SB 5.18.25
om namo bhagavate mukhyatamaya namah sattvaya pranayaujase sahase balaya maha-matsyaya nama iti.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
I offer my respectful obeisances unto the Supreme Personality of Godhead, who is pure transcendence. He is the origin of all life, bodily strength, mental power and sensory ability. Known as Matsyavatara, the gigantic fish incarnation, He appears first among all the incarnations. Again I offer my obeisances unto Him.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Srila Jayadeva Gosvami sings:
pralayo payodhi-jale dhrtavan asi vedam
vihita-vahitra-caritram akhedam
kesava dhrta-mina-sarira jaya jagad-isa hare
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 first 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 sattvaya is used here, meaning pure goodness on the transcendental platform. There are many incarnations of the Supreme Lord: Varaha murti (the boar form), Kurma murti (the tortoise form), Hayagriva murti (the form of a horse) and so on. Yet we should never think any of Them material. They are always situated on the platform of suddha-sattva, pure transcendence.