At the Forum: Lobster Resource remains Healthy

The four larval stages of a Maine lobster. Image courtesy J Waller.

The news was heartening at the Department of Marine Resources (DMR) lobster science presentation at the Maine Fishermen’s Forum. Lobster settlement is up across the range of the American Lobster Settlement Index (ALSI) area, from Cape Cod to New Brunswick. “There’s been a slump for the past five or six years throughout the Gulf of Maine,” Rick Wahle, director of the Lobster Institute at the University of Maine and director of the ALSI, explained to the audience. “This past year there’s been a pretty significant upturn.”
The health and well-being of Homarus americanus is foremost on the minds of Mainers. Maine’s lobster harvesters landed 100,725,013 pounds in 2019, marking the ninth year in a row, and only the ninth ever, of landings that topped 100 million pounds. DMR’s senior lobster biologist, Kathleen Reardon, explained that though lobster landings were down 17% compared to the previous year, the impact was offset by a strong price. That decline was due in part to cooler waters and a later molt. “The 2019 season’s pattern was similar to 2008-2009. It was not similar to what we’ve seen during the past ten years, particularly in July,” Reardon said. DMR landings data show that in warmer years, such as 2012 and 2016, lobsters molt earlier in the season, which means by July the fishery is in full steam. In cooler years, such as 2009 and 2019, landings didn’t pick up until August. Another factor that affected the season was the availability of bait. “Total number of trips in May, June and July were 4% down from 2018 and 14% compared to 2016,” Reardon said. The lobster zone that saw the greatest change in 2019 landings was Zone C, where the total harvest dropped by 26% compared to 2018. Zones G and E showed the least change.
Lobsters themselves are also showing physiological changes, according to DMR lobster biologist, Jesica Waller. Intrigued by reports from lobstermen of finding smaller-than-usual egg-bearing females in their traps, DMR repeated a study done in 1994 on the size of female lobsters when they are capable of bearing eggs. The current study took place from 2018 to 2019. Female lobsters were collected in Boothbay and three other areas representing the western and Downeast coast (the midcoast will be sampled in 2020). Fourteen measurements were done on each female, Waller said, and three indicators of egg production identified. In statistical area 513 [western Maine] the carapace size for females was 3.5 inches in 1995. Today it is 3.3 inches. In statistical area 511 [Downeast] the size in 1995 was 3.7 inches. Today it is 3.5 inches. “Water temperature is linked to size at maturity,” Waller said. “At maturity, the female growth rate slows down. They molt on average every other year. So earlier maturity means overall smaller size.”
DMR also undertook an at-sea survey of lobster larvae along the coast last year, which will continue this year. Nets are towed through the top several feet of ocean surface to determine the abundance of lobster larvae, changes in abundance over the summer months, and size of larvae found. “The sites [of the tows] were last surveyed twenty or thirty years ago,” Waller said. “We want to do a comparison.”
Other DMR lobster surveys show results similar to past years. The department’s ventless trap survey, which gives data on sub-legal lobsters, was similarly positive to previous years to the east and west. From Friendship to Schoodic, however, the number of sub-legals was down, similar to figures prior to 2011.
DMR’s commercial sea sampling program showed that the amount of sub-legal lobsters remains higher when compared to historic levels. The number of sub-legal lobsters dropped in zone B, C and E. In other zones the numbers were up or similar to 2018.
DMR’s trawl survey, which takes place in May and October each year, provides data on all marine species found in Maine waters. In 2018 there was a decrease in the number of lobsters caught during the fall survey. However, said Reardon, the average number of lobsters caught in the deeper water, greater than 35 fathoms, during the fall survey has gone up. “The average catch fluctuates,” she added. “In Penobscot Bay, the average catch is up. In Mt. Desert area, the average catch peaked in 2015 and has been down since then. In Downeast, it peaked in 2016.”
Settlement of young lobster appears to have broadened, according to Wahle. In 2016 his project began to sample in deeper water than could be accessed by divers. The data indicate higher settlement in deep water, particularly off the Downeast coast. “Deeper water settlement mirrors the thermocline,” Wahle explained. A thermocline is a steep temperature gradient in a body of water. In Maine, this is typically a cold layer of water on bottom with a warmer layer at the surface. “There’s not much of a thermocline in Downeast water and so habitat expansion has been slight.” In the area west of Penobscot Bay, habitat expansion into deeper, formerly cooler water, has been more significant.

A very young lobster:image courtesy J. Waller
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