PORTLAND — A new scientific study says Maine fishermen who harvested millions of pounds of sea urchins for the Japanese market depleted the spiny sea creatures, turning the ecosystem upside down and creating an ideal habitat for an urchin predator that has since flourished.

With fewer urchins around to graze the seaweed following heavy fishing pressure in the 1990s, kelp beds proliferated, providing an idyllic nursery habitat for Jonah crabs. When the crabs grew to maturity, they preyed on the urchins that remained and prevented their numbers from recovering.

The University of Maine’s Bob Steneck led the research team for the study, which was published in the latest edition of the Bulletin of Marine Science. He says the urchin situation underscores the need for ecosystem fishery management.