Commercial Fisheries News - July 2000

Migration: What we know

Spiny lobsters undergo the most familiar and famous lobster migrations in the sea. These claw-less relatives of the American lobster line up single file to march offshore into deeper water across the ocean floor in long queues or lines, apparently in response to the onset of summer and fall storms.

Although similar aggregated, synchronized movements have not been reported for clawed lobsters, there is ample evidence that they, too, make impressive movements.

One key factor contributing to our knowledge of spiny vs. clawed lobster migrations is the manner in which they have been observed. Spiny lobster migrations have been watched and filmed underwater, while clawed lobster migrations are deduced from tag and recapture studies.

Over the past several decades, various researchers have marked adult and adolescent lobsters with individually coded visible tags, which are then picked up by fishermen. Scientists use the tag information to compare the sites of release to the subsequent capture site and estimate straight-line distance traveled.

Most lobsters have been caught relatively close to the site of release. Others have roamed from as far as the mouth of the Bay of Fundy to southern Maine — greater than 300 kilometers (km) or 180 miles — and from Long Island Sound, NY offshore to Veatch Canyon, greater than 200 km (120 miles).

Multiple recaptures of egg-bearing female lobsters reveal a pattern of movement from shallow warm waters during the hatching, molting, and breeding season, then to deep water for the winter.

Deep waters are warmer than shoal waters in winter. By moving into deep water, egg-bearing female lobsters are promoting the development of their eggs because maturation occurs faster in warmer water. They then move back into shoal water where eggs hatch and are released over the course of several days or weeks. Hatching occurs primarily in the springtime and early summer in shallow coastal waters and in the shoal waters of the banks.

Recent tagging of Year 1-Year 4 juveniles reveals that young lobsters also undertake seasonal migrations from shallow to deeper waters. Spending their summers near shore may result in faster growth rates. Walking to deep waters may allow them to remain active in winter. Although short travel distances — less than 5 km — have been recorded during the summer months, long-range distances traveled and location of winter grounds are unknown.

In general, the young return to their nursery grounds in May and depart in November. The arrivals and departures are abrupt. Perhaps they travel together under cover of night. One November, I witnessed their date of departure. It came with the first snowfall of the year. One day, the young juveniles were present in the shallow cove in great numbers. The next day, we had our first snowstorm, and the day after there was hardly a lobster to be found. I wonder how and where they went.

Ask the Lobster Doc