There are no regulations regarding PRIVATELY OWNED ponds. I have several and manage several more for others. Selective catch and release is a management tool that must be used to keep a pond from getting "bass heavy". Every year, I toss or recommend tossing every bass under 10 inches on the bank. This starts the second year after initial predator stocking. I fillet the ones that are 12 to 13 inches. OK, if a bass is really healthy, I may release it. I never keep a large bluegill because they are my brood stock that generates the forage base for predators. If a body of water is under 20 acres, never return a crappie to the water. Channel cats are mostly stock and eat fish. They seldom accomplish a successful spawn in a small body of water. And, they are cheap to restock. Now, all of this said, the Landowner is the final and only law on managing his ponds and the culling. If he follows the catch and release mantra used on public water, it's his business and nobody elses.
If you are fishing City or County owned property, they are considered public waters and TPWD regs generally apply. Check with the Parks Department and the Game Warden on this. These regs can vary.