Quantifying impacts of pulp mill effluent on fish in Canadian marine and estuarine environments: problems and progress

Amendments to the federal Pulp and Paper Effluent Regulation's in effect since 1992, require mills in Canada discharging effluent to an aquatic receiving environment to conduct an Environmental Effects Monitoring (EEM) Program to determine whether existing regulations adequately protect fish, fish habitat and use of fisheries resources. As one component of the EEM, mills measure indices of growth, survival and reproduction in wild-caught fish exposed to effluent and compare them with fish not exposed to effluent. A review of the first round of Fish Surveys (Cycle 1: 1993-1996) indicated that they contributed useful data in the freshwater receiving environments for which they had been designed, but performed poorly in the more complex marine and estuarine environments. The most prevalent and serious problems were that insufficient fish were caught and the degree of exposure to effluent could not be quantified. Recommendations to address these problems in Cycle 2 (1997-2000) included selection of small-bodied, presumably more sedentary, fish and studies on the alternative approaches: caged bivalves and onshore bioassays (mesocosms). Difficulties encountered in Cycle 1 studies which could not be resolved became reasons to exclude the Fish Survey from 12 of 28 marine EEM studies in Cycle 2. Six marine mills completed the standard Fish Survey with finfish. Three of these used small-bodied fish successfully, though further information will be required on their range of movement and technical guidance on appropriate sampling. Six studies examined wild bivalves or snails in place of one or both finfish sentinels. None of the invertebrate studies provided all of the information required by the Fish Survey, with only two studies providing age information required to assess growth, only one study reporting gender, and none of the studies reporting measures of reproduction. Six mills conducted or participated in developing alternative approaches for fish surveys: two caged bivalve studies, three mesocosm studies using fish, and one onshore bioassay using bivalves. While providing no direct measurements of effects on reproduction these tools evaluated potential impacts of effluent on survival and growth and supplied information helpful for subsequent investigations of the causes of effects observed in wild fish.