Behavioral thermoregulation of ovigerous American lobsters (Homarus americanus)

Ectotherms, including American lobsters (Homarus americanus), can modify their body temperature using behavioral thermoregulation, by moving to areas closer to their preferred temperature. To better understand the potential consequences of climate change on lobster reproduction and recruitment, we measured the thermal preferences and locomotor activity of adult female lobsters that were carrying eggs (ovigerous; n = 139), or not (n = 143), in a thermal gradient tank with a temperature range of 6–20 °C. Trials were carried out year-round so that we could compare the thermal preferences of ovigerous lobsters carrying eggs at varying developmental stages and determine if ambient water temperatures influenced their preferred temperatures. Seasonal temperature preferences were similar for both ovigerous and non-ovigerous females with cooler temperatures preferred in the fall and winter, and warmer temperatures during the summer. However, in general, females with newly extruded eggs preferred temperatures warmer than our model predicted for all females combined, while those with eggs that were very close to hatching preferred cooler temperatures than predicted. While there were no significant differences in the relative activity of females with or without eggs, females with eggs that were hatching tended to move more. These findings demonstrate that seasonally changing water temperatures have a large impact on the thermal preferences of American lobsters, while the developmental stage of their eggs also plays a role in temperature preferences. These data should be taken into account when assessing the potential impact of warming oceans on the distribution of lobsters in the Gulf of Maine.