A pilot program to collect used oyster and clam shells from Atlantic City casinos and restaurants and use them to create oyster colonies in the Mullica River has been so successful that it is being expanded to other parts of the state, officials said Monday.The state Department of Environmental Protection started a program in 2019 to collect shells from diners’ plates at Hard Rock Hotel & Casino Atlantic City and the Knife & Fork restaurant and Dock’s Oyster House in the resort.Those shells were cleaned, dried and dumped into the riverbed, where baby oysters, called “spat,” settled upon them to grow new oyster colonies.On Monday, the state enlisted the aid of the world’s largest food distribution company, Sysco, which services 800 restaurants between the Connecticut coast and Cape May.