The record breaking hauls of the lobster industry -- along with the booming green crab population -- are expected to continue over the next few decades. The future of the lobster fishery and the invasive green crabs were among the topics covered at a talk held by the Sunrise Senior College on February 9 featuring Dr. Brian Beal of Down East Institute (DEI).
      Beal began the talk with some historical perspective, including describing the work of DEI. Founded in the mid 1980s with the intention of building viable shellfish hatcheries, providing community education and serving as an aquaculture training facility, DEI has been actively involved in monitoring and contributing to the shellfish population. On June 6, 1987, the facility saw its first successful clam spawning; since then, it has provided hundreds of millions of seed clams for area tidal flats.
      While seeding the flats has boosted the clam population, it has been more difficult to tell if DEI's efforts to increase the lobster population have been effective, Beal said. This is due to the numerous contributing drivers affecting the population and the complex relationship between species.
      The lobster population in the Gulf of Maine has significantly increased, Beal said, which is indicated in part by the size of the lobster catch. Between 1930 and 1989, the average annual catch was around 17.7 million pounds. In 1990 it skyrocketed to more than 28 million pounds, rising to 53.5 million by 1999. The year 2011 was the first year the Maine lobster catch was more than 100 million pounds. Since then, 2016 saw the highest catch at 132.6 million pounds.
      Rather than being attributable to significantly more traps in the water or a lack of management measures in place -- neither of which is the case, Beal explained -- the single biggest driver is temperature. According to Beal, the Gulf of Maine is warming faster than 99% of the world's ocean. "That's been happening for quite a while," he shared, adding that it's been happening since the 1980s. With a recent reading of 420, Beal said it was "the highest it's been in the Gulf of Maine in February in a long time."
      The warmer temperatures prompt lobsters to reproduce sooner. In the past, eggs weren't visible on lobsters that were less than two pounds. The warming temperatures have been shifting that lower and lower. "Now, animals that aren't even one pound are reproducing," Beal said.
      "What we don't know is what will happen in the future as we continue this trend," Beal said, noting that there are multiple inter species relationships at play.
      To illustrate his point, Beal described the sea urchin fishery. Prior to 1985, there was essentially no sea urchin fishery in Maine. When demand arose in Asian markets for roe, the gonads of male and female urchins, the Maine fishery quickly took root. Sea urchin landings peaked at just under 45 million pounds in 1995 and then swiftly fell. The fishery hasn't rebounded from its peak; in 2020, it totaled just over 1.2 million pounds.
      The crash of the sea urchin population contributed to a boom in the lobster population, however. As herbivores, sea urchins eat kelp, and kelp is a prime habitat for lobsters to use as nurseries. With fewer urchins around, lobsters had more opportunity to flourish.
      Similarly, the lobster population increased due to the cod fishery decreasing, Beal said. Cod are predatory and eat young lobsters, which had the effect of keeping the population lower. The cod industry peaked in 1991 at 21.2 million pounds; by 1999, it was down to 1.5 million pounds. Today it is virtually nonexistent as a fishery with fewer than 60,000 pounds registered in 2020.
      In the case of sea urchins, their sudden population crash had another influencing factor beyond the fishery itself: green crabs.

Green crabs play major role in other populations
      A highly invasive species, European green crabs first arrived in North America in 1817, Beal said. The crabs were carried in the hulls of ships that had rockweed in their ballast. In 1951 they were discovered in Washington County, and they have been rapidly proliferating ever since.
      Green crabs are in the top 10 of Maine's invasive species list due to their fecundity, or rate of reproduction, Beal explained. A 2" crab can host 185,000 eggs. With the temperatures in the Gulf of Maine warming, the number of green crabs has dramatically increased.
      Some species have seemingly vanished as a result. Asked where the mussels are, Beal said, "They aren't going extinct. They are going extinct in the intertidal zone due to green crabs."
      If young mussels land anywhere in the intertidal zone, they are very likely to be eaten quickly by green crabs, Beal said. At the size they settle at, mussels are 1/5 of a millimeter, while young green crabs are 1 millimeter. Mussels that settle on ropes or under boats are more fortunate, as green crabs can't swim.
      As "voracious predators," green crabs make short work of whole spawning cycles for numerous species, including softshell clams and urchins. Fortunately for some species, "everything eats green crabs, including green crabs," Beal said.
      Asked if green crabs could be a viable fishery, Beal said that green crabs "taste great," adding, "I can't tell the difference between rock and green crab in taste and texture." To make a sizable dent in the green crab population would require a fishery larger than today's lobster fishery, Beal said.
      Provided water temperatures continue to rise as they have, Beal anticipates both the lobster and green crab populations will continue to boom over the next 20 years. "I think we are going to have a strong lobster fishery for a long time to come," Beal said, adding that eastern Maine in particular is favorably positioned.