Do Climate-Mediated Effects on Adult Size Affect Larval Lobster Performance?

Recent research reveals that as the Gulf of Maine warms, female American lobster (Homarus americanus) are maturing at significantly smaller sizes. Aside from the lower fecundity associated with smaller adult size, we hypothesize that small females may not invest as much energy per larva as large females, thereby compromising post-hatch performance and survival. Alternatively, reproductive output could be greater if smaller, earlier maturing, mothers have more opportunities to spawn over their life time, assuming their larvae perform as well as those from larger mothers. In a two-factor experimental design, we evaluated maternal size effects under two feeding regimes, one with and the other without planktonic food. In the starved treatment we measured larval weight change and respiration rate over 5 days. We found that larvae from large mothers lost weight significantly faster, yet maintained significantly higher mass-adjusted respiration rates after 5 days. In the food saturated treatment larval stages I and II from large mothers were significantly larger and weighed more than those from small mothers. Larvae from small mothers developed significantly more slowly, and did not develop beyond stage II during the course of this experiment. These preliminary results warrant further evaluation of the impact of maternal size on larval performance. Our results may have long-term implications for effects of climate warming on the reproductive performance and recruitment success of this iconic species, and in turn for the many Gulf of Maine coastal communities that depend on the fishery it supports.