What is it about Tadpoles that Fish don’t like? I went collecting today and caught a nice size Rock Bass, and some other stuff. I also caught a few Bullfrog Tads. The Rocky went after a Tadpole, caught it and just as fast as it caught it spit it out. What’s up? I have yet to see a fish eat a Tadpole.

I spend a lot of time observing tadpoles, and even have a child's swimming pool outside my front door with wild spring peepers (Pseudacris crucifer) singing away right now. It is overloaded with their tadpoles at the moment but they are still going.

Yes, many tadpole species, mainly Rana and Bufo which breed in permanent bodies of water, produce chemical deterrents to fish predation. The Bufo even maintain these toxic skin secretions into adulthood to fend off reptile and mammal predation as frogs. That is what the gland on their head is for. The main predators of these tadpoles is predatory larvae, such as dragonfly larvae which can also predate on fish. Rana can take multiple years to metamorphose, depending on food supply, while surviving in water where large mouth bass and other large predatory fish are present.

Here is the abstract of a study considering whether toxic tadpoles species conferred any survival advantage to more palatable tadpole species:
http://www.nd.edu/~u...nontadpoles.pdf

Abstract. Anuran larvae that develop in permanent ponds often have strong chemical deterents that make them unpalatable or toxic to fish predators. Members of the Genus Bufo are well known for having these toxins. Conversely, western chorus frogs (Psuedacris triseriata) reproduce in ephemeral ponds and are palatable to fish predators. Yellow perch (Perca americanus) prefer chorus frog tadpoles and will learn learn to avoid American toad (Bufo americanus) tadpoles. This suggest that the presence of unpalatable toad tadpoles confer no survival advantages to palatable frog tadpoles.

I know of some local areas where 30% to 40% of the Rana tadpoles have a fair amount of their tail sniped away. I do not know whether this is from small fish, crayfish, or predatory larvae, as I have never seen it occur in spite of many hours watching day and night. Likely the latter though. Nor why some escape tail damage which does not appear based on size, thus presumably age. I suspect it is the result of variations in response to predatory cues. Tadpoles will respond to chemical cues tipping them off to the presents of predators, such as dragonfly larvae, and go into flight mode. The response can be artificially triggered in the lab by applying the chemicals. This tail loss is costly as a newly metamorphosed frog depends on this tail as its food source the first days of its life as a frog.