Date of Award

Fall 12-9-2016

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)


Marine Biology


Heather Hamlin

Second Committee Member

Robert Bayer

Third Committee Member

Ian Bricknell


The American lobster (Homarus americanus, Milne-Edwards, 1837) is part of a multi-billion dollar fishery and is essential to Maine’s economy. With warming waters in the Gulf of Maine and declines in the lobster stock in Southern New England, it is important to examine the impacts of temperature on larval lobsters. Lobster larvae were reared at four nominal temperatures (14°C, 16°C, 18°C, and 22°C) based on the temperature regimes observed in Northern Maine (NME), Southern Maine (SME), and Southern New England (SNE). Mortality and timing to each stage of larval development were examined for each temperature. Total hemocyte counts were examined to assess how temperature may impact immune function and health of larval lobsters. The carapace of the larvae was examined using scanning electron microscopy (SEM) to assess for differences in cuticle thickness, which is a factor associated with the ability of lobsters to resist colonization of disease causing bacteria. It was found that larval survival increases and larval development time decreases with higher temperatures. Total hemocyte counts were significantly higher in larvae reared at 22°C than at 18°C, which indicates that larvae were approaching their thermal threshold and becoming stressed at 22°C. There was no significant difference in the cuticle thickness of larvae reared at various temperatures. Overall, it appears that larvae exhibit optimal development and survival at temperatures higher than previously thought. This information may explain the increase in lobster landings within the Gulf of Maine and is beneficial to hatcheries looking to improve survival and accelerate development time. Hemocyte abundance was altered by temperature in stage IV larvae and could therefore serve as a beneficial metric of thermal stress.