Standard Talk (15 mins) Australian Society for Fish Biology Conference 2022

Going with the flow (and the heat): Growth of brown trout (Salmo trutta) along thermal and hydrological gradients (#9)

Patricia Koh 1 , John Morrongiello 1 , Matt West 1
  1. University of Melbourne, Brunswick, VIC, Australia

Australia’s naturally variable environment is projected to become more extreme and unpredictable with human-induced climate change. In south-eastern Australia, declining rainfall and warming temperatures driven by climate change threaten freshwater species. Coldwater fish are particularly vulnerable as changing environmental conditions reduce the amount of suitable habitat and shift their ranges to higher elevations. Understanding how coldwater fish respond to variable environmental conditions is critical for determining the viability of populations in a warmer and drier future. This knowledge is especially important for species that form economically and culturally important recreational fisheries.

We examined how the environment such as fluctuations in temperature and hydrological flow can influence somatic growth in a non-native coldwater species, brown trout (Salmo trutta). Otoliths were collected from brown trout across 14 wild populations in Victoria, encompassing a range of climatic and hydrological conditions. We used these otoliths to create growth biochronologies to model the growth dynamics of trout with temperature and river flow as key variables. We found that there were spatial and temporal differences in growth rates and that these were modulated by hydrology and climatic variables. Our findings indicate that the growth of brown trout is not robust to environmental variation suggesting reduced resistance and resilience to predicted future climate change scenarios.