I've got a backyard pond. Lots of bass. My son was practicing fly casting and 2 out of the fist 4 bass he caught went into some sort of seizure as soon as they were landed where their mouth was frozen wide open and the body curved rock hard. I wish I had taken a picture, but didn't. I couldn't even force their mouth closed or unbend them. I've never seen this before. They died when I returned them to the water since they were still in this frozen type seizure and turned upside down. Has anyone ever seen this? I've reached out to the fish farm where I get my replacements and they've never seen it either. I can't find anything like it on google. Any ideas?

Shock? All I can think of

That seems really odd. Are you sure your son didn't drop them or anything? All I can think of would be if they got popped on the head really hard or something.

It doesn't make sense that they would go from active and feeding to seized up and dead immediately. I would be really curious to hear if you find a cause on this.

Do you need some new genetics?

Super weird. I've just absolutely DRILLED small bass in heavy timber in Lake Fork with a stiff rod, 20# test and a 3/0 hook and have never had any act like that. I set the hook on some so hard that 1-1 1/2 pound bass came completely out of the water (It's Fork, you never knew if it was a little dude or a 12#er you needed to get out of the timber fast).

You don't need to rip the lip off the fish to land it
http://www.bassfan.com/news_article/7410/be-mindful-of-your-hook-setting-mechanics#.WUBqYoFOmEc

This isn't a hook set problem. These fish are being caught on a fly. Something about these florida bass is making them freak out and freeze when caught. I'll try again and take a picture. Absolutely crazy.

Or Bath salts