THE OCCURRENCE OF CYPRINIDAE AND OTHER SMALL FISH SPECIES IN RELATION TO PH IN ONTARIO LAKES

We used data from 426 Ontario lakes to determine how the number of fish species in a lake was empirically related to lake area and pH. In lakes of pH 6.0 and above, the total number of species increased with lake area, whereas the number of cyprinid species was generally unrelated to lake size. As a result, the fraction of cyprinid species in the total species count decreased with increasing lake size. When these effects of lake size were taken into account, the total number of species, the total number of cyprinid species, and the cyprinid fraction all decreased below pH 6.0. We used an augmented set of 488 lakes to evaluate 13 common small (less-than-or-equal-to 10 cm total length) fish species as potential early indicators of changes in the fish community due to acidification. The most promising indicator species were fathead minnow Pimephales promelas, common shiner Notropis cornutus, bluntnose minnow Pimephales notatus, blacknose shiner Notropis heterolepis, and slimy sculpin Cottus cognatus.