Tex. Parks & Wild. Code § 78.005

A person who possesses a valid fishing license or who is a resident and is exempt from licensing requirements under Section 46.002 of this code may take or harvest from the public water of the state, for personal use and consumption only, not more than 25 pounds a day of whole mussels and clams, including shell and soft tissue, or 12 pounds a day of mussel and clam shells.