The fish you are referring to is likely the “smoked whitefish.” This is a type of freshwater fish, often with a small mouth, that has a fat or oily flesh. It is commonly found in the Midwest and along the East coast of the United States. Smoked whitefish is a popular regional delicacy and is often sold as a smoked fish product. It can also be purchased fresh, either whole or in fillets, typically from specimens weighing two to six pounds.