In Europe, some take a scale from the carp eaten on Christmas and keep it in their wallet, in order to bring them luck and prosperity. Another belief is that a moon-shaped stone is located over the eye of a carp: The person who finds it on Christmas will have good luck.
Asia is the home of the valuable and beloved Koi carp. In Japan, they are a symbol of strength, as they are the only fish which can conquer the waterfalls of the Yellow River. Therefore a gift of a Koi is believed to grant the receiver strength.