Research Document 2017/042

Monitoring to determine the efficacy of utilizing fishless lakes as fish habitat compensation in Labrador

By Roberge, M.M., and Warren, T.N.

Abstract

This paper reports on methods for assessing the effectiveness of fish habitat-related measures implemented as part of the regulatory approval for two mining projects in Newfoundland and Labrador. Between 2003 and 2004 works or undertakings associated with two mining projects one in western Labrador and another in northern Labrador resulted in the loss of lacustrine habitats. To compensate for these losses, the transfer of fish from the impacted lakes into fishless lakes located within their respective watersheds was proposed and subsequently authorized under the Fisheries Act. After the fish transfers, monitoring programs were required to determine whether there was sustainability of the transferred fish populations. Methods used to determine population sustainability included such things as visual surveys along the shoreline, outlets and into tributaries; electrofishing to determine recruitment success; mark-recapture studies to estimate population size; and collection of various morphometrics to evaluate fish population status/health. At one location an outlet stream was also created to provide for spawning and rearing habitats. Monitoring to determine effectiveness of the created outlet included surveys to assess habitat features, including wetted width, depth, shape, bank height, water discharge/velocity (high, medium, low flows) and habitat utilization (visual and electrofishing surveys).

An evaluation of the above metrics has been conducted, which revealed that most metrics utilized were useful, especially when used in conjunction with others. The metrics were successful in identifying changes over time and have enabled the assessment of the status of the compensation and determine whether additional changes were required in order for the compensation to function more effectively. The only metric that was determined to be ineffective was the use of visual surveys for redds. When assessing compensation, metrics should be collected over a sufficient time period, be used in conjunction with other metrics, and should be detailed enough to provide a clear picture of trends. Baseline data is also critical when using fishless lakes as a compensation option as the lake must be determined to be fishless, as well as provide a suitable environment for the transferred populations to survive and successfully reproduce.

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