Nedarim, Chapter Six, Mishnah Four
This mishnah discusses vows of abstinence from types of fish.
1) [Konam,] if I taste fish or fishes, he is forbidden [to eat] them, whether large or small, salted or unsalted, raw or cooked.
a) But he may eat chopped terith and brine.
2) He who vows [abstinence] from zahanah is forbidden chopped terith, but may eat brine and pickled fish brine.
3) He who vows [abstinence] from chopped terith may not eat of brine and pickled fish brine.
Section one: If one forbids himself to eat either fish or fishes he is forbidden to eat all kinds of fish. Since he used both plural and singular, he clearly intended to forbid himself from all fish. However he may eat chopped terith, because that is not called fish. Although I dont know exactly what this was, I assume that it was so chopped up that people didnt really think of it as fish. He may also eat the brine, the liquid that comes out of fish (sounds gross to me, but certain members of my family do seem to enjoy this).
Section two: Zahanah is a foul-smelling mixture of different chopped fish, and hence one who vows not to eat zahanah, may also not eat chopped terith. However, he may still eat different types of brine.
Section three: Chopped terith includes in it brine and pickled fish brine. Therefore one who forbids himself from eating chopped terith may not eat any type of brine either.