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.

Thesis (M.S.)--University of Wisconsin--Stevens Point, 2006. / Includes bibliographical references (leaves 28-38).

Most fish species tend to feed on larger prey as their size increases. The lack of suitable prey during critical periods of their life can prevent them from shifting their diet to larger prey and also from reaching larger body sizes. In this study, we compared the energy budget of lake trout ( Salvelinus namaycush) populations with contrasting food webs. Non-piscivorous lake trout (NPLT) populations reached a much smaller size and grew at a much slower rate than picivorous lake trout (PLT) populations. Food consumption rates were on average, 2--3 times higher in NPLT when they were expressed on a wet weight basis. However, only a slight difference in their energy intake was detected (less than 10%) once consumption rates were corrected for differences in prey caloric content. Growth efficiency was about two times lower in NPLT compared to PLT, while their metabolic costs were higher and assimilation efficiency was lower. It is most likely that the increased metabolic costs were associated with higher foraging costs, since more feeding attempts must be made to acquire a given quantity of food when fish are feeding on smaller prey. Furthermore, the portion of indigestible matter is likely to be higher in the diet of NPLT than in PLT (e.g. chitin versus bone). These results are consistent with theoretical models of fish growth that have showed that lake trout must have access to larger prey, even if they are rare, to reach larger body sizes. Our study also illustrates how the restructuring of a prey community by the arrival of an exotic species into a food web could alter the growth rate of a top predator. Furthermore, our study suggests that age at first maturity is influenced by growth efficiency in indigenous populations of fish. Therefore, the dynamic of a population and its vulnerability to exploitation are likely to be influenced by their energy allocation strategy.

No description available.

Lake trout (Salvelinus namaycush) have a broad distribution across Canada’s north, yet most studies that describe reproductive habitat and behaviour have been conducted in the southern extent of their range. Northern regions are experiencing unprecedented changes from climate and industrial development, and thus there is a pressing need to understand the reproductive habitat and behaviour of this species. I examined a dozen sites around Alexie Lake, Northwest Territories, to test if physical habitat and wind exposure were important determinants of spawning site use and embryonic survival. Spawning was found to occur in ~2 m water depth, on 3–15 cm diameter clean substrate on the leading edge of shoals that ended in a rock crib rising abruptly in nearshore regions around the lake. Wind direction was predominantly from the west, although it was highly variable within and among spawning seasons. I found evidence of lake trout spawning at each site examined, which was not limited to shoals facing a predominant wind direction. High variation in embryonic survival (2–83%) from incubation trays was observed among spawning sites, demonstrating a large gradient in habitat quality exists within a given lake. However, modelled wind exposure did not predict embryonic survival, nor did physical characteristics - including shoal depth and slope, as well as cobble size and shape - that may influence interstitial water flow on spawning shoals. Using an acoustic telemetry monitoring system and novel spatial temporal clustering analysis, I was able to quantify lake trout spawning movements and behaviours over the course of an entire spawning season. Lake trout formed clusters on spawning shoals around the entire nearshore region, as well as around several islands, confirming that suitable spawning habitat is abundant in Alexie Lake. Males arrived on spawning shoals earlier than females and remained longer for a maximum of 25 consecutive days; females occupied spawning shoals for a maximum of 8 consecutive days over the course of the spawning season. Males formed over four times as many spawning clusters and visited twice as many sites than females. Spawning clusters were predominantly formed at night but were also observed during daylight hours, especially during the peak spawning season (September 9–19). I found males had higher activity rates, and spent longer periods on spawning shoals, than females, in spite of similar daily travel distances between sexes. Overall, my findings challenge the conventional role of wind as a predominant predictor of lake trout spawning site quality. I propose that the unpredictable nature of wind and abundance of suitable habitat may favour lake-wide spawning by lake trout as a bet-hedging strategy in northern lakes with limited fetch. / May 2016

