Nyaya – Fish and its bone.

मत्स्यकण्टकन्यायः

It originates from the fact that when a fish is caught, it is caught wits its bone, but when eating, only its flesh is retained, and bone is thrown out. It is used to denote the policy of a truly wise man who would observe everything in nature and would gather from it what conduces to his welfare and reject the rest.