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 triggered conjecture about negative impacts of anthropogenically induced environmental change on their long-lived planktonic larval life stages. Puerulus larvae are the critical transitional stage between pelagic larval development and coastal juvenile recruitment and may be particularly sensitive to environmental change due to immature cardiorespiratory capacity and exceptional energy demands associated with shoreward migration. We measured Sagmariasus verreauxi pueruli energy metabolism and defined their thermal tolerance, which are considered against published coastal recruitment data and spatially explicit ocean warming scenarios. The upper threshold of the thermal optimum window (upper pejus temperature range) was defined by the temperature optimum for aerobic scope. Within the upper pejus temperature range, pueruli had diminished aerobic capacity for physiological performance and used more of their finite lipid reserves to support an amplified metabolism. Sea surface temperatures at the northern extent of their natural range already reach the upper pejus range, and monitoring settlement data from the wild indicted that fewer puerulus successfully recruit during hot seasons in this area. Our study provides some evidence that physiological thermal tolerance constraints are already limiting postlarval recruitment. Predicted increases in water temperatures for their rapidly warming habitat will amplify the thermal challenge experienced by pueruli and may result in large shifts in lobster distribution and significant re-shuffling of species assemblages, creating challenges for sustainable natural resource management.