A Harlem fishmonger left battered during a fatal melee over shrimp at a Manhattan fish market, said the ugly episode could have been avoided. “I saw what he was doing. He was stealing. If he wasn’t stealing, nothing would have happened,” injured worker Francisco Morales told The Post of the man accused of trying to rob the store. Morales, 38, was hurt during Tuesday’s chaos at the Fish Express Fish Mart, when Robert “Bobby” Burrell, and his brother, Malik, allegedly entered the store to steal shrimp and began assaulting him. Another worker, Junior Hernandez, intervened and ultimately stabbed the Burrell...