SAINT JOHN, New Brunswick – They look as appetizing as a cactus and taste like low tide, but not even that has been enough to keep New Brunswick’s green sea urchins out of a prickly predicament.

Dredged up from the bottom of the Bay of Fundy and shipped off to sushi bars in Japan, the urchins command such high prices that their population may be slipping.

Just weeks away from the start of the annual season, there is debate between New Brunswick fishermen and scientists over the risk posed by catching too many of the invertebrates, once considered a nuisance by some of the same fishermen who now pursue them.

Ten years ago, New Brunswickers hauled in about 4.2 million pounds of sea urchins with a market value of a little more than $4 million. In 2006, those figures fell to 2 million pounds and $1.8 million.

The story is similar to what happened in Maine, where the harvest rose rapidly in the early 1990s before peaking at more than 41 million pounds in 1993. By last year, landings had fallen to less than 3.4 million pounds, the smallest harvest in 20 years.

Only 32 fishermen have licenses to catch sea urchins in New Brunswick’s two commercial zones – off Grand Manan and between Deer Island and Maces Bay.

The urchins have been in such short supply that Grand Manan’s commercial fleet decided not to fish for them in 2005-06. Last year the fishermen agreed to reduce their self-imposed catch limit by two-thirds – to 387,000 pounds from 1.2 million pounds.

“We are hoping to maintain the same quota this year as last,” Harold Cossaboom, a lobsterman from Grand Manan, said Tuesday as he was dropping his traps for the season, which opens Dec. 10. “Scientists want a reduction in the quota, but we don’t support that. We unanimously figure we have taken enough measures, and in our opinion, the fishery is coming back, or at least stabilizing.

“But we all have agreed to closely monitor our catch rates, and if it looks like the population is in trouble, we’ll say, ‘We have a problem here’ and shut it right down.”

Green sea urchins are prized in Japan, where discriminating diners consider the roe to be a delicacy.

David Robichaud, a scientist in St. Andrews, New Brunswick, with Fisheries and Oceans Canada, said information on sea urchins is lacking, but it appears that certain populations are in trouble.

An East Coast fishery for them developed only in the last few decades, after the slow-growing invertebrates were nearly wiped out off Japan and the Pacific coast of North America. It takes sea urchins nearly 12 to 15 years to grow to 2 inches, which is the legal minimum size.

“It appears the population is down drastically worldwide compared to what it once was,” said Robichaud. “There has been a gold-rush approach around the world.”

Fikret Berkes, a marine scientist and Canada Research chairman based at the University of Manitoba, recently cited the sea urchin population in the Gulf of Maine as one that was exploited to satisfy the sushi market before resource managers had an opportunity to step in.

The catch in New Brunswick has to be carefully monitored so as not to upset the ecological balance, Berkes said, saying that cod and haddock feed on the sea urchins, and sea urchins feed on kelp. Without a healthy population of cod, the sea urchins run amok. And without them, kelp beds grow wild.