Matsya was the first incarnation of Lord Vishnu in Satya Yuga and Matsya Jayanti is observed as the birth anniversary of Lord Vishnu.
Special Puja is performed in temples dedicated to Lord Vishnu. Matsya Jayanti day, which falls during Chaitra Navratri, usually coincides with Gangaur celebration.
Rituals, Significance of Matsya Jayanti / Birthday:
Matsya Avatar is the first avatar of Sri Maha Vishnu. As per legands, Sri Vishnu in the avatar of one-horned fish which saved the lives of Manu and the Saptarishis during the great flood. Bhagavan Sri Maha Vishnu has also rescued the Vedas from the demon and restored order to the Universe.
1) Fasting from the night before to the day after.
2) Before breaking the fast offer prayers to Sri Maha Vishnu and also offer bhog which is later distributes as Prasadam to the family and other people
3) Worshipping Sri Maha Vishnu is considered highly prosperous
4) Staying away at night and reciting Sri Maha Vishnu Sahasranma is very fruitful
5) Donating food to Brahmas is also very productive activity