List of halal and kosher fish
This is a list of fish that are considered both "halal" by Jaʽfari Shia Muslims and kosher by Jews according to "halakha". Criteria of inclusion. The Jafari Shia Islam rules are approximately equivalent to "kashrut" rules. The two are generally the least inclusive, and are used as the basis of this article: All fish in this article have true (visible) fish scales, an endoskeleton, fins, and gills (as opposed to lungs). The requirement for gills is not part of any religious rule, but biologically it is an identifying characteristic of true fish. Any animal  lacking any of the latter three features is not a fish, and is therefore not valid for this article. The rules are relaxed in some Islamic schools of thought, both Shia and Sunni. Some have looser definitions which include the exoskeleton of crustaceans as "scales", others yet include the softer exoskeletons of prawns as "scales" but exclude the harder exoskeletons of lobsters. They also differ in the definition of fish, some adopting a loose definition to include all water life ("sea game"). Kosher. According to the "chok" or divine decrees of the Torah and the Talmud, for a fish to  be declared kosher, it must have scales and fins. The definition of "scale" differs from the definitions presented in biology, in that the scales of a kosher fish must be visible to the eye, present in the adult form, and can be easily removed from the skin either by hand or scaling knife. Thus, a grass carp, mirror carp, and salmon are kosher, whereas a shark, whose scales are microscopic, a sturgeon, whose scutes can not be easily removed without cutting them out of the body, and a swordfish, which loses all of its scales as an adult, are all  not kosher. When a kosher fish is removed from the water, it is considered "slaughtered," and it is unnecessary to ritually kill it in the manner of kosher livestock. However, kosher law explicitly forbids the consumption of a fish while it is still alive. Fish with dairy. Although there is an opinion of Rabbi Yosef Karo of Safed (in his 16th century legal commentary, Beit Yosef) that milk and fish should not be cooked or eaten together, Karo references the Shulhan Aruch (OC 173:2) which actually deals with meat, and not fish. Most rabbinic authorities from that time onwards (including  almost all Ashkenazi ones) have ruled that this was a scribal error, and there is neither Talmudic basis nor any other rabbinical precedent for prohibiting milk and fish, and thus permit such mixtures. Indeed, two passages in the Babylonian Talmud implicitly state that it is entirely permissible. Nevertheless, since Karo wrote that milk and fish should not be mixed, there are those who do not mix them. The Chabad custom is not to eat fish together with actual milk, but to permit it where other dairy products are involved, so that adding a touch of butter or cream to the  milk is sufficient to permit mixing it with fish. Halal. Sunni. In Sunni Islam, there are two general schools of thought. Most Sunni Muslim schools of jurisprudence (Shafi'i, Hanbali, and Maliki) hold as a general rule that all "sea game" (animals of the sea) are permissible to eat with a few minor exceptions. Thus, for example, the local dish Laksