| Introduced predators can have strong negative effects on native prey populations; the severity of this impact can be greater than that of native predators and can change with multiple predator introductions. I examined relationships between native fish assemblages and five widely introduced piscivorous fishes: largemouth bass Micropterus salmoides, northern pike Esox lucius, rock bass Ambloplites rupestris, smallmouth bass Micropterus dolomieu and walleye Sander vitreus . Analysis of data from over 9000 lakes in Ontario, Canada, revealed that the presence of these piscivores reduces prey species richness, and that the magnitude of this impact varies with predator species and predator richness. There was no difference in the effects of introduced and native smallmouth bass populations on prey richness. Results from a multi-lake field study at Algonquin Park (Ontario) suggested predators structure nearshore fish assemblages, although to a lesser degree than spatial and environmental factors. There was little evidence that fish assemblages change through space and time with increased predator richness, implying functional redundancy of later invaders. |
