The Salmon figures prominently in the adventures of Fionn mac Cumhaill. According to the story, an ordinary salmon ate nine hazelnuts that fell into the Well of Wisdom (aka Tobar Segais) from nine hazel trees that surrounded the well. By this act, the salmon gained all the world's knowledge. Moreover, the first person to eat of its flesh would, in turn, gain this knowledge.
Salmon of Knowledge - Framed Bronze