Characterizing thermoregulatory trade-off behavior in juvenile American lobster, Homarus americanus

Nielsen, Travis Vagn James (2015) Characterizing thermoregulatory trade-off behavior in juvenile American lobster, Homarus americanus. Masters thesis, Memorial University of Newfoundland.

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Abstract

The American lobster, Homarus americanus, forms an important fishery in Atlantic Canada and New England. As such, a plethora of information exists on the biology of the larval dispersal phases, as well as that of the adult lobster. However, comparatively less is known about the behaviour and physiology of the juvenile stages. The juvenile phase is a critical period of life, characterized by high levels of mortality. As a result, population parameters such as abundance and distribution can be significantly influenced by events occurring during the juvenile phase. Newfoundland is the northern most range limit for H. americanus, and associated low temperatures may affect foraging and sheltering behaviours. Laboratory experiments showed that juveniles preferred temperatures of ~18°C and were most active between 10-20°C. Heat stroke occurred above 30°C, while basal activity stopped at ~2.0°C and reactions to sensory stimuli ceased at ~-1°C. Although juvenile lobsters preferred water of 18ﾟC, they would choose thermal regimes below their preference range if shelter or food was available. When shelter was present, the juveniles increased activity levels to maintain the shelter. Because juveniles are vulnerable to predation the acquisition of shelter appeared to override both thermal preferences and foraging behaviour. Although shelter may protect against predation, the use of sub-optimal thermal habitats will influence metabolism and reduce potential for growth in juvenile lobsters.

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