Long-Term Changes in the Diet of Northern Pike in a Changing Environment

Northern pike (Esox lucius) is a key and flexible piscivore in many fresh waters of the northern temperate zone, but few studies have examined its diet in response to long-term changes in environmental conditions. Here, we describe the winter diet from 1976 to 2009 of pike in the lake of Windermere, U.K., where climate change, eutrophication and species introductions have induced fundamental changes in the fish community. Approximately 98% of prey identifiable to species comprised native Arctic charr (Salvelinus alpinus), brown trout (Salmo trutta), Eurasian perch (Perca fluviatilis) and pike and non-native roach (Rutilus rutilus). Over the study period, the dietary importance of salmonids decreased, while that of percids, esocids and particularly cyprinids increased. In the 1970s, Arctic charr and brown trout comprised 94% of the diet but in the 2000s these two species accounted for just 55% with perch and roach comprising 41%. The recent changes observed in the Windermere fish community of a decrease in native salmonids and an increase in cyprinids are consistent with the generally expected effects of climate change. Here, we have shown that they have led to corresponding changes in pike diet which, in turn, have implications for the lake’s food web structure.