Halakhah zu Wajikra 11:29

As formulated in Leviticus 11:10, the prohibition against forbidden aquatic creatures reads: "And all that do not have fins and scales in the seas and in the rivers, of all that creep in the waters and of all living creatures that are in the water, they are detestable unto you." The Gemara, Hullin 66b, declares that the requirement that aquatic creatures have fins and scales as a condition of dietary acceptability is limited to those that spawn in "the seas and in the rivers" and hence creatures that spawn in stagnant pits or utensils are permissible. The Gemara, Hullin 67a, qualifies that exclusion in indicating that creatures that spawn in utensils are permissible only so long as they remain in their aquatic element. Upon emerging, or upon being removed, from water they acquire the forbidden status of "creeping things that creep upon the earth" (Leviticus 11:29) and remain prohibited even if they return to the water from which they emerged. Thus, insects that spawn in stagnant water collected in stationary cisterns or the like are not forbidden unless they become separated from the water that is their natural habitat.

The commandment of the impurity of the eight swarming creatures: That the eight swarming creatures are impure and render impure, as it is stated (Leviticus 11:29), "And this shall be impure for you from the swarming creatures that swarm on the ground: the mole, the mouse and the lizard, etc."