as far as I'm aware it is allowed, halal and kosher being mostly the same rules. no pork no shellfish for health reasons rather than religious ones
there might be localised variants but malaysia is a muslim conglomerate and they thrive on fish. I know my neighbours eat fish and I've had jokey discussions about preparing anchovies properly. in birmingham where I go a lot all the chippies are owned by muslims who if it was unclean wouldnt be there.
it needs updating but the rules are there more to show discipline in your faith.
Apparently Mohammed liked fish too much to steal that law from the Jews.
P.S. Kosher is NOT the same as hallel. Jews are not permitted to eat Hallal because Halal is not prepared according to Torah law. Halal is not of the higher standards of Torah law and Kosher.
the quran says to the more or less meaning to not eat anything with claws that need to defend themselves and use the claw for prey, like big cats, birds and such. we can eat fish becaue for one its healthy for us and two it dont have claws, for 3 it doesnt say not to.