Fish Species Richness in Relation to Lake Area, pH, and Other Abiotic Factors in Ontario Lakes

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Abstract
Survey data from 2931 Ontario lakes were analyzed to determine how fish species richness was empirically related to a set of 19 physical and chemical limnological variables. Lake area was the dominant factor, explaining 18% of the variation in species number. Total aluminum, latitude, dissolved organic carbon, and elevation together explained an additional 16%. The strong relationship between species number and lakes area was quantified using lakes with pH .gtoreq. 6.4 and then applied to all the surveyed lakes to estimate species number. Deviations from the expected values indicated that species number decreased with decreasing pH below 6.0, resulting in significantly fewer species in lakes with pH alone explained 21% of the variation in species number; elevation, lake area, and dissolved organic carbon together explained an additional 20%. Interactions between pH and lake area were identified; lake size decreased significantly both at low pH (< 6.8) and at high pH .gtoreq. 7.7). An understanding of these interactions was essential in explaining the relative roles of pH and lake area in determining species richness.