Evaluating the Applicability of an Ontario Standard for Monitoring Fish Populations in the Subarctic

The Ontario Ministry of Natural Resources Broadscale Fish Community Monitoring (BsM) gillnetting protocol was selected as per regulatory requirements to assess the potential effects of a diamond mine on the fish community of a 1600 ha subarctic lake exposed to effluent. The program is intended to provide an assessment of the entire fish community.  In 2013, gill nets were set on the diamond mine lake as well as two reference lakes to compare fish community composition and abundance among lakes, while also investigating the efficacy of BsM in Canada’s north. A Lake Trout mark-recapture program was conducted concurrently on the diamond mine lake to estimate population numbers. The BsM method did not capture all species present in each lake. The abundance of Lake Trout in all three lakes ranged from 2 to 6-fold higher than the mean for 275 Ontario lakes, despite a low mark-recapture estimate (1.14 trout/Ha).  Lake Trout may be more active and vulnerable to gillnets at this latitude, and these inconsistent estimates may be due to specific ecological differences between Ontario and NWT fisheries.  These results emphasize the need to establish local, comparable reference conditions when using standard protocols designed for different ecoregions.