And some official JW comments on the matter:
*** w73 4/1 p. 224 Questions From Readers ***
Questions From Readers
? Must fish be bled before they are eaten?—U.S.A.
The Bible does not specifically mention the bleeding of fish. Only in the case of land animals or fowl do we read: “As for any man . . . who in hunting catches a wild beast or a fowl that may be eaten, he must in that case pour its blood out and cover it with dust.”—Lev. 17:13.
Fish that were suitable for food according to the terms of the Mosaic law did not contain a quantity of blood sufficient to be poured out and covered with dust. Evidently for this reason the Law set forth no precise statement about bleeding fish.
There being no Scriptural stipulation to squeeze or soak meat to remove blood, no one is under obligation to take extreme measures to extract blood from fish. Of course, the blood of every sort of creature represents its life and is therefore sacred. So, if, on cutting a fish open, a person sees an accumulation of blood, he should remove it.
*** w61 11/1 p. 670 Questions From Readers *** ? In view of the Bible command on abstinence from blood, how are fish and insects to be prepared in order to be acceptable for food?—B. F., U.S.A. Fish was a common food among the Jews. Jesus himself ate it, and on different occasions he directed successful fishing operations, both with a net and with a hook. (Num. 11:5; Matt. 14:17; 17:27; Luke 5:1-11; 24:42, 43) Some insects, too, were used for food. (Lev. 11:21; Mark 1:6) Of course, the amount of blood contained in these creatures may be very small, so that it is impossible to pour out their blood; yet that is what was required to make the meat of a creature acceptable for food. (Lev. 17:13) It was not required that the meat be squeezed or that it be soaked; simply that the blood be poured out. If there is not enough blood to pour it out, Christians are not under obligation to take extreme measures to be sure that some blood is extracted. Of course, if, on cutting the creature open, an accumulation of blood is clearly in evidence, this can easily be removed, and it would be proper to do so.
*** w54 5/1 p. 287 Questions From Readers *** Basing our position on the Bible, we shall have a balanced view, neither fanatically opposing all killing of animals, nor wantonly hunting them for sport. Jesus ate meat, both fish and lamb. He directed a successful fishing operation using a net, and also instructed that a fish be caught with a hook. (Luke 24:42, 43; Ex. 12:3, 8; Matt. 26:17-21; Luke 5:4-6; Matt. 17:27) Apparently fish required no special attention in bleeding, since there is no instruction concerning them; but the requirements relative to game birds and animals are specific and must be followed by theocratic hunters seeking to vary their meat diet with some wild game. Bullet wounds of today, like arrow wounds or fang-and-claw wounds from beasts of prey during the time of application of the Mosaic law, seldom effect adequate drainage of blood. Hence the hunter must make it complete by using his knife, whether it spoils a trophy or not.