R-08-04 Modeling ecosystem dynamics for American lobster (Homarus americanus) in the Gulf of Maine

Yong Chen
218 Libby Hall
School of Marine Sciences
University of Maine
Orono , ME 04469
Email Yong Chen

In the U.S., most fisheries are managed on a species-by-species basis. Scientists and fishermen recognize that this conventional approach is often unsuccessful, because it does not account for the complexity of ecosystems, including interactions among and between different species.

The American lobster is an example of a fishery that is managed as a single species yet is one that could have ecosystem-wide influence. Lobster is one of the most valuable commercial fisheries in the northeastern U.S., with most of the catch landed in Maine. Maine’s coastal communities depend heavily on the lobster fishery, and the recent increase in the Gulf of Maine lobster population and production, and decrease in many other species such as groundfish, raises some questions that Chen’s research is attempting to answer. For example, are the changes in the various fisheries related to warming ocean temperatures? A decline in lobster predators? An excess of discarded lobster bait (herring)? If groundfish recover, will lobster production be affected? Etc.

Chen’s recent research (funded by Sea Grant, R-06-04) improved the stock assessment model for the lobster fishery (and has been adopted by the Atlantic States Marine Fisheries Commission). The new approach is still a single-species model, however, and is not suitable for answering the above questions.

Now, Chen and his research team have compiled historical information and analyzed data collected in the state’s in-shore trawl fishery, and developed a preliminary dynamic ecosystem model for the lobster fishery. At the same time, they are developing alternative management strategies, which will be evaluated for their possible ecosystem and population level consequences. The model database includes most species that can potentially influence the population dynamics of American lobster in the Gulf of Maine. Results from this modeling effort suggest that heavy fishing pressure on cod in the 1980s might have contributed to the high lobster stock biomass in recent years, and such interactions should be considered in future fishery management efforts.

2-year project, 2008-2010
Total Sea Grant funds: $135,380

Associated publications
Taking Stock, UMaine Today magazine, November/December 2008.