Comal WORD has specific river laws pertaining to the Guadalupe River inside Comal County. These include:
GRTU encourages all anglers on the river to practice catch and release, using single hooks (no treble hooks) that are barbless to best protect the fish in the river. All GRTU Lease Access Members (LAP), as part of their inclusion in the program, agree to practice catch and release on all trout caught on the Guadalupe River downstream of Canyon Dam
If you are not a LAP member and do want to keep a fish, there are various regulations mandated by Texas Parks and Wildlife Department (TPWD) regarding keeping trout on the Guadalupe River below Canyon Dam.
See the TPWD website for regulations on all fish species on the Guadalupe River