Valmiki Ramayana Bala Kanda Sarga 14 Shloka 29

तदा then, शामित्रे तु in the act of killing animals, तत्र there, हय: horse, तथा and, ये other, जलचरा: aquatic animals, एतत्सर्वम् all these, ऋत्विग्भि: by chief priests, शास्त्रत: in accordance with tradition, नियुक्तम् tied up.

When the time came to sacrifice the animals, the chief priests, in accordance with tradition, tied up the horse and all the aquatic animals to the sacrificial posts.