CCFFR/SCL : Abstracts of Oral Presentations—alphabetical order Addison , P. A. 1 *, C. C. Wilson 2 , and. B. J. Shuter 1 . 1 Zoology Department, University of Toronto, Toronto, Ontario; 2 Ministry of Natural Resources and Trent University, Peterborough, Ontario. (email:paddison@trentu.ca) ASSESSING GENETIC DIVERSITY OF SPAWNING RAINBOW TROUT IN TRIBUTARIES OF LAKE SUPERIOR ALONG THE ONTARIO SHORELINE. Studies assessing the genetic structure of migratory Pacific salmonids within their native range have been vital to establishing effective management units. However, for Great Lakes populations, genetic assessment has been limited and population structure remains generally undetermined. Naturalized populations of migratory rainbow trout ( Oncorhynchus mykiss ) in tributaries between Thunder Bay and Marathon, Ontario, have had at least 85 years since initial colonization and limited influence from subsequent supplemental stocking, both of which have contributed to the opportunity for population divergence. Adults from nine tributaries will be used as a model system to study genetic diversity and to identify the most appropriate management units. Rainbow trout were non-lethally sampled by angling during their spring spawning run. A 5mm circle of fin tissue was excised for genetic analysis and scales, length and sex taken to obtain life history information. Multilocus genotypes for 30-50 individuals from each tributary will be measured using 11 microsatellite loci. Results will be compared among fish from different tributaries to assess suitability of current management strategies. * Aherne, J., and Dillon, P.J. Environmental Resource Studies, Trent University, Peterborough, ON, K9J 7B8 LONG-TERM TRENDS IN THE CHEMISTRY OF PRECIPITATION AND LAKE WATER IN SOUTH- CENTRAL ONTARIO, CANADA North American agreements to reduce the emissions of acidifying pollutants have resulted in major changes in the deposition of sulphur across Ontario in the past 20 years. Long-term deposition and lake chemistry (~30 lakes) data for the period 1980–1999 were used to determine the response of surface waters in south-central Ontario to reductions in emissions. Trends in chemical parameters were estimated using the Mann-Kendall test. Results suggest a widespread reduction in sulphate concentration; however reduction in calcium concentrations appear to have partially offset the influence of sulphate reduction on lake acidity. Fluctuation in climatic factors over the monitoring period have led to significant inter-annual variability, emphasising the need for long-term monitoring if underlying trends are to be identified. * Aherne , J. (1), Larssen, T. (2), and Dillon, P.J. (1) (1) Environmental Resource Studies, Trent University, Peterborough, ON, K9J 7B8; (2) Norwegian Institute for Water Research, Oslo, Norway MODELLING THE FUTURE WATER CHEMISTRY OF LAKES IN SOUTH-CENTRAL ONTARIO, CANADA During the 1970s and 1980s, the acidification of surface waters by atmospherically deposited sulphur (S) became a major international concern. Major S emission control programs were implemented in North America, resulting in current emissions being ~30% less than in 1980. However, the level of acidic deposition remaining is still unlikely to promote widespread recovery of aquatic ecosystems. As such, there is an increased need to know whether future proposed reductions will be sufficient to promote ecosystem recovery, and when (chemical) recovery is likely to occur. To address these issues, dynamic soil chemical models, such as MAGIC (model of acidification of groundwater in catchments), are required. The predictive power of models is a crucial issue for determining their usefulness to support policymaking. MAGIC was used to predict recovery of lakes in south-central Ontario to proposed future emission reductions. Calibration of the lakes to the observed trends (1980–1999) considerably increased the robustness of the model predictions. Archambault * 1 , P., S. Dimitriadis 2 and P. Sirois 2 . 2 Division des sciences environnementales, Ministère des Pêches et des Océans, Institut Maurice-Lamontagne, Mont-Joli, QC. 1 Département des sciences fondamentales, Université du Québec à Chicoutimi, Chicoutimi, QC (email: archambaultp@dfo-mpo.gc.ca).
