Long distance swimmers in warming waters: Active transport in postlarval American lobsters (Homarus americanus) in the context of climate change in the Gulf of Maine

Recent declines in American lobster (Homarus americanus) settlement in the Gulf of Maine (GoM) have raised questions concerning the effects of climate change on lobster recruitment. Postlarval lobsters are strong swimmers that typically transit to inshore settlement habitats, an energy-intensive process that may be a metabolic bottleneck. Using 72-hr laboratory swimming challenges, we tested the performance of laboratory-reared postlarvae at historically favorable temperatures (15°C), as well as projected end-of-century GoM temperatures (22°C) to determine if increased water temperatures may impair the swimming abilities needed to reach settlement habitats. Video observation and analysis revealed that postlarvae in the 22°C treatment spent 25 % less time actively swimming compared with postlarvae at 15°C. Postlarvae in the 22°C swimming trials also had lower lipid content after the swimming challenge when compared with pre-trial controls; however, dry weight and protein content were not significantly different between the treatment groups. When sequential trials were run using postlarvae from the same clutch, dry weights increased with time since metamorphosis. Metabolic rates for lobsters increase in warmer temperatures, so it is possible that decreased swimming at warmer temperatures may be an adaptive strategy for energy conservation in less favorable, thermally stressful, conditions. Overall, decreased swimming activity in warmer waters may be a contributing factor in shifting patterns of lobster recruitment in the GoM.