SB 5.18.24
ramyake ca bhagavatah priyatamam matsyam avatara-rupam tad-varsa-purusasya manoh prak-pradarsitam sa idanim api mahata bhakti-yogenaradhayatidam codaharati.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Sukadeva Gosvami continued: In Ramyaka-varsa, where Vaivasvata Manu rules, the Supreme Personality of Godhead appeared as Lord Matsya at the end of the last era [the Caksusa-manvantara]. Vaivasvata Manu now worships Lord Matsya in pure devotional service and chants the following mantra.