Date of Award

Spring 1999

Project Type


Program or Major


Degree Name

Doctor of Philosophy

First Advisor

Winsor Watson


Temperature has a pervasive influence on lobster behavior, physiology and ecology and affects their subsequent distribution in thermally variable habitats such as estuaries and coastal areas. A multidisciplinary approach, including field and laboratory studies, was used to show: (1) that lobsters sense temperature with warm and cool thresholds as small as 0.1--0.2°C; (2) the relationship between temperature and activity is not linear, but instead switches between a high activity level in warmer months (10--20°C) and a lower level in colder months (<10°C) with transition periods in the spring and fall; (3) Parallel studies in the lab and field show that daily levels of activity are not greatly influenced by small temperature variations (i.e. tidally induced changes of 14°C), but activity levels are significantly higher in the field (249 +/- 55.1 m/d) than in the laboratory (88 +/- 12.0 m/d); (4) lobsters prefer a narrow range of temperatures over others available in a thermal gradient and avoid temperatures >23.5 +/- 0.4°C, suggesting that they behaviorally thermoregulate. While this preferred temperature shifts seasonally, the final preferred temperature (FPT) remains at 15.9°C. Finally, at certain temperatures, males prefer warmer temperatures than females.

The degree of thermosensitivity and responsiveness observed in these studies appears sufficient to guide thermally directed movements in the field. These thermally-influenced movements may ultimately contribute to patterns of distribution and abundance, and affect local catch rates, in thermally variable areas (e.g., male biased sex ratios in estuaries). A spatially explicit model incorporating the behaviorally determined responses to temperature described above, along with known behavioral responses to salinity, shows a significant correlation with estimates of field-derived population distributions from coastal NH and the Great Bay Estuary. Thus while temperature is not the only factor influencing seasonal movements in this system, it appears to be one of the most important factors controlling the spatial and temporal patterns of lobster distribution in estuaries, and perhaps other habitats as well.