ELLSWORTH, Maine — Green crabs, the scourge of Maine clam flats for the past several years, may have more to worry about from Mother Nature than from lobster fishermen.

According to fishery officials, the cold winter may prove to be more effective at keeping them in check than trying to get lobstermen to use them as bait.

There has been heightened interest in recent years for finding a commercial application for green crabs, an invasive species that has decimated clam flats along much of the coast. With $19.2 million in commercial landings last year, softshell clams represent the second-most valuable fishery in Maine, behind lobster.

Using the crabs as bait in the lobster fishery — which generated nearly $457 million in statewide revenue for fishermen in 2014 — has been considered as a possibility. The supply of traditional types of bait, such as herring and pogies, has been declining, and lobstermen have been looking for readily available and affordable alternatives. Some have even turned to using cowhide, which, according to people who use it, lasts longer in and out of the water than marine baits.

Baiting lobster with green crabs might not be such a good idea, however, according to a study by a pair of Canadian scientists that was presented last month at a fisheries science conference in Dartmouth, Nova Scotia.

The study indicates that a parasite called profilicollis botulus has been found in lobsters baited with green crabs, according to an article recently published by the Chronicle Herald newspaper of Halifax, Nova Scotia. The scientists did not find any trace of the parasite in lobsters trapped with other types of bait.

The parasite does not pose a threat to humans, nor does it affect the taste of lobster meat, according to the Chronicle Herald report, but it does make lobster more susceptible to predation and results in higher mortality rates among lobsters held in pounds. The record value of Maine’s lobster fishery in 2014 has been attributed in part to the relatively robust health of lobsters in the Gulf of Maine, which are shipped live to seafood markets around the world.

Bob Bayer of the Lobster Institute at University of Maine said recently that, because of the Canadian study, his organization recommends that lobstermen do not use green crabs as bait, at least until further studies can be conducted.

“These are credible people,” Bayer said of the university research scientists who conducted the study. “Don’t do it.”

Green crabs have been found in waters off New England and Atlantic Canada since the 1800s, when they hitched rides across the ocean on ships sailing from Europe.

Concern about the impact the crabs have had on this side of the Atlantic has soared in recent years as a series of mild winters have caused a population explosion along the coast. The voracious crustaceans have cleaned out clam flats and devoured eelgrass beds, leading industry and state officials to explore ways to develop markets for green crab products and to explore other ways for keeping their population in check.

According to Bayer, the cold weather this winter may do more to reduce the green crab population than anything else. Between the heavy snowfall and the unusually cold temperatures, he said, the numbers of green crabs along the coast are expected to be lower this year.

“[The winter] could kill off a lot of them,” Bayer said. “I would guess it would [cause] a big dropoff.”

Despite the concerns about green crab, the species is not on lists of types of aquatic bait that have been banned by the state for use in Maine’s lobster and crab fisheries. The Maine Department of Marine Resources has developed two lists of banned and approved aquatic species — one for saltwater and another for freshwater types of fish — that are expected to go into effect on June 1 of this year.

In an email from Jeff Nichols, spokesman for DMR, department officials indicated Thursday that the lists were developed as a “proactive” step to prevent the introduction of potentially harmful diseases or pests into the Gulf of Maine. The department studied types of bait that are being used or could be used to determine what environmental risks they might pose, they said.

“Lobster and crab fishermen have historically fished using Atlantic herring and menhaden as bait, but quotas for these species have been reduced significantly in the last decade, causing price increases and reduced availability,” the email indicated. “In response, industry sought non-historic bait sources that are less expensive and more readily available.”

The marine species list specifies that “any species that was legally caught in Maine coastal waters” is allowed be used as bait in the lobster fishery. Some types of marine species must be frozen prior to being used to bait traps in order to eliminate pathogens they might contain.

None of the species prohibited for use as lobster bait is believed to pose any concern for human consumption, according to Nichols. There is a process by which some of the prohibited baits can be conditionally approved for use if they are treated, through freezing or salting or some other method, to mitigate the risk they may pose, he added.

Industry officials outside of DMR have said the lists are not expected to cause disruption among lobstermen because the lists do not ban any bait that is in current widespread use.

Nor do they affect the use of cowhide as lobster bait, which has grown in popularity over the past couple of decades. The only type of non-aquatic bait that can be used in Maine is hairless animal hide. The use of other animal parts, or hide with hair on it, is prohibited.

About a decade ago, the state passed a law requiring all types of hide used as lobster bait be hairless after diners started finding hair deposits inside their cooked lobsters.

Bruce Worcester, a cowhide bait manufacturer based in Prospect, said Wednesday that the use of cowhide as an alternative bait has caught on in some parts of Maine but not in other areas, such as in and around Rockland. Still, he said, he sells his product on the West Coast, in Canada, and is trying to expand into the Caribbean market.

If lobstermen shun green crabs as bait because of concerns about parasites, he added, it may help increase interest in cowhide where it hasn’t caught on already.

“Parts of Maine won’t even touch it,” Worcester said. “Every area is different.”

As for whether the use of green crabs as lobster bait should be banned, Nichols said the state is keeping an eye on the issue.

“[DMR] is aware of the study… and has reached out to the author of the study to learn more,” he said. “The department will continue to monitor the use of green crab as bait and look closely at the green crab study when available.”

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Bill Trotter

A news reporter in coastal Maine for more than 20 years, Bill Trotter writes about how the Atlantic Ocean and the state's iconic coastline help to shape the lives of coastal Maine residents and visitors....