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Understanding the Relationship Between Lobster and Cod

Jun 10, 2010
Spring 2010
Marissa McMahan, a graduate student at the University of Maine, is working at GMRI while she completes her master’s degree in marine biology. Her interest in science began in Georgetown, Maine, where she grew up on her father’s lobster boat. She became a sternman and obtained a student lobstering license, hauling traps by hand. Now she is part of a team of five researchers who are taking a multi-disciplinary look at the interactions between herring, lobster, and groundfish, with funding from the National Science Foundation — one of the valuable outcomes of the GMRI/UMaine partnership.
When Gulf of Maine cod populations plummeted in the mid 1980s, lobster stocks took off and grew, until about five years ago when the population hit a plateau. Much work has been done to restore the cod stocks, and both lobstermen and researchers wonder, “What will happen to the lobsters?” 
Marissa has been researching lobster behavior in the presence of predators, along with GMRI Scientists Graham Sherwood and Jon Grabowski. They observed the movements of five lobsters in a pound at The Lobster Conservancy in Friendship, Maine, using state-of-the-art acoustic receivers. Without predators present, the lobsters explored the perimeter, moved around frequently, set up territories, and tended to stay in the deepest and coldest parts of the pound. When three cod were released into the pound, the lobsters moved around significantly less. The team is conducting a second phase of this experiment this summer. They hope to gain important insights about the relationship between lobsters and cod.