True sardines are young pilchards, a type of herring. They were first caught in abundance off the coast of Sardinia in the Mediterranean Sea, and are considered the first fish to be packed in oil. In the United States, a species closely related to the original Sardinia pilchardus is fished off the California coast. “Sardines” caught off the shores of Maine are actually the young of a different type of herring. Sardine oil is more costly than the fish, so canners attempt to package as many sardines in each can as possible.