Comparative regional assessment of factors impacting freshwater fish biodiversity in Canada

This study presents a broad analysis of freshwater fish species biodiversity in relation to environmental and stress metrics throughout Canada. Species presence-absence data were used to calculate richness and rarity indices by tertiary watershed. Richness is higher in the southern parts of Canada, whereas rarity is concentrated in a "ring of rarity" around the periphery of the country. Environmental and stress indices were developed for each watershed using readily available mapped information. The environmental index was estimated using growing degree-days above 5degreesC, elevation range (m) within the watershed, mean annual sunshine hours, and mean annual vapour pressure (kPa). The number of crop farms, forestry, waste management, and petroleum refining facilities, road density (km-1000 km(-2)), dwelling density, and discharge sites (chimneys and laundry outlets) per 1000 km 2 described the human stresses in each watershed. Conservation priority rankings were developed for the watersheds using an integrative index of the three indices. Watersheds in southern Ontario and British Columbia were ranked high because they contain the greatest biodiversity and the most stress. This study indicates how regional analyses can guide fisheries and watershed management.