Impact of logging and natural fires on fish communities of Laurentian Shield lakes

The goal of this study was to determine if natural fires and logging have a significant impact on abundance, growth, and size structure of fish popula tions in 38 lakes of the Laurentian Shield (Quebec, Canada). The watersheds of nine of these lakes underwent logging and nine underwent natural fires, while the 20 remaining lakes were used as references. No significant diffe rences were found among the three lake groups in the catch per unit of effo rt of the most abundant species: white sucker (Catostomus commersoni), nort hern pike (Esox lucius), yellow perch (Perca flavescens), lake whitefish (C oregonus clupeaformis), fallfish (Semotilus corporalis), brook trout (Salve linus fontinalis), walleye (Stizostedion vitreum), and burbot (Lota lota). No significant difference was found among control, burned, and logged lakes in the back-calculated length of yellow perch, for which age determination s were made. However, we found that the proportions of small yellow perch a nd white sucker were significantly lower in populations of impacted lakes ( burned and logged lakes pooled). The influence of logging and fires remaine d significant when a series of biotic and abiotic variables on watershed an d lake characteristics were accounted for in multiple regression analyses. The lower proportion of small fish in impacted lakes could be due to an inc rease in postemergence mortality or to a shift of individuals to the pelagi c zone.