A kipper, also known as a red herring, is a whole fish that has been split from tail to head, eviscerated, salted, and cold smoked. Typically, the species is a herring or salmon, but traditionally it is any fish found in great numbers and caught during its spawning period. The process of smoking the fish turns it red. Spawning fish are not good to eat fresh and usually arrive in great abundance, thus they are salted and smoked to improve flavor and preservation.
http://en.wikipedia.org/wiki/Kipper