STOCKING FISHLESS LAKES: INFLUENCE OF BROOK TROUT ON MESOZOOPLANKTON COMMUNITY STRUCTURE OF BOREAL SHIELD LAKES IN THE SAGUENAY REGION Interactions between wild and stocked brook trout, Salvelinus fontinalis , as well as competing invertebrate predators like Chaoborus (Insecta: Diptera) have both positive and negative effects on the mesozooplankton structure of Boreal Shield lakes and the identification of such impacts is closely tied to analytical methods. In this study, three hypotheses were tested using univariate and multivariate analyses: (a) wild and stocked brook trout exert equally strong influences on Boreal Shield lacustrine mesozooplankton structure in eastern Canada (with significant differences expected between brook trout lakes (naturally present or stocked) and fishless lakes); (b) mesozooplankton species assemblages were expected to be different between individual lakes with fish and fishless lakes resulting from top-down control by fish and/or invertebrate predation; (c) species-specific body size was expected to decrease in the presence of fish. The study found that multivariate metrics are more sensitive than univariate metrics in identifying changes amongst mesozooplankton species assemblages related to fish stocking of fishless lakes. The strength of this response was somewhat unexpected since the diet of brook trout is thought to be primarily composed of zoobenthos in the absence of other fish species. Indeed, statistical analysis of the body size distribution of pelagic mesozooplankton revealed that inter-lake differences were most likely due to a combination of invertebrate and trout planktivory than correspondence with measured abiotic factors. Chaoborus , in particular, exerted a strong intermediary influence on the species composition and body size of mesozooplankton assemblages acting as both prey and predators in the system. * Badiou , P.H.(1), and Goldsborough, L.G. (1) (1) Department of Botany, University of Manitoba, Winnipeg, MB, R2H 1Y5 THE COMMON CARP ( CYPRINUS CARPIO ) IN MANITOBA: IMPACTS AND EXPANSION OF AN EXOTIC BENTHIVOROUS FISH The common carp is arguably the most successful exotic fish species worldwide and has been well established throughout North America for decades. Recent findings from Manitoba suggest that the common carp has now invaded the Churchill River system and is moving northward. Although there have been many studies which have examined the impacts of the common carp on aquatic ecosystems, only a few have been carried out at the whole ecosystem level. To determine the effects of the common carp on wetland ecosystems, 5 large (5 - 7 ha) experimental wetlands were stocked with increasing densities of carp (0, 150, 300, 600, and 1200 kg/ha) in 2001 and 2002. Additionally, as most studies examining the impacts of carp have used small mesocosm experiments, we conducted a parallel experiment in 2002 where carp were stocked in small (5m x 5m) wetland enclosures. Experiments conducted in the large experimental wetlands indicated that total suspended solids, rates of sedimentation, and concentrations of dissolved phosphorus increased in a linear fashion with increasing carp biomass. Conversely dissolved oxygen concentrations decreased with increasing densities of carp. Additionally, results indicated that sedimentation rates, measured over short time intervals (5-7 days) were much better at predicting the level of carp activity compared to measuring the concentration of total suspended solids which has traditionally been used to estimate the impact of benthivorous fish. Similar changes in water quality were observed in experiments conducted in small enclosures, with the exception that impacts were much more pronounced. Bailey *, J. L. and R. C. Bailey. Department of Biology, The University of Western Ontario, London, Ontario (email:jbaile3@uwo.ca) CORRELATION OF FISH COMMUNITIES AND MULTI-SCALE ENVIRONMENTAL DESCRIPTORS IN WADEABLE STREAMS OF THE YUKON RIVER BASIN We sampled fish at thirty wadeable stream sites in the Yukon River basin in Yukon Territory, Canada during July, 2004, to establish reference conditions for fish in Yukon River basin stream communities We also measured water quality (eg. temperature, dissolved oxygen, conductivity, pH), stream flow, substrate characteristics and riparian vegetation at each site. In addition, catchment area, catchment land cover, and distance of each site to major water bodies and stream barriers were determined through Geographic Information System and satellite photography analysis. Fish community structure and its relationships with the multi-scale description of the stream environment were quantified with non-metric multidimensional scaling, principal component analysis, and correlation analysis. * Beauvais , S., del Giorgio, P.A., Longhi, L.M,. and Prairie, Y.T. Département des Sciences Biologiques, UQÀM, Succursale Centre-Ville, CP 8888, Montréal, Qc, H3C 3P8
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