isolated ecotypes: a dwarf planktivore and a giant benthivore. In lakes where pike is absent, whitefish are only found as monomorphic populations. In this study I estimated growth rates in two monomorphic and two polymorphic populations having giant and dwarf ecotypes. The aim was to use growth rates as a tool to distinguish between juvenile giants and dwarfs, but also to find out if a population's resource use was reflected in the growth rate. Scales were used to calculate growth rate, where like trees, variations in seasonal growth could be observed in a ring-like structure. Growth rates differed between the morphs, and mirrored their use of resources. The two monomorphic populations had the highest average growth rate the first six years (40.1 and 35.5 mm/year), and quickly reached maximum size. Dwarfs and giants in the dimorphic systems had equal growth the first two years, after which giants grew at a substantially higher rate. Categorization between juvenile giants and dwarfs could be done if an individual had passed its third growth season.