Evidence of chronic stress in winter flounder, Pleuronectes (= Pseudopleuronectes) americanus living adjacent to a pulp and paper mill in St. George's Bay, Western Newfoundland

Barker, Duane Edward (1993) Evidence of chronic stress in winter flounder, Pleuronectes (= Pseudopleuronectes) americanus living adjacent to a pulp and paper mill in St. George's Bay, Western Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

Winter flounder, Pleuronectes (= Pseudopleuronectes) americanus, living adjacent to a pulp and paper mill at Port Harmon, Stephenville, Newfoundland, were compared with flounder from a reference site, St. George's, 12 km from the mill, for signs of chronic stress. Several bioindicators of stress in fish were employed, including condition factor, organ somatic indices, haematological values, external lesions, and parasitofauna. Winter flounder from Port Harmon, (effluent site) showed significantly lower condition factors (K-factors) and hepatosomatic indices (HSI) indicative of depleted energy reserves, and physiological impairment, than those from St. George's. Delayed spawning was evident in both male and female winter flounder from Port Harmon compared with those from St. George's. Blood haemoglobin, haematocrit, and lymphocyte levels were significantly lower at Port Harmon, than in samples from St. George's. Fin necrosis of the caudal, dorsal and anal fins, was greater (in terms of prevalence and intensity) in flounder from Port Harmon. The prevalence and intensity of intestinal nematodes was significantly higher at Port Harmon, than St. George's; possibly the result of differences in diet. Conversely, the prevalence and intensity of intestinal acanthocephalans was significantly lower at Port Harmon, and was possibly related to effluent discharge. No differences were found in a comparison of prevalence and intensity of intestinal digeneans. The prevalence and severity of infection of a parasitic microsporan protozoan, Glugea stephani, and the encysted metacercaria of the digenean, Cryptocotyle lingua, were, however, significantly higher among flounder from Port Harmon. Anaemia, low lymphocyte levels, a high prevalence of fin necrosis and parasitemias (Glugea stephani, Cryptocotyle lingua) are all suggestive of immunosuppression. Since the above differences were not attributed to differences in basic water parameters (temperature, salinity, conductivity, pH, and dissolved oxygen) at the two sites, the chronic stress evident in winter flounder from Port Harmon is most likely attributed to pulp mill effluent discharged at Port Harmon.

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