Walk or kayak along the Maine coast, and seaweed seems to be in endless supply. Those who gather the thick, leafy plants for a living, however, worry that someday their waterborne crop could be gone forever if sustainable harvesting guidelines are not put into place.

Although the seaweed supply in Maine shows no imminent signs of dwindling, a look to the north says prudence is warranted. By 1986, so much seaweed was harvested in the Annapolis Basin on the Nova Scotia coast that the area had to be closed to harvesting to allow the plants to recover.

“Mainers saw what happened and they didn’t want to repeat it here,” said Jill Fegley, a graduate student at the University of Maine, who has studied seaweed regeneration and has advised the Maine Seaweed Council and the Department of Marine Resources on what should be included in regulations governing how the plants are harvested.

There are now no regulations on the seaweed industry other than a requirement that harvesters obtain a permit for $10. The permits do not stipulate how much or where harvesting can be done. So, the council and DMR are putting together a set of rules that will include cutting and reporting guidelines, among other things.

The reporting will come in handy, said Pete Thayer of the DMR, because now no one knows how much seaweed is actually harvested along the Maine coast. The major harvesting areas are north of Portland and range from Boothbay to Cobscook Bay. Several species are harvested, but the lion’s share of seaweed gathered is rockweed. The leafy, brown seaweed is used to pack lobster for shipment as well as for fertilizer, food additive and animal feed supplement.

Irish moss and dulce are sold to the health food market, kelp is used in food and hygiene products, and sea lettuce and nori are eaten in salads and sushi.

Thayer said he hoped to have records of the amount of seaweed harvested by species, weight and location by next year.

Bob Morse, president of the Maine Seaweed Council, said the group’s sole mission is to ensure that seaweed is harvested sustainably.

“There’s not a shortage of seaweed where we harvest,” said Morse, who runs Atlantic Laboratories Inc. in Waldoboro and has been involved in the business for 28 years.

Atlantic labs is one of three large companies that buy rockweed from Maine harvesters. The others are Source Incorporation in Brunswick and Acadian Sea Plants, a Canadian company that works in Cobscook Bay.

The companies buy seaweed from the more than 220 licensed harvesters in the state. Several hundred people are employed by the companies to process and ship the seaweed.

Morse said seaweed processing is a multimillion-dollar industry in Maine, although he said he didn’t have hard numbers. A survey on how much money the industry generates is being done, he said.

The seaweed business is growing — albeit slowly, Morse said. “It’s not gold-mine growth like urchins have,” he said. But, he predicted, seaweed harvesting will be around for a long time in Maine.

The key to ensuring that is the case, Morse and others say, is to formulate regulations that require responsible harvesting.

“As long as seaweed is harvested responsibly, the ecosystem is resilient and it will rebound from a harvest,” Fegley said.

Fegley’s own studies along the central Maine coast bear this out. She made different types of cuts on several rockweed beds and observed the growth rate for two years. When the seaweed was cut leaving only about 7 1/2 inches of plant behind (less than Canadian regulations require), 65 percent of the plant’s original mass had grown back in two years. When cuts were made leaving at least 15 inches behind, 88 percent of the mass was regenerated.

In addition to cutting heights, Fegley said the council is discussing rules regarding cutting techniques. Most harvesters cut by hand, which ususally does not harm the plant. But if the cutting implements are not sharp enough, they sometimes rip up the entire plant, including the “holdfast,” the stemlike portion that holds it to the rocks. If this happens, the plant cannot grow back.

In Canada, cutting heights are set by the federal government, but provincial governments can set even more stringent rules, which New Brunswick has done.

Many harvesters were concerned that Acadian Sea Plants, the Canadian company that recently began operating in Cobscook Bay, would take advantage of Maine’s lack of regulations and take as much seaweed as possible. This has not happened and, in fact, the company instructed its harvesters in Maine to adhere to the Canadian rules, Fegley said.

The Canadian government also surveys the amount of seaweed that is growing each year and then sets limits on how much can be cut in given areas. The Maine Seaweed Council is contemplating this approach.

Another touchy topic the council is discussing is whether to lease harvesting areas. Many countries have adopted this approach to control how much is cut in a given area and by whom.

A draft of a seaweed management plan is expected to be released later this month. It will then be the subject of public hearings before being adopted.