The discovery of baby lobsters in the deep waters off eastern Maine could be good news for the future of the U.S.’s most valuable fishery.

Since 1989, scientists led by University of Maine professor Richard Wahle have looked for baby lobsters at 100 shallow-water test sites from Rhode Island to New Brunswick to monitor the health of this fishery. The number of babies found in the samples started to decline about a decade ago, leading scientists to worry that a population bust may be looming.

“We couldn’t find the settlers,” Wahle said Monday. “Increasingly, we found they weren’t showing up where we had always found them.”

When the unusually small number of baby lobsters did not lead to a smaller catch seven years later – that’s how long it takes a lobster to grow big enough to harvest, and most of Maine’s annual haul is lobsters just large enough to legally catch – Wahle began to look for another answer, and he thinks he may have found it lurking in the deep, not-as-cold-as-you-think waters off Cutler.

Wahle wondered if the small lobsters ending their four-week float through the open sea were literally settling down in places where researchers weren’t looking for them. The American Lobster Settlement Index looks for settlers at test sites that are about 32 feet deep, Wahle said. Perhaps, as the Gulf of Maine has grown warmer, the babies were finding suitable habitat in deeper waters.

With funding support from Maine Sea Grant, and later Ready Seafood Co., Wahle has looked for baby lobsters off shore and has found them hunkered down in the cobble more than 250 feet below the water’s surface. He has found them in the deep waters off both Casco Bay and Cutler, but the number of deep-water babies in the east far outnumbers those found off the southern coast.

“Eastern Maine used to be a settlement desert,” Wahle said. “Not anymore.”

That is because the deep waters off downeast Maine are actually warmer than the deep waters off southern Maine. While that may sound wrong to anybody who has gone swimming in both Eastport and Portland, the strong tidal currents of the Bay of Fundy keep the waters of eastern Maine thoroughly mixed, so water temperature there is about the same from top to bottom.

The tides are weaker in southern Maine, so the water column stratifies, with warmer waters on top and colder waters on bottom, he said.

That means the tide-churned deep waters off eastern Maine are actually warmer than waters of the same depths found off the southern coast, giving baby lobsters there a much larger ideally suited nursery habitat.

In the summer, when fourth-stage larvae are beginning to dive down to the ocean bottom to look for a suitable place to settle, scientists have found that lobsters will actually turn around and return to the surface if the water temperature dips below 53 degrees. But with the Bay of Fundy currents in place off eastern Maine, baby lobsters can be found as far as several miles offshore.

Wahle is heartened by these preliminary findings, but says he will need to collect more data in the coming years to see if this theory of baby lobster settlement holds up over time. But an expanded nursery habitat driven by rising ocean temperatures would help explain the explosive growth of lobster landings in eastern Maine ports, Wahle said.

It would also be good news for the longterm future of Maine’s $1.4 billion lobster industry. Several computer models that address rising ocean temperatures have predicted a 40 to 62 percent decline in Gulf of Maine lobster populations over the next 30 years, but Wahle’s deepwater settlement findings suggest the Bay of Fundy effect may insulate eastern Maine from these predicted declines.

Other researchers, including Wahle himself, are studying other factors that may be contributing to the decline in baby lobsters found at the American Lobster Settlement Index sites, including a decline in the copepods that these settlers like to eat and an increase in the predators who like to eat the settlers.

With continued support from Ready Seafood and University of Maine, Wahle plans to continue his deepwater settlement research. The professor would like to expand the number of collection sites to different areas of the Maine coast, and to test in even deeper waters in eastern Maine, but funding restraints will limit him to the Casco Bay and Cutler sites, at least for now.

“We are excited to be a part of a research project that is improving our understanding of Maine’s lobster resource,” said Curt Brown, a Cape Elizabeth lobster biologist and fisherman employed by Ready Seafood. “Lobster is the lifeblood of Maine’s marine economy and we see this project as an investment in not only the future of our company, but the future of our industry.”

Penelope Overton can be contacted at 791-6463 or at:

poverton@pressherald.com

Twitter: PLOvertonPPH