Getting too close to a family of 15 bottlenose dolphins that has taken up residence in a river near the Jersey Shore could prove costly.

Authorities have stepped up enforcement of a 50-yard exclusion zone around the mammals to help protect them, and violators could be fined as much as $10,000.

One reason for the crackdown was a massive fireworks display held Thursday night in nearby Red Bank. It attracted tens of thousands of spectators on land and hundreds more in boats in the Shrewsbury River, where the dolphins have been cavorting since mid-June.

State police and federal officials monitoring the dolphins say there were no immediate reports of any incidents with boaters during Thursday's festivities.

Authorities recently scrapped plans to try to coax the dolphins back out to sea, deciding instead to keep people away from them.

Fourthof July fears mount for wayward dolphins