Evidence of fish population responses to acidification in the Eastern United States

The hypothesis that acidification has reduced or eliminated fish populations in certain areas of the eastern United States was investigated by examining present and historical fishery survey records. The causes of acidification (e.g., atmospheric deposition) were not specifically considered, although instances of obvious alternative explanations (e.g., acid mine drainage, organic acids) were avoided. The number of usable data sets located was small. Trend analyses are severely limited by the lack of high quality historical data. The strongest evidence for fisheries declines associated with acidification is provided by data for the Adirondack Mountain region of New York. In some lakes, fish populations have declined or disappeared; lakes experiencing fishery declines are now acidic. Alternative explanations for changes in fish communities over time were examined. In 49 lakes, some or all fish populations have apparently been lost with no available explanation other than acidification. Extrapolation of these data to the entire Adirondack Mountain region suggests that perhaps 200 to 400 lakes may have lost fish populations as a result of acidification. Streams in Pennsylvania and Massachusetts also had documented declines in fish populations that were associated with acidity; however, the data are fewer and less complete than those for New York. Acidification effects on fishery resources in other regions of the eastern United States are apparently minimal. The extent of the damage to date appears small relative to the total resource.