This study developed a robust technique for the assessment of morphometric differences among overwintering northern fish populations. Arctic charr were sampled soon before the freeze-up and just after ice break-up at two subarctic Quebec lakes. A homogenous sample of 397 fish was used. Regression analyses of the length-weight relationships and their derived condition indices were insufficient, due to their inherent limitations, to recognize the differences between sampling groups. A series of multivariate analyses (canonical, stepwise and discriminant analysis), based on eleven morphometric characters of the fish, provided a better assessment. The analysis recognized the distinctions between sampling groups, correctly classified 70-100% of the fish into their appropriate groupings, and indicated that body height measured at the anal opening was the most discriminatory variable. Landmark variables related to shape differences were effective in discriminating fish according to their lake of origin, whereas length and weight variables, which closely reflected the size differences, were better at distinguishing seasonal changes. The study provides a simple, efficient assessment method based on phenotypic variations to explain different survival strategies, and the associated life history traits, adopted by fish.

No description available.

No description available.

The Arctic charr (Salvelinus alpinus) is a top predator in northern lakes and accumulates persistent lipophilic contaminants. Toxaphene, a major organochlorine contaminant in Arctic charr, is known to be acutely toxic to fish but the effects of dietary exposure have not been examined. Furthermore, lake-resident Arctic charr are frequently infected with larvae of the cestode, Diphyllobothrium dendriticum. The objective of this study was to investigate the effects of toxaphene exposure on Arctic charr growth, nutritional quality, physiology, and susceptibility to infections of D. dendriticum. A preliminary experiment found no effect of toxaphene on charr visceral organ and fat weights, plasma Vitamin A and E and plasma cortisol, although dominance hierarchies within groups may have masked treatment effects. For the main experiment, hatchery-reared Arctic charr were subjected to one of four treatments: (i) a single oral dose of corn oil (control); (ii) a single oral dose of 10 mug/g wet weight toxaphene dissolved in corn oil; (iii) exposure to 15 larval D. dendriticum; and (iv) a combination of both. (Abstract shortened by UMI.)

No description available.

No description available.

Lake Vättern has been contaminated with high levels of polychlorinated biphenyls (PCBs) for decades, which could be due to the release of wastes from industries and urban communities surrounding the water system. This has especially had a negative effect on fatty fishes, which could accumulate large amounts of persistent organic pollutants (POPs) and thereby also become a source of environmental toxicants to humans through consumption. Most PCB analysis only quantify a handful of congeners, the so called indicator-PCBs (I-PCBs), but this might leave out important information. In this study, an existing analytical method was improved by supplementing with additional congeners to detect a larger set of PCB congeners in Arctic char (Salvelinus salvelinus) and European whitefish (Coregonus acronius) caught from Lake Vättern, Sweden. New pre-packed multilayer silica columns from CAPE technologies were tested and used to pretreat the fish samples prior to analysis with a Gas Chromatograph coupled to low-resolution Mass Spectrometer using Atmospheric Pressure Ionization (API GC/MS). It was found that modifications of the clean up method for PCBs were necessary, such as lowering the amount of hexane in the washing step and combining the two eluent fractions. The Arctic char and the European whitefish showed a fat content of 0.18% and 0.74%, respectively. Concentrations of detected congeners ranged from 0.5 to 1470 pg g-1 fresh weight (fw) in Arctic char and varied between 1.2 to 6550 pg g-1 in European whitefish. For Arctic char and European whitefish, the WHO2005-TEQ values were 0.4 pg g-1 fw and 0.6 pg g-1 fw, respectively. The greatest total PCB concentration of 25900 pg g-1 was measured in European whitefish. The total concentration of I-PCBs (#28, 52, 101, 138, 153, 180) was 3710 pg g-1 for the Arctic char and 13900e pg g-1 for the European whitefish. All obtained results were lower than those reported from other studies. Constructed congener profiles show that the two species have similar ratios of PCB #138 and #153. Differences are observed of PCBs with a higher chlorination grade, probably due to differences in migration patterns, habitats of the lake, diets, metabolism or bioaccumulation.

Trophic ecology is a key component in describing patterns of variation between and within populations, particularly in Arctic marine systems wherein climate change is impacting food webs. This thesis investigates the trophic ecology of Arctic char (Salvelinus alpinus) in the Cumberland Sound region using a multi-indicator approach. My data show trophic niche differences between resident and anadromous ecotypes and evidence for estuarine feeding by residents. I document a shift in the marine diet of Arctic char from zooplankton to capelin (Mallotus villosus) – a novel prey species in this region – that has occurred in less than a decade. Changes in Arctic char growth imply population-level effects of this shift; however, more research is required. Finally, I find lipid effects on δ13C and lipid-extraction effects on δ15N and δ34S for Arctic char muscle tissue. Lipid-correction models did not provide adequate δ13C estimates; thus, chemical extraction or ecotype-specific validation of models is recommended.

Arctic charr are susceptible to cestodes like Diphyllobothrium dendriticum which are transmitted through the food web. Field studies investigating Arctic charr-Diphyllobothrium relationships often provide little data from which to fully understand Diphyllobothrium transmission or to assess their impact on copepod or fish hosts. Experimental studies may, therefore, be the only direct way to investigate these issues. The research goal of this thesis was to duplicate the D. dendriticum life cycle in the laboratory to investigate parasite development and host specificity, and to apply the experimental data to natural situations. Results indicated that at 10°C, D. dendriticum eggs develop slowly and 65 days are required for complete embryonation. In many Canadian Arctic lakes water temperatures rarely exceed 4°C, and this study has shown that at this temperature embryonation requires several months, necessitating more than one ice-free season for life cycle completion. The results also showed that embryos developed more rapidly and significantly more eggs hatched when incubated with light or aeration, results that were consistent for D. dendriticum originating from Canada and Norway. To continue the life cycle, coracidia must be consumed by suitable copepod hosts. This study showed that although D. dendriticum will infect the European copepods Cyclops scutifer and Eudiaptomus graciloides, prevalence was higher and procercoids developed more rapidly in E. graciloides. These results showed that E. graciloides is a better host for D. dendriticum than is C. scutifer, contradicting published literature. In North America, E. graciloides is not found in lakes containing D. dendriticum and no North American calanoid species have been tested to determine their host suitability to this cestode. This study identified two North American species, Diaptomus minutus and D. leptopus, which are suitable laboratory hosts. D. minutus is almost certainly a natural host for D. den

Trophic ecology is a key component in describing patterns of variation between and within populations, particularly in Arctic marine systems wherein climate change is impacting food webs. This thesis investigates the trophic ecology of Arctic char (Salvelinus alpinus) in the Cumberland Sound region using a multi-indicator approach. My data show trophic niche differences between resident and anadromous ecotypes and evidence for estuarine feeding by residents. I document a shift in the marine diet of Arctic char from zooplankton to capelin (Mallotus villosus) – a novel prey species in this region – that has occurred in less than a decade. Changes in Arctic char growth imply population-level effects of this shift; however, more research is required. Finally, I find lipid effects on δ13C and lipid-extraction effects on δ15N and δ34S for Arctic char muscle tissue. Lipid-correction models did not provide adequate δ13C estimates; thus, chemical extraction or ecotype-specific validation of models is recommended.