Wow! I can't believe somebody would voluntarily put that in a pond. With that piece of info, that pond may be messed up for quite some time and I don't know if I would even want to eat the fish. If you send the sample to Texas A&M, make sure you let them know that it may have "accidentally" gotten some Karmex in it and maybe they can tell you if it is still present and how long it might take to biodegrade. You could probably also ask the Dupont website and maybe get an answer that way. Let us know how it turns out.

Water dries, rocks crumble, and trees die. The only thing that is eternal is the reputation we leave behind.
- Ancient Viking Proverb