We play at fishing on the Frio but I know for a fact there there can be big fish on the Frio. When the Utopia Road bridge was about two years old we were under the bridge talking to some people and a young teeneaged boy came up, so proud, he had just caught a huge catfish. It was still moving when we saw it. My husband and another man judged it to be between 20 to 25 pounds. Big, no doubt, for that water. Since then, we stay at a place just on the other side of Leakey, near the airport where the Frio and the Dry Frio merge and the owners were showing us a big catfish that hung out for at least two years. We have not seen it in the last two years but it has to go somewhere. This is not to get your hopes up but there is fish bigger than your hand in that river. Also check out the Sabinal and Nueces Rivers, there has been some interesting articles in the Houston Post about fishing the three rivers. Good luck and I am taking my fishing tackle when we are there in late May, you never know.
Sandy