Trout Do Not Cope Well to Extreme Environmental Conditions or Do They?

Recent warming of terrestrial climates around the world has motivated concern about consequent alteration of riverine ecosystems. Increasing evidence in the literature suggests that future environmental regimes may not simply be predicted by a monotonic change of average conditions. Instead, changes in the frequency and variability of extremes events are expected. How will the stability and persistence of fish populations be affected by such type of changes? Here, we explore the role of varying natural fluctuations of environmental regimes on the stability of stream-trout populations. Using an individual-based model, we changed the variability of flow and temperature in streams, but kept similar average conditions. Under conditions of stream temperature that did not exceed trout physiological limits, preliminary results show population responses to variation in a major constraint of summer habitat (i.e., baseflow). In winter, trout were constrained by high flow and they had reduced growth under colder conditions. Our mechanistic modelling approach demonstrates how sensitive populations are to hydroclimatic extremes across seasons, which provides insights to successful ecological forecasting. This has important conservation implications given the risk of local extinctions may increase due to expected global environmental change.