BOSTON -- Crews are searching the waters off Massachusetts on Friday after a fisherman reported possibly seeing a shark.

The fisherman told state police said he was fishing when something large, possibly a shark, took his bait.

The incident happened near the mouth of the Merrimack River in Salisbury on Friday, according to the Coast Guard. The state police were using a helicopter to search the waters.

Wendy Fox from the Department of Conservation and Recreation said nothing "dangerous" was sighted off Salisbury, and officials believe the creature was most likely a basking shark.

Friday's report is the latest in a busy shark season in Massachusetts. Last week, a shark was spotted off Chatham; and a few days before that, a great white was spotted by a whale-watching boat off Gloucester.

The Coast Guard issued a warning to boaters about predatory sharks in early July, which seem to be attracted to the Massachusetts coast by large schools of blue fin tuna and seals.

In June, the fishing boat Sweet Dream III was tuna fishing on Stellwagen Bank when the crew spotted one of the predators. After a one-hour fight, the crew caught the 7-foot shark, tagged it and released it.