BAR HARBOR — For the local lobster fishery, there is now and there is the future.
The “now” looks solid for local commercial lobster fishery, based on findings reported in the 2020 Atlantic States Marine Fisheries Commission Lobster Benchmark Stock Assessment, which reported the stock at “record high abundance levels.” The good news continued: “Stock projections conducted as part of the assessment suggested a low probability of abundance declining below the abundance target over the next 10 years.” The Gulf of Maine lobster fishery now accounts for 90 percent of U.S. lobster landings, and, overall, landings have increased fivefold in Maine from 1982 to when it peaked in 2016.
The outlook for southern New England remained poor, with a depleted fishery and no signs of resurgence. The research was conducted by several organizations, including the Department of Marine Resources, Gulf of Maine Research Institute and the University of Maine’s Sea Grant program and Lobster Institute. The assessment, released in October, was based on surveys conducted from 2016 through 2018.
However, once the research turns to lobster settlements the future does not look as bright.
“There’s this really puzzling disconnect between the surging numbers of lobsters we’ve been seeing over the past decade and the decline in larval settlement that we’ve seen,” said Richard Wahle, director of The Lobster Institute at the University of Maine.
Wahle explained that an abundance of lobsters means more lobster egg production, so the fact that the fishery is experiencing a period of very low larval settlement is a concern for the fishery’s future.
“That’s sort of the $64,000 question here,” Wahle said.
Different factors come into play with larval settlements. Water temperature, food sources and mortality rates all play a role. But Wahle zeroed in on stage 4 of larval development, the post-larval phase and the time when young lobsters start to settle on the seabed.
“The first stage correlates very well with the brood stock abundance, which is what you’d expect,” Wahle said. “The more egg production there is, the more larvae is in the water. There’s something happening in the intervening stages. Something’s happening between stage one [larvae] and the post-larval [stage 4] phase.”
Wahle said researchers focused on this issue found the prime suspect to be copepods, tiny crustaceans that are a key food source for the stage four, post-larval lobsters. This is where the warming Gulf of Maine waters comes into play as copepods move north toward the St. Lawrence River.
“So, are [the stage 4s] moving to where the food is?” he asked. “The one thing that stood out was the correlation between stage 4 abundance and this copepod.”
While scientists well know that correlation is not necessarily causation, Wahle said that “it becomes more and more compelling that maybe these post–larval [lobsters] are starved when these little copepods aren’t present.”
So where have the copepods gone? Are the stage 4 lobsters following them? Is larval survival limited by the supply of copepod?
“The jury’s still out,” Wahle said. “We’re still testing this question. It might not be surprising if we find copepods are a survival driver. It’s a key food for everything from herring to right whales. It’s such a key piece of the food web.”
The Lobster Institute is now studying the depth range of settlements using methods that bring a range of data beyond what divers can obtain, from lobstermen and other industry stakeholders, to help draw a clearer picture, Wahle said.
The lead lobster scientist at the DMR, Kathleen Reardon, shies from over-simplifying the connection between a warming Gulf and lower landings in the future. Referencing the 2016 lobster landing peak, she noted that stock in all Maine lobster fishing areas increased.
“While eastern Maine (generally east of Penobscot Bay) drove the huge increases in landings, it is important to note that western Maine did not decrease over that same time period, it just did not increase at a similar rate,” Reardon said. “With that evidence, I am uncomfortable with the statement that the population has migrated north — it is more that the productivity of the lobster population has increased in areas where environmental conditions have become more favorable or optimal, likely due to warming waters and changing dynamics.”
The ASMFC assessment also indicates that conservation and sustainability methods employed by the Maine fishery over the years have worked.
“I think the industry can take heart in the fact that they’ve managed this fishery admirably and more than sustainably,” Wahle said. “That was one of the takeaways.”