Evaluation of an in situ early life stage test with cutthroat trout, Oncorhynchus clarki, for environmental monitoring – a case study using mine effluent

Abstract

This study evaluated an in situ early life stage test using cutthroat trout for potential use in Canada's Metal Mines Effluent Regulations' Environmental Effects Monitoring (EEM) program. Current field monitoring approaches focus on either adult fish surveys or mesocosm studies, but both of these have inherent limitations that may affect their suitability on a site-specific basis. This study evaluated an alternative approach, namely an in situ toxicity test, as part of an EEM program for a zinc, copper and gold mine. Hatchboxes containing cutthroat trout embryos were placed in a creek that receives treated effluent from the mine, and monitored through the swim-up stage to evaluate hatching success, survival, normal development and growth. Advantages of the method include: no feeding requirement during exposure, fixed exposure locations, relevant endpoints and high statistical sensitivity. In addition, the extended exposure period integrated long-term exposure variables, including low-flow and freshet events. This approach also has application to other salmonid species and types of discharges.