The state Division of Marine Fisheries yesterday expanded closed shellfish areas to include the eastern side of Nantucket Sound due to red tide. The closure does not affect fish or shellfish harvested and landed in Vineyard waters.

The agency sent out the notification for the benefit of shellfishermen and fish markets that sell shellfish wholesale and retail. Affected shellfish include surf clams, ocean quahaugs, mussels, carnivorous snails and whole sea scallops. Those scallops are exempt if only the adductor muscle is landed.

Though the closed area is expanding and includes parts of Cape Cod Bay, as well as waters east of Cape Cod and Nantucket, the situation is improving.

J. Michael Hickey, chief shellfish biologist for the state, said bloom has run its normal course: “It appears to be dissipating,” Mr. Hickey said.

Earlier this week, the state closed shellfishing in federal waters outside the state’s waters. Federal waters begin at about three miles offshore, depending on the area.

Red tide is a toxic marine algae that when ingested by shellfish can make them harmful for human consumption. The bloom began in the Gulf of Maine and it has been expanding into the waters of Cape Cod Bay, around Cape Cod and out to Georges Bank.

More details about the closure are available at the division Web site.