What Texas laws protect fishing lines from poachers running our lines and taking fish?

None really. You would have to report to a game warden, and then he would have to catch them in the act of running lines with someone else's gear tag on them.

Lead poisoning usually stops it.

With a hole in the boat it's hard to dip water and run lines

If your using throw lines, try white line and tie them in the trees(you want them to see them). Make sure they have to get the boat up under the trees. Have a few rubber snakes in the trees ready to fall when they pull the lines. Stopped our poacher problems. Especially when they shot three holes in their own boat.

Sounds like you were the man with the plan. I'm wondering what kind of response a fake human head would bring on the end of a jug line?

As to this problem & remedies ... Sad to say, they are those who wish to take the easy way out. There used to be a law that it was illegal to steal edible meat. I was told this in the 70s or 80s. I recall one game warden back on my days in the 80s on the Trinity River (a few miles below TX 21 bridge). Very friendly one who was a champion of all legal fishermen. It had just been made a law as to tagging one side of your trotline. He explained why it was best to tag both sides & gave an example of one he was checking (for legality). It was hung & he could not get the other side. The side he was on, did not have the tag. He could not get the other side to look. So by law, he was required to pull it, as no tag, it was not legal. But as he was retrieving it, it came loose & then he could retrieve the rest that he could not find or get to. Sure enough, it had the legal tag. So he neatly piled it on the bank on that side for the fisherman to hopefully find. He explained that he would not have pulled it, had a tag been on both sides.

He also said it was not required to tag throwlines. But he explained that if it was tagged & he came upon someone running it, that did not match the tage, he would either ticket them, or possibly more. But he would make sure they were deterred from ever doing it again. He caught some guys who were using someone else's boat (he knew the rightful owner). He took care of that problem. I doubt if they will ever use someone else's boat again, without permission.

You can tie them underwater (out of sight). That helps.

Sounds like the only sure fire way is to stay with your lines until you are done fishing and then take them up. That's what I do with my noodle jugs when I fish with them. There are people out there that will steal nickles off a dead man's eyes. I hate a thief bout as much as a rattlesnake and I kill all rattlebugs.

Trespass laws generally. Taking fish off someone else's trotline is theft. It might be something covered under this statute:

Vernon's Texas Statutes and Codes Annotated. Parks and Wildlife Code. Title 5. Wildlife and Plant Conservation. Subtitle B. Hunting and Fishing. Chapter 62. Provisions Generally Applicable to Hunting. Subchapter A. General Provisions. � 62.0125. Harassment of Hunters, Trappers, and Fishermen

But, you have to be able to prove the person did it. As mentioned above, the GW has to see it happening. Or, you could get video of the poachers stealing from your line.

I have had only one person we caught in many years...still wrong as many more did take fish off that I didn't see. There is little help for the legal fisherman ...I suppose. I do wish I could just put holes in their boat...but, now days they might also be prepared and also put some holes in my boat. So...just something we have to put up with.
I will take down their boat number and turn it into the game warden even if it doesn't help. Rest assured I will let them know that they are running my lines.

thanks for your input

There are a few people who run other people's lines and that is bad . But so is the huge number of people who leave jugs and trot lines in the lake for ever. I would like to see them file charges against these people and they are a lot of them.
Johnny