Assessing Fish Community Structure in Relation to Water Quality in a Small Estuarine Stream Receiving Oil Refinery Effluent

A large oil refinery discharges its effluent into Little River, a small estuarine stream entering Saint John Harbour, New Brunswick, Canada. An effects-based approach was used to assess the potential responses of fish and fish habitat to the effluent from the oil refinery. The study included a fish community survey and a water quality survey. Lower abundance, species richness, and biodiversity, as well as increased frequency of empty minnow traps, were found downstream of the effluent discharge. Water quality surveys demonstrated that the receiving environment is subjected to extended periods of low dissolved oxygen levels downstream of the effluent discharge. The anoxic periods correlated with the discharge of ballast water through the waste treatment system.