Comparison of North American and Nordic Gillnetting Standards to Describe the Fish Community Size Spectrum in Ontario Lakes

Size spectrum theory has been long applied in marine fisheries to assess the changes in fish communities associated with exploitation and/or environmental change. Size spectra describe the relationship between organism size and abundance, and provide single measures of the predator-prey dynamics, growth and productivity within a fish community. In this study, size spectra were calculated for lakes in Ontario that were sampled using the North American standard gillnetting design, a modified form of that approach used in Ontario and Nordic gillnetting. These sampling designs differ in the dimensions of gill nets, the range of mesh sizes, and the time deployed in the water, which are factors that can influence the selectivity of fish with different body sizes. The objectives of this study were to determine how well these netting approaches capture fish community productivity within Ontario’s lakes, and examine the regional differences in size spectra and possible causes for those differences.