Leviticus 11:9-10, 12

“These you may eat, of all that are in the waters. Everything in the waters that has fins and scales, whether in the seas or in the rivers, you may eat. But anything in the seas or the rivers that does not have fins and scales, of the swarming creatures in the waters and of the living creatures that are in the waters, is detestable to you.

Everything in the waters that does not have fins and scales is detestable to you.