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Massachusetts Bay: Winter Flounder Monitoring
At most stations, incidence of fin erosion, a condition that can be indicative of elevated concentrations of ammonium and other pollutants, was lower than was observed in 2007. Prevalence of fin erosion has varied in recent years, with no clear evidence of short-term trends. Over a longer period, since the late 1970s and early 1980s, the incidence and severity of fin erosion has lessened considerably. Blind-side ulcers, which were first detected in 2003, were uncommon, continuing an ongoing decline. Ulcers were present in only 2% of fish sampled near the outfall; at the peak of the infection in 2004, 36% of the fish had ulcers. The flounder livers are tested for levels of lead, mercury, cadmium, copper, nickel, silver, zinc, chromium, PAHs, PCBs, DDT, and ten other pesticides. In order to test for potential human health effects, mercury, PCBs, DDT, and seven other pesticides are also measured in the edible flounder fillets. For many fish species, consumption advisories because of mercury are a concern. However, mercury levels in winter flounder have been stable at about 50-100 parts per billion, well below the U. S. Food and Drug Administration (FDA) limit of 1,000 parts per billion. Levels of PCBs and DDT are also well below FDA limits. PCBs, DDT, and mercury in fillet of flounder caught in the harbor have fluctuated between years with no clear pattern. All these chemicals have measured well below the FDA action limits. Liver disease in winter flounder is a sensitive indicator of pollution effects because the liver can be damaged as contaminants are metabolized. The incidence of centrotubular hydropic vacuolation (CHV), a mild condition associated with exposure to contaminants, remained low. Incidence of CHV in fish from the outfall site continued to be lower than it had been in the years before the Massachusetts Bay outfall began to discharge. Incidence of CHV at Deer Island Flats has also declined since the bay outfall started up.
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