Alteration of Fish Communities in Lakes Stressed by Acid Deposition and Heavy Metals near Wawa, Ontario

Abstract

Based on chemical criteria such as excess sulfate and low bicarbonate relative to cation, 50 lakes in the Wawa area show some degree of acidification. We conclude that the observed perturbations of lake chemistry and fish populations were primarily the result of smelting operations in the Wawa area. Six lakes have acidified to pH 3.1–4.1 and had high concentrations of metals such as Al, Mn, and Fe. Most of the lakes were in contact with felsic and mafic metavolcanic rocks containing minerals such as siderite, and only a few lakes had granitic basins. The six most acidic lakes contained no fishes and some lakes in the fume-kill area had known losses of brook trout (Salvelinus fontinalis) and lake trout (Salvelinus namaycush) populations. Based on a regression of number of species on lake area for 34 lakes, it was estimated that 83 fish populations have been lost from 16 lakes. Fish community changes were difficult to assess due to the distributions of species in the four watersheds. The northern pike (Esox lucius)–walleye (Stizostedion vitreum vitreum)–yellow perch (Perca flavescens) community was found now to be present only in lakes distant from the source of emissions. The fish community with brook and/or lake trout as the top predator was the most affected.