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.

Lake whitefish (Coregonus clupeaformis) are an ecologically, culturally and economically important species throughout the Great Lakes. Studying the larval period of ontogeny is important to increasing knowledge of population dynamics and monitoring ecological changes in lake whitefish populations. Larval lake whitefish have been studied across the Great Lakes since the 1930’s; however, there are major gaps in our understanding of the factors that affect distribution and abundance of larval lake whitefish. The goal of this study was to investigate the distribution and abundance of larval lake whitefish in a Great Lakes embayment, using Stokes Bay, Lake Huron as a case study. Plankton samples and environmental data were collected from mid-spring to early summer during 2011 and 2012. Plankton tows in 2011 (n=71, 21 April-03 June) revealed relatively high densities of larval lake whitefish as compared to other Great Lakes studies. Overall there was little relationship between environmental variables (temperature, dissolved oxygen, conductivity, depth) and larval lake whitefish distribution and abundance. Plankton tows in 2012 (n=25, 25 April-23 May) revealed a virtual absence of larval lake whitefish in Stokes Bay. The apparent 2012 year-class failure was concurrent with unseasonably warm temperatures and reduced ice coverage. Temperature-related hypotheses are evaluated in context with other possible explanations of a general year-class failure of lake whitefish during early life history. / Saugeen Ojibway Nation (SON)

No description available.

This research focuses on the development, evaluation, and application of a mercury (Hg) mass balance model for predicting the accumulation of Hg in fish. This model requires accurate estimates of Hg elimination rate by fish and feeding rates to adequately predict Hg concentration in fish. An empirical model was developed to estimate Hg elimination by fish using data obtained from published experiments. This analysis showed that Hg elimination rate was overestimated in short-term experiments, positively correlated to water temperature, negatively correlated to body size, and that the elimination rate of inorganic Hg was faster than that of methylmercury. This empirical model was then incorporated in a Hg mass balance model to predict the concentration of Hg in fish. The Hg mass balance model accurately predicted Hg concentration in fish when it was combined with food consumption rates that were determined using a radioisotopic method. This analysis suggested that the parameters of the Hg mass balance model were adequate for predicting Hg concentration in fish. I also showed that Hg concentration tended to be underestimated by the Hg mass balance model when it was combined with feeding rates determined with a laboratory-derived bioenergetic model, probably because activity costs derived in the laboratory do not reflect activity costs of fish in the field. Beside predicting Hg concentration in fish, I showed that this mass balance model could also be used to estimate feeding rates of fish in the field by measuring the concentration of Hg in fish. This approach was validated using data obtained from a published experiment. It was also successfully tested using independent estimates of feeding rates obtained with a radioisotopic method. I applied this Hg mass balance model to compare the energy budget of sympatric populations of dwarf and normal whitefish (Coregonus clupeaformis). This analysis showed that dwarf whitefish consumed 40--50% more food than normal whitefi

Thesis (Ph. D.)--Michigan State University. Dept. of Fisheries and Wildlife, 2008. / Title from PDF t.p. (viewed Sept. 11, 2009). Includes bibliographical references. Also issued in print.

No description available.

