The fibreglass fishing rod held by the statue in the rowing boat was snapped by someone between 5pm on Friday, February 11 and 10am on Sunday, February 13.
The museum’s chairman Bill Quarry said: “This is about the fourth time the rod has been broken, but the police caught one of them and he was fined £600.”
“It’s so very disappointing, every Saturday night there’s trouble round there.”
Police are appealing for witnesses or anyone with information to call 101 quoting incident 1598 of February 14, or call the independent charity Crimestoppers completely anonymously on 0800 555 111 or at http://ow.ly/urQm50HVe4