A freshwater predator hit twice by the effects of warming across trophic levels.

Many ecological responses to climate change have been documented. However, due to indirect effects, some responses can be complex and difficult to predict. For example, our understanding of effects on consumers involving responses on several trophic levels is limited. Here, combining the knowledge of trophic interactions in the EU's fourth largest lake with long-term climate and catch data, we analyse potential drivers of change in this system's apex predator. We show that warm winters correlate with later poor catches of great Arctic charr (Salvelinus umbla), and that in recent years predator-prey cycles involving this species have disappeared. The likely mechanisms are trophic mismatches directly and indirectly affecting two stages of charr, the fry and the juveniles, respectively. Our study illustrates how a long-lived consumer may be subjected to double jeopardy from the effects of warming across trophic levels, and that a food web approach can aid in disentangling the chain of mechanisms responsible.