Nearshore fish assemblages associated with introduced predatory fishes in lakes

1. Changes to native fish assemblages in lakes are commonly associated with introduced predatory fishes. How fish assemblages change as multiple predatory species are introduced is not well understood. 2. This study investigated the relationship between the presence of introduced large-bodied predatory fishes (largemouth bass Micropterus salmoides, pike Esox lucius, rock bass Ambloplites rupestris, smallmouth bass Micropterus dolomieu, walleye Sander vitreus) and the composition of native fish assemblages in littoral areas of 40 lakes in Algonquin Provincial Park, Ontario, Canada. Fish assemblages were compared across lakes of different predator composition, and within lakes before and after recent predator invasions. 3. The presence of an introduced predator was associated with significantly different native fish assemblages across lakes, after controlling for environmental and spatial variables. 4. Native fish assemblages did not significantly vary across lakes with more than one predator species. Furthermore, while declines in native species richness over time were observed in a number of lakes, these were not associated with introductions of additional predators. 5. Several small-bodied species (brook stickleback Culea inconstans, fathead minnow Pimephales promelas, finescale dace Chrosomus neogaeus, and northern redbelly dace Chrosomus eos) consistently showed strong negative correlations with predator presence. 6. The results suggest that predatory fish introductions alter native fish assemblages and that this impact is consistent regardless of the number of predatory species introduced. Copyright (C) 2011 John Wiley & Sons, Ltd and Her Majesty the Queen in Right of Canada.