15 Examination of angler-caught piscivore stomachs revealed that Lake Trout Salvelinus namaycush, Chinook Salmon Oncorhynchus tshawytscha, and Walleyes Sander vitreus altered their diets in response to unprecedented declines in Lake Huron's main-basin prey fish community. Diets varied by predator species, season, and location but were nearly always dominated numerically by some combination of Alewife Alosa pseudoharengus, Rainbow Smelt Osmerus mordax, Emerald Shiner Notropis atherinoides, Round Goby Neogobius melanostomus, or terrestrial 20 insects. Rainbow Trout Oncorhynchus mykiss (steelhead), Coho Salmon Oncorhynchus kisutch, and Atlantic Salmon Salmo salar had varied diets that reflected higher contributions of insects. Compared with an earlier (1983–1986) examination of angler-caught predator fishes from Lake Huron, the contemporary results showed an increase in consumption of nontraditional prey (including conspecifics), use of smaller prey, and an increase in insects in the diet, suggesting that piscivores were faced with chronic prey limitation during this study. The management of all 25 piscivores in Lake Huron will likely require consideration of the pervasive effects of changes in food webs, especially if prey fish remain at low levels. Freshwater piscivores have the ability to alter prey behavior (Werner and Hall 1988), structure prey communities (Zaret and Paine 1973; Mittlebach et al. 1995), and alter production 30 via top-down effects (Carpenter and Kitchell 1988). Piscivore effects have been especially strong in the Laurentian Great Lakes, where fisheries managers introduced nonnative Pacific salmon Oncorhynchus spp. during the 1960s to control Ale-wives Alosa pseudoharengus and consume Rainbow Smelt 35 Osmerus mordax (Kocik and Jones 1999; Tanner and Tody 2002), both nonnative planktivores (Aron and Smith 1971).