Thermal tolerance of the nektonic puerulus stage of spiny lobsters and implications of ocean warming

Recent recruitment declines in important spiny lobster fisheries worldwide have triggeredconjecture about negative impacts of anthropogenically induced environmental change ontheir long-lived planktonic larval life stages. Puerulus larvae are the critical transitional stagebetween pelagic larval development and coastal juvenile recruitment and may be particularlysensitive to environmental change due to immature cardiorespiratory capacity and exceptionalenergy demands associated with shoreward migration. We measured Sagmariasus verreauxipueruli energy metabolism and defined their thermal tolerance, which are considered againstpublished coastal recruitment data and spatially explicit ocean warming scenarios. The upperthreshold of the thermal optimum window (upper pejus temperature range) was defined by thetemperature optimum for aerobic scope. Within the upper pejus temperature range, pueruli haddiminished aerobic capacity for physiological performance and used more of their finite lipidreserves to support an amplified metabolism. Sea surface temperatures at the northern extent oftheir natural range already reach the upper pejus range, and monitoring settlement data from thewild indicted that fewer puerulus successfully recruit during hot seasons in this area. Our studyprovides some evidence that physiological thermal tolerance constraints are already limiting postlarvalrecruitment. Predicted increases in water temperatures for their rapidly warming habitatwill amplify the thermal challenge experienced by pueruli and may result in large shifts in lobsterdistribution and significant re-shuffling of species assemblages, creating challenges for sustainablenatural resource management.