Effects of warming on the interactions between fish species
A warmer climate allows warm adapted species like perch, pike and roach to colonize cold lakes. In this project we study how invasion by these species affect resident species like brown trout, Arctic char, grayling and whitefish.
Climate warming have direct effects on the outcome of species interactions because different species prefer different temperatures. Warming also leads to different indirect effects. A particularly important indirect effect is the increased transport of brown humic substances from terrestrial to aquatic systems. This brownification affects the feeding efficiency of visually feeding fish species but it also have effects on the physical and chemical environment, such as mixing conditions and oxygen concentrations.
In this project we use empirical data to build models of coexistence niches, which describes under what conditions fish species can coexist. For example, we have shown the brown trout only coexist with pike in lakes that are large, unless they are very cold. We are now building models of the coexistence niche for pike and Arctic char. Here we find that Arctic char only coexist with pike in deep, cold and clear lakes.