98:15 The cord that is on a bird’s feet may be cut or burned off after the bird is slaughtered. It is permitted to sew poultry when stuffing them but one must be sure to thread the needle before yom tov. If one didn’t do so before yom tov, he may not do so on yom tov. After it was sewn, one may burn the leftover thread (or even cut it since this could not have been done before yom tov – Mishnah Brurah 509:18).
98:16 Regarding fish in a pond, if it is not possible to catch them by hand, only with a vessel, then they may not be caught on yom tov. If it is possible to catch them by hand, then one may catch them, even with a vessel. If there are many fish in the pond, one must select before yom tov the ones that he wants to take on yom tov; he should make some kind of a sign. If he needs all of them, he should select them all by saying before yom tov, “I am selecting all of these fish for yom tov.” (One may not catch fish from a river in any event – MB 497:1.)