Mercury is an element that occurs naturally in low concentrations in air, water, soil and in plant and animal matter. At one time mercury was widely used in industry. Direct discharges of mercury from major industrial sources into rivers and lakes have been virtually eliminated, although residual contamination may still exist in some locations. Industrial and other activities associated with the burning of fossil fuels are major sources of mercury today. Significant quantities of mercury enter the aquatic environment of the Moose River Basin from the atmosphere from both man-made and natural sources. Scientific evidence indicates that long-term flooding following construction of reservoirs accelerates the release of mercury into the water. When the concentration of mercury becomes high enough, it can be harmful to living organisms, including humans. Mercury is present in waters of the Moose-River Basin in several forms. An organic form known as methylmercury is easily absorbed by fish directly through their gills or indirectly from their diet. Since lake sturgeon have a long lifespan, their bodies can accumulate high levels of methylmercury over time. Larger, older lake sturgeon tend to have higher concentrations of mercury than smaller, younger ones. Fish in the northern part of the basin tend to have higher mercury concentrations than those in central locations.
There are contaminants in fish other than mercury that can affect human health. Advice on safe fish consumption can be found in the Guide to Eating Ontario Sport Fish available at government and retail outlets or at ontario.ca/fishguide.
Mercury body burdens for lake sturgeon in rivers of the Moose River Basin
Previous page... Current state of the resource | Next page... Factors influencing lake sturgeon populations
