Why Fish Require No Ritual Slaughter and How Creatures Were Formed

How do we know that fish do not require ritual slaughter? Shall we say it is from what is written, "Shall flocks and herds be slaughtered for them to suffice them, or shall all the fish of the sea be gathered for them?" (Numbers 11:22), meaning by mere gathering? But then, from "and they gathered the quail" (Numbers 11:32), should we likewise say that quail require no slaughter? They reply: there [regarding quail] gathering is not written in place of the slaughter of other creatures, whereas here [regarding fish] gathering is written in place of the slaughter of other creatures. Over the Galilean expounded: a beast, which was created from the dry land, its fitness for eating is by two signs [the slaughter of windpipe and gullet]; fish, which were created from the water, their fitness is by nothing at all; a bird, which was created from the mud [the mixture of water and earth], its fitness is by one sign. Rav Shmuel of Cappadocia said: know this, for birds have scales on their legs like fish. He further questioned him: "Let the waters swarm with swarms of living creatures, and birds" (Genesis 1:20) — evidently they were created from the water; yet it is written, "And the LORD God formed out of the ground every beast of the field and every bird" (Genesis 2:19) — evidently they were created from the earth. He said to him: they were created from the mud. He saw his students looking at one another. He said to them: Does it trouble you that I pushed off my adversary with a straw? They were created from the water — and why then were they brought to the man to give them names? And some say: in the first formulation he was speaking to his students, and in the latter formulation he was speaking to that governor, because it is written concerning "and He formed."