Lake trout (Salvelinus namaycush) were extirpated from Lake Champlain around 1900 and from the lower four Great Lakes by 1960. Their ecological, commercial and recreational importance has prompted extensive restoration efforts. Despite widespread evidence of natural reproduction by stocked lake trout, there is minimal evidence of survival of wild progeny beyond age-0. Various abiotic and biotic impediments may be preventing self-sustaining lake trout populations from becoming established. Unsuccessful restoration in shallow areas has recently prompted a shift to restoration efforts to offshore, deep reefs in the Great Lakes. The first objective of this study was to develop, test, and implement methods for evaluating lake trout reproduction in deep water, where previously established techniques were ineffective. The second objective addressed the recruitment bottleneck between the emergent fry and juvenile life stages in Lake Champlain, by assessing the severity of predation on lake trout fry by epi-benthic fish. In order to quantify egg density on deep-water habitats (>18 m), we paired a deep-water egg trap with egg bags to establish a relationship between the two types of gear in Lake Champlain. There was no significant difference between densities in the egg bags and deep-water traps, but there was a positive correlation of their ranks (correlation coefficient = 0.514, p<0.0001). The deep-water traps were then used in Lake Michigan to successfully acquire the first egg density data from two sites on the deep Mid Lake Reef Complex. A drop electroshocker was developed to detect fry presence and tested in Lake Champlain in conjunction with emergent fry traps. Both types of gear exhibited similar patterns of fry relative abundance. To assess fry predation in Lake Champlain, two-hour gillnet sets during the period of fry emergence to identify fry predators and to describe how predation patterns changed diurnally and temporally. Seven species of epi-benthic fry predators were identified, including five species that had not been previously identified as fry predators. Yellow perch and rock bass dominated the predator community at two study sites (83% of total catch, N=1179, 77% of all fry predators, N=57). Predator presence and fry consumption was almost entirely nocturnal. There was a linear aggregational response in predator CPUE (fish/hr) to increasing fry relative abundance (p<0.033) but confirmed predators did not exhibit a functional response. There was evidence of a threshold of fry relative abundance at 1 fry/trap/day for the onset and conclusion of fry predation. Temperature was a driving factor in the timing of fry emergence and predator abundance, allowing us to predict the relative impact of predators based on temperature scenarios. Only 5% of the potential predators consumed fry. We used empirical probabilities of consumption to model loss of fry due to predation. This consumption model revealed that predator abundances would have to be extremely high for predation to significantly reduce the population of fry. However, given the relatively high species richness of predators observed at the shallow water study sites, lake trout fry survival is likely to be higher at deep, offshore reefs. These results support the recent shift in restoration efforts to focus on deep reefs.

Climate change may lead to declines in lake trout (Salvelinus namaycush) populations and change the structure of the ecosystem in which they live. The lake trout is a keystone species in ecosystems of northern temperate lakes and these declines may subsequently reduce the genetic diversity found in these salmonids. Populations that contain greater genetic variation may have an increased capacity to adapt to changes in the ecosystem. Therefore, an understanding of the genetic diversity found in lake trout populations is required for their effective conservation and management. As a result, this study aimed to examine the genetic diversity and phylogeography of lake trout populations in north central Canada.<p>The genetic diversity of lake trout from 19 lakes in Saskatchewan was examined using partial regions of the ND2 and ND5 mtDNA genes. A total of 607 tissue samples were analyzed using PCR-based single stranded conformation polymorphism (SSCP) and DNA sequencing. Although the ND5 gene fragment had minimal intraspecific variation, eleven sequence types were detected in the ND2 gene. Each sequence type differed in relative frequency between and among the lake trout populations sampled. <p>One particular southern lake trout population, Crean Lake, had markedly different genetic composition in comparison to other lakes in the region. In the 1950s and 1960s, Crean Lake was stocked with lake trout from neighbouring Wassegam Lake in an attempt to increase population numbers. The sequence types of Crean Lake trout and their relative frequencies were dramatically different to those in Wassegam Lake. This suggests that the stocked fish may have been unsuccessful in their establishment/reproduction within Crean Lake. Lake trout from this lake also contained the highest frequency (44%) of rare ND2 sequence type B. Sequence type B was only detected in one other lake (La Ronge), at a very low frequency. <p>The mutational changes in the eleven ND2 mitochondrial DNA sequence types represented three different amino acid sequence types. Substitutions of Threonine and Isoleucine occurred, resulting in two polar amino acids with much different hydropathy indexes. This may affect the tertiary structure of the protein, possibly indicating functional differences. Functionally different proteins may be exhibiting characteristics that allow lake trout to flourish in their environment. <p>The fragments of both the ND2 and ND5 genes proved to be valuable for phylogenetic analyses within the Salmonidae. The genetic markers established in the present study provide the basis for future work on population genetics of lake trout. It would be advantageous to broaden the area of study in order to compare the genetic diversity found within the study area to other regions of Canada. This would determine whether the genetic diversity detected in this study is significantly greater than in other populations at a national scale. Management strategies should ultimately attempt to conserve the genetic diversity found within the lake trout populations of north central Saskatchewan.

