Personality Predicts Success at Using Thermal Refugia in Brook Trout (Salvelinus fontinalis)

Elaine Langone Center, Terrace Room

Climate change is one of the most pervasive threats to coldwater fish populations, and there remains considerable uncertainty as to how organisms will respond to changes in local environmental conditions. For brook trout (Salvelinus fontinalis), a species of coldwater fish with important socioeconomic and ecologic value, climate change is expected to reduce available habitat by as much as 80%. However, models predicting range shifts are conducted at large spatial scales and fail to account for local habitat features that enable population persistence. Small areas of thermal refugia created by groundwater upwelling or tributary confluences can decrease water temperature by up to 10°C, and have been shown to increase trout survival. However, individual fish survival depends on the individual’s ability to locate and compete with other fish for access to thermal refugia. In this study, we investigated how fish size and behavior influence an individual’s success at finding and competing for food and space in a thermally diverse environment. After assessing behavioral phenotype, 20 brook trout were randomly assigned to each of four artificial streams. We increased ambient stream temperature from 14ᵒC to 23ᵒC over seven days while maintaining one pool at 14ᵒC to simulate groundwater upwelling. During trials, movement was monitored via two PIT tag antenna arrays, and agonistic interactions were documented by scoring underwater videos filmed four times a day. Overall, most fish moved less and engaged in more competitive interaction at higher temperatures. However, there was significant individual variation in movement, with some individuals moving more in warmer temperatures, presumably to access food. Competitive dominance was only weakly correlated to size. These results suggest that individual fish respond differently to stream temperature rise, and that certain behavioral phenotypes may be more successful at finding and occupying thermal refuge.