The American lobster, Homarus americanus, is found along the North American Atlantic coast, ranging from Labrador to North Carolina. Lobsters are highly sensitive to water temperature and actively regulate their location to find their preferred thermal range. This sensitivity initiates a noticeable seasonal movement each year. This change in location is a direct response to the cooling of coastal waters in late autumn and early winter, which would otherwise stress their physiological systems.
Seasonal Migration Patterns
The environmental trigger that initiates the winter migration is a distinct drop in the water temperature of their shallow, coastal summer feeding grounds. Lobsters generally prefer temperatures between 59°F and 64°F (15°C and 18°C) and begin to avoid water that drops much below 50°F (10°C). As the inshore waters cool more rapidly than the deeper ocean, the lobsters undertake a directed movement offshore toward the continental shelf edge.
This migration transitions lobsters from shallow summer residences to much deeper winter grounds. While many coastal lobsters exhibit localized movements, a significant portion of the adult population, particularly those offshore, makes extensive seasonal migrations. These movements can cover distances ranging from a few miles to over 100 miles, with some individuals traveling up to 190 miles. The general direction of travel is perpendicular to the coastline, seeking the thermal stability of the deep ocean.
Deep-Water Winter Shelter
The destination for these migratory lobsters is the deep-water winter shelter, which provides a more stable thermal environment than the turbulent shallows. Lobsters that move offshore often settle along the edge of the continental shelf or near underwater canyons. Here, they can be found at depths that often exceed 500 feet, with some individuals inhabiting waters as deep as 700 to 750 meters (over 2,400 feet).
The deep-water environment offers a thermal refuge, where the water temperature remains above the near-freezing conditions that can occur in the inshore areas. Lobsters seek out a substrate that provides ample security, often preferring muddy or silty bottoms near rock piles, ledges, or other structures. Adequate shelter is necessary to protect them from strong currents and potential predators during a period when their activity levels are significantly reduced. They may also dig or occupy burrows, which are generally defended against other lobsters.
Winter Behavior and Metabolism
Once settled in their deep-water shelters, the lobsters enter a state of reduced activity driven by the colder temperatures and lower light levels. As an ectotherm, the lobster’s physiology is directly influenced by its surrounding environment, leading to a significant metabolic slowdown. This reduced metabolic rate allows them to conserve energy during the winter months when food resources may be scarcer or less accessible.
Activity levels drop substantially, with lobsters often hunkered down in their burrows for weeks, sometimes sealing the entrance with sediment. Major biological functions, such as molting and reproduction, are halted until the water begins to warm in the spring. Feeding activity also decreases significantly, sometimes ceasing entirely, reflecting the lowered energy demand of their near-dormant state. This period of dormancy ensures their survival, positioning them to resume active foraging when the spring migration back to the coastal shallows begins.