Chet, there's a lot more I don't know about agricultural pesticide/herbicide effects on fish and fish-eater health than what I do know. I would not be surprised to find that much of what I do "know" is wrong. But let me run down a few things I'm fairly sure of.
1. The chemicals may build up or remain in sub-pond soils for a long time.
2. Any that enter the aquatic food chain tend to be in higher concentration as you move up the chain - invertebrates would have a low level, forage fish more, predator fish the most.
3. The chemicals are legal to use on crops
where their effects have been studied. The soy products you eat came from beans with chemicals used that (should have and I believe did have) had the effects of their residuals in the beans tested, and determined "safe" for the level expected to be present when harvested. But the affects they have on aquatic life downstream from the bean field is much less likely to have been studied, IMHO.
I would personally not be worried about the health of the fish - they're just fish. (What's that noise outside, why it's a mob of angry pondmeisters with pitchforks and torches, come for the heretic!
) So if I wasn't planning on eating any fish from the pond, it wouldn't bother me at all. If I was eating a few fish now and then (less than the local state guidelines for fish consumption, for example), I don't think I'd worry too much. If I liked to eat pond fish as much as I do (I'd eat BG twice a week if I could raise and catch enough), no way would I want a pond fed by a no-till farming watershed.
That's just my opinion and I'm no expert on ag chemicals. I'm not sure we have any here, if so I sure hope they'll post some info. We do have some real experts on aquatic chemicals, but I don't think most of those are also used in agriculture (although some are). Maybe our unofficial research librarian, ewest, can locate some published studiesof the effects of ag chemicals on fish???