Parasites of winter flounder (Pleuronectes americanus) as an additional bioindicator of stress-related exposure to untreated pulp and paper mill effluent: a 5-year field study.

A study was conducted in a marine inlet to assess the effects of untreated discharges from a pulp and paper mill, a municipality, and industries in western Newfoundland on winter flounder (Pleuronectes americanus), a fish species shown previously to be sensitive to environmental contaminants in sediment. The fish were captured by SCUBA divers about 2 km down-current from the mill discharging effluent containing resin acids, and at three reference sites 2 to 11 km away near the opposite shore, each spring in five consecutive years and the fish were necropsied on site. A total of 360 and 339 flounder were examined near the mill and references sites, respectively. Several bioindicators were used to assess fish health including parasites. More fish exhibiting external and microscopic lesions in several tissues, lower condition factors, elevated hepatosomatic index, and delayed reproductive development were observed in samples taken near the paper mill than at the reference sites. A higher prevalence of an ectoparasite, Cryptocotyle lingua, but a significantly lower mean abundance of three metazoans infecting the digestive tract was noted in fish near the mill than in the reference samples. These results, comprising abnormal fish size distribution, low body condition factor, external and internal lesions, enlarged liver, delayed gonadal development, and changes in parasitism, were stress-related, indicative of impaired health, and associated primarily with untreated discharges from the pulp and paper mill. This integrated and multidisciplinary study also provides further evidence on the use of fish parasites as a valid and an additional bioindicator in programs monitoring environmental contaminants.