During the current kalpa (day of Brahma), Matsya appeared during the first manvantara (Svayambhuva) about 2 billion years ago and then again at the end of the sixth manvanatara (Caksusa) several hundred thousand years ago. We are currently in the seventh manvantara (Vaivasvata).

In both cases he appeared at the time of a devastation - the first time after a night of Brahma (kalpa) and the second after a manvantara. His mission in the first case was to protect the Vedic mantras (from the demon Hayagriva) and to restore them to Lord Brahma for dissemination throughout the universe. More widely known is, however, His other pastime in appointing King Satyavrata to protect the seeds of all creatures on a boat from the flood to allow recreation in the next age. Therefore, it was Sri Matsya who facilitated the subsequent creation at the end of each devastation. In fact, Sri Rupa Gosvami mentions in his Laghu-bhagavatmrta 1.3 that Sri Matsya appears at the end of every manvantara for a similar mission.

One of the 18 Maha Puranas ( Primary ) is the Matsya Purana.

Soon after the cosmic creation, the entire universe was inundated with water. At that time Lord Krsna (Kesava) incarnated as a gigantic fish to protect the Vedas. Therefore Manu addresses Lord Matsya as mukhyatama, the lila incarnation to appear. Fish are generally considered a mixture of the modes of ignorance and passion, but we must understand that every incarnation of the Supreme Personality of Godhead is completely transcendental. There is never any deterioration of the Supreme Lord’s original transcendental quality. Therefore the word sattväya is used here, meaning pure goodness on the transcendental platform.