Climate change may lead to declines in lake trout (Salvelinus namaycush) populations and change the structure of the ecosystem in which they live. The lake trout is a keystone species in ecosystems of northern temperate lakes and these declines may subsequently reduce the genetic diversity found in these salmonids. Populations that contain greater genetic variation may have an increased capacity to adapt to changes in the ecosystem. Therefore, an understanding of the genetic diversity found in lake trout populations is required for their effective conservation and management. As a result, this study aimed to examine the genetic diversity and phylogeography of lake trout populations in north central Canada.<p>The genetic diversity of lake trout from 19 lakes in Saskatchewan was examined using partial regions of the ND2 and ND5 mtDNA genes. A total of 607 tissue samples were analyzed using PCR-based single stranded conformation polymorphism (SSCP) and DNA sequencing. Although the ND5 gene fragment had minimal intraspecific variation, eleven sequence types were detected in the ND2 gene. Each sequence type differed in relative frequency between and among the lake trout populations sampled. <p>One particular southern lake trout population, Crean Lake, had markedly different genetic composition in comparison to other lakes in the region. In the 1950s and 1960s, Crean Lake was stocked with lake trout from neighbouring Wassegam Lake in an attempt to increase population numbers. The sequence types of Crean Lake trout and their relative frequencies were dramatically different to those in Wassegam Lake. This suggests that the stocked fish may have been unsuccessful in their establishment/reproduction within Crean Lake. Lake trout from this lake also contained the highest frequency (44%) of rare ND2 sequence type B. Sequence type B was only detected in one other lake (La Ronge), at a very low frequency. <p>The mutational changes in the eleven ND2 mitochondrial DNA sequence types represented three different amino acid sequence types. Substitutions of Threonine and Isoleucine occurred, resulting in two polar amino acids with much different hydropathy indexes. This may affect the tertiary structure of the protein, possibly indicating functional differences. Functionally different proteins may be exhibiting characteristics that allow lake trout to flourish in their environment. <p>The fragments of both the ND2 and ND5 genes proved to be valuable for phylogenetic analyses within the Salmonidae. The genetic markers established in the present study provide the basis for future work on population genetics of lake trout. It would be advantageous to broaden the area of study in order to compare the genetic diversity found within the study area to other regions of Canada. This would determine whether the genetic diversity detected in this study is significantly greater than in other populations at a national scale. Management strategies should ultimately attempt to conserve the genetic diversity found within the lake trout populations of north central Saskatchewan.

The objective of this thesis was to assess the physical (concentrations, durations, and sedimentation) and biological effects of total suspended solids (TSS) in Arctic lakes following in-lake construction of dikes. TSS concentration and duration estimates were applied in a Severity of Ill Effects model which predicted possible habitat degradation and a reduction of feeding of salmonids with no significant difference between stations (ANOVA, p=0.153). Benthic invertebrates collected inside suspended sediment containment curtains showed a decrease in richness and abundance (Tukey’s, p<0.05), with no effects elsewhere. Stable isotope analysis from lake trout and arctic char muscle tissue suggested no differences in isotopic signatures following TSS exposure, but stable isotope analysis of stomach contents in lake trout had a significant increase in δ15N compared to the reference basin (Tukey’s, p<0.05). These findings suggested that lake trout adapted their food sources under moderate TSS exposure and benthic invertebrates rapidly recovered to pre-disturbance values. / Agnico-Eagle Mines Limited: Meadowbank Division and the University of Guelph; Research approved by Department of Fisheries and Oceans & Nunavut Impact Review Board

Cumulative effects, often minor individually but collectively significant, are continually being grappled with by researchers, policy makers and practitioners. Despite this the Canadian approach to cumulative effects assessment is thought by many to be ineffective. In this thesis I investigate the literature that surrounds cumulative effects and uncovered three distinct themes that occur chronologically: genesis, project-based approach and integration. During the genesis phase cumulative effects nomenclature, ideas and frameworks was created. The main theme of this era was to asses these effects at a large scale and to have a strong understanding of a systems ecology prior to the assessment. This approach was found to be too complex and so a more narrow project-based approach was implemented and still remains today. This approach is heavily criticized and as such researchers are now trying to find an approach that integrates these two divergent themes into a regional level assessment. I have found there to be several frameworks but an absence of effective regional methodologies. There is a need for regional metrics if this approach is to ever be institutionally supported. Food web structure can be evaluated at multiple scales and has been shown to be responsive to environmental variation; thus, it has potential for application as a metric for cumulative effects. Here, using stable isotope analysis, I field test integrative measures of food web structure (food chain length, habitat coupling, trophic omnivory) at sites of varying degrees of anthropogenic stressors in Georgian Bay, Ontario to evaluate the use of food webs as a metric for cumulative effects assessment. I found that food web structure varied significantly among sites. Sites with high levels of stress displayed structural characteristics reflective of human activities such as shorter food chain lengths, increased trophic omnivory, and reduced habitat coupling relative to the non-stressed sites. These results indicate that food web structure as an ecosystem level metric may provide insight into anthropogenic activities, and may be applied routinely as a metric for doing Cumulative Effects Assessment. / University of Guelph, Saugeen Ojibway Nation, Georgian Bay Forever