The American Lobster in a Changing Ecosystem

by Catherine Schmitt

Today was the first full day of the American Lobster in a Changing Ecosystem: A US-Canada Science Symposium. More than 100 of the region’s top lobster scientists have gathered in Portland, Maine, to share their research.

Maine Department of Marine Resources Commissioner Patrick Keliher in his welcome remarks reminded the scientists that they also are here to help managers and fishermen to define “the new normal.”

The new normal = lots of lobsters.

UMaine’s Dr. Robert Steneck explained, “This is the only fishery that’s been targeted for 150 years and is doing better today than ever before.” Instead of being surprised at abundance, Steneck promotes a long-term perspective. While at one time the Gulf of Maine was dominated by cod, today the big fish are “ecologically extinct,” leaving lobsters to rule the sea floor, a kind of herd in what has become a “domesticated ecosystem.”

In some places, such as mid-coastal Maine, two lobsters can be found every square meter, the highest density on the planet. Scientists get concerned about high density and low diversity, because crowded animals are vulnerable. In southern New England and Long Island Sound, a combination of low oxygen, warm water temperatures, and potentially exposure to pesticides/spilled oil, and/or other pollutants stressed lobsters to the point where they were susceptible to disease, according to Dr. Jeffrey Shields of the Virginia Institute of Marine Science.

What is this cod and lobster dance? Marissa McMahan of Northeastern and UMaine discussed how the mere presence of a predator can influence the behavior of prey. Lobsters can smell cod, and in McMahan’s experiment the presence of cod in a closed embayment restricted the movement of lobsters. The cod, however, are visual predators, and so they eat lobsters during the day. At night, bigger lobsters eat smaller lobsters in what graduate student Noah Oppenheim called “rampant infanticide.” The food web has changed that much.

Shell disease, cannibalism, unpredictable behavior like this years famous early shed—hard to say yet if this is the new normal. There’s still two more days of lobster science.