The law of shechitah applies only to cattle, beasts, and birds (בהמה,
חיה and עוף); there is no commandment as regards the killing of
fish. Tradition supports this exception by reference to the distinction
made in Num. xi. 22: “Shall the flocks and the herds be slain (ישחט)
for them, to suffice them? or shall all the fish of the sea be gathered
together (יאסף) for them, to suffice them?” Although the latter term
(יאסף) is also used of quails (ibid. 32), no such inference is made
with regard to birds, because in ver. 32 the term יאסף is not
contrasted by ישחט; besides, the verb שחט is frequently applied in
the Law to birds, but never to fish. Comp. Babyl. Talm., Chullin, p.
27b.
There is this difference to be observed between בהמה on the one hand,
and חיה and עוף on the other. In the case of the latter two the
shechitah must be followed by the covering of the blood (כסוי דם Lev.
xvii. 13). The object of this law is, according to some, to prevent the
blood being used for idolatrous and superstitious purposes, as birds
and beasts were generally hunted in the fields, mountains, and woods,
places frequently associated in the imagination of the ancients with
evil spirits and the like. (Comp. Commentary of R. Obadiah Seforno on
the Pentateuch, ad locum.) The law was perhaps intended to impress the
lesson on the mind of the hunter that the blood shed of a living being
presents a ghastly sight that offends the eye of man. He will accustom
himself to think that taking away the life of another being, even of an
animal, is an act of grave responsibility, and will not be led to
misuse his weapons against any of his fellow-men.