A gauge for measuring the size of a clam includes a C-shaped body that has a base that extends from a first axial end to a second axial end, a first leg extending from the base proximate the first end and a second leg extending from the base proximate the second end. A gap extends between the first leg and the second leg. The gap having a predetermined magnitude selected to match minimum size limitations for keeping a clam. The gauge being removably securable to a shaft of a clam rake.