Post-Impoundment Changes to the Speed River Fish Assemblage

Abstract

Changes to the Speed River fish assemblage were investigated 27 years after the creation of the Guelph Lake reservoir. Electro-fishing and seine haul data collected during 2003 were compared to pre- (1975) and post-impoundment (1976 and 1978) surveys. Since its creation, the Guelph Lake fish assemblage has predictably shifted from one dominated by fluvial specialists (fantail darter and creek chub) to one dominated by habitat generalists common to lakes and reservoirs (bluntnose minnow, pumpkinseed sunfish and black crappie). Since 1975, species richness and diversity have increased at un-impounded sites along the Speed River. The occurrence of new species in Guelph Lake and upstream along the Speed River is attributed to the stocking of non-native species. Reductions in the distribution and abundance of certain fluvial specialists (fantail darter and northern hogsucker) are attributed to the flooding of riverine habitat and changes to downstream habitat conditions. Observed long-term changes to fish assemblage were not evident from earlier post-impoundment surveys.