Presence of Triaenophorus crassus Forel in the flesh of lake whitefish (Coregonus clupeaformis (Mitchill)) and cisco (C. artedi Lesueur) can be an important economic problem for commercial coregonine fisheries. This study was initiated during the development of native fisheries in northern Quebec. Coregonine populations from 6 lakes of the Nottaway watershed were sampled to determine infection patterns of T. crassus in relation to age and size of fish, and to document interlake differences in prevalence and number of T. crassus. Interspecific and interlake differences in the infection dynamics of T. crassus were described in relation to capsule types, sizes and plerocercoid conditions. Infection dynamics were also investigated with age of fish. All coregonine populations were infected with T. crassus, and cisco more so than lake whitefish where the two species co-occurred. Prevalence and number of T. crassus were independent of fish age and size in most lake whitefish populations. Number of T. crassus increased with fish age and size in all cisco populations, but prevalence increased only in the populations from the largest lakes. Interlake differences in prevalence and number of T. crassus were detected for both coregonine species, and were related to feeding behaviour of the fish and lake biophysical characteristics. Heavy infections in one lake whitefish population were mainly associated with piscivory. Interspecific and interlake differences in the infection dynamics of T. crassus were also observed. Differences in the proportions of capsule types, sizes, and plerocercoid conditions suggest that population turnover of T. crassus in cisco is faster than in lake whitefish. In contrast to previous studies, plerocercoid condition was found to be independent of capsule size. Coregonine populations, which did not differ in prevalence and number of T. crassus, showed some differences in the proportions of capsule types, sizes and plerocercoid conditions, suggesting

<p>Natural and constructed rocky reef habitats constitute important areas for lithophilic spawning fishes and their embryonic and larval offspring. Interstitial spaces created by the structure of rocky reefs create micro-environments where incubating embryos and juvenile fishes are potentially protected from predators. However, if interstitial spaces are filled or blocked by sediment deposition or biofouling, the reef structure may lose the protective benefits for embryonic and larval fish survival. Lake whitefish (<i>Coregonus clupeaformis</i>) and walleye (<i>Sander vitreus</i>) are native Great Lake lithophilic broadcast spawning fish that use rocky spawning habitats that are vulnerable to degradation caused by deposition of suspended sediments. To restore degraded rocky reef habitat, common practices include addition of material to existing reef structures or construction of new reefs, but both of these practices can be costly and time intensive. In this study, we measured the effect of different types and amounts of sediment cover on hatching success of walleye eggs and assessed if differences in female walleye (female length and egg size) account for tolerance to sediment cover. Additionally, we explored an alternative approach for reef restoration, custodial maintenance, in which we created two novel devices to potentially clean rocky reef habitat. We carried out two laboratory experiments in 2018 and 2019 to test the effect of sediment cover on hatching success of walleye eggs (2018) and to test how female identity and female length or egg size may interact with sediment cover to influence hatching success (2019). We exposed walleye eggs to instantaneous sediment cover (0 mm – 7mm) of either sand (course) or silt (fine) sediments from fertilization until day 15 of incubation. Our results indicated that walleye eggs were sensitive to silt cover (71% mortality- 2 mm cover silt) but not sand (47% mortality- 7mm cover sand). While there was an indication that hatching success was marginally related to female length and egg size, we concluded that sediment cover seemed to have similar effects on eggs, regardless of female length or egg size. The susceptibility of walleye eggs to mortality caused by sediment cover underscores the need for non-degraded spawning habitat. Our two cleaning devices used either propulsion or pressurized water jets to clean sediments from the rocky structure as they were towed behind a small vessel (i.e., did not require the use of SCUBA divers). We used devices to clean two natural rocky reefs in Saginaw Bay, Lake Huron in 2018 and 2019. We measured relative hardness before and after use of devices on cleaned and uncleaned study plots to determine effectiveness of devices. In addition, we measured egg deposition by fall (lake whitefish) and spring (walleye) lithophilic spawners on study plots to determine potential differences in fish usage of cleaned and uncleaned areas. We found that cleaning devices contributed to changes in relative hardness among study plots. Egg deposition was also variable on study plots but in general, egg deposition was consistently highest on treatment plots cleaned by our device that used propulsion. The practicality of cleaning devices was seemingly related to the magnitude of degradation of rocky reefs, nevertheless, our results show that the use of these or similar devices may potentially increase egg deposition by creating areas of higher-quality habitat. While more testing is necessary to fully understand the potential of our reef cleaning devices, this two-year study suggests that these devices may be capable of restoring degraded rocky spawning habitat which could potentially minimize the negative effects associated with sediment degradation on lithophilic spawning fish.</p>

No description available.