We ran a mesocosm experiment using the non-indigenous mud crab Rhithropanopeus harrisii, which has entered the underwater environments of the Åland Islands in recent years. Our research aimed to explore the significance of food preferences under the stress from increasing water temperatures to identify potential shifts in ecological dynamics. The mud crab was offered various combinations of local benthic prey species, including Gammarus spp., Mytilus trossulus, and Theodoxus fluviatilis, to observe their performance functions (survival) as well as their predator-prey interactions (feeding rates) under changing thermal conditions, from 12 to 40°C, for 8 days.