Fishing
You do not need a fishing license inside Brazos Bend State Park
Fishing from the shore or pier inside Brazos Bend State Park does not require a Texas fishing license.
Texas Parks and Wildlife exempts anglers fishing from the bank or a pier inside a state park from the standard fishing license requirement. This applies at Brazos Bend State Park's lakes, including Elm Lake and 40 Acre Lake.
The park occasionally offers ranger-led fishing programs at the park's fishing pier. Check the TPWD events calendar at tpwd.texas.gov for upcoming dates and availability.
If you fish in any waters outside the park — including the Brazos River itself — you need a valid Texas fishing license. Buy one at tpwd.texas.gov or at a local sporting goods store.
Source to confirm: TPWD – Brazos Bend State Park