The importance of activity metabolism in understanding bioenergetics of free ranging snow crab (Chionoecetes opilio)

Improving our understanding of activity budgets in marine animals is critical to calibrating and refining bioenergetic models to predict larger-scale population trends and distributional shifts with climate change. Lab studies have been instrumental in identifying environmental influences on metabolism, particularly for commercially important species like snow crab ( Chionoecetes opilio ). However, extrapolating laboratory results to free-ranging organisms carries the risk of generating misleading interpretations, particularly for metabolic processes such as activity that emerge from multifaceted and context-specific mechanisms. We combined laboratory-derived energetic equations with telemetry data analyzed using Hidden Markov Models to estimate total in-situ standard and activity-related metabolic demand for snow crab living in Cabot Strait and the Grand Banks, regions that together encompass nearly the full range of the species' thermal distribution in Atlantic Canada. We compare these field estimates of metabolic demand to previously published studies to understand which components of metabolism are most important across sites and whether behavioral changes in activity compensate for increased metabolic costs at higher temperatures. Our study illustrates that thermal effects on standard metabolism is not a dominant driver of overall snow crab metabolism within the range of our observations, in contrast to lab studies. Instead, we observed active metabolism to be a more important contributor to total metabolism, and variation in movement patterns across study areas resulted in a moderating effect on lab-derived expectations of temperature on overall metabolism. • Hidden Markov Models were applied to better understand activity metabolism of free ranging snow crab. • Thermal effects on standard metabolism did not dominate wild snow crab metabolism across the broad thermal distribution studied. • Active metabolism was the most important contributor to total metabolism. • Thermal effects on realized activity metabolism were moderated by changes in movement patterns across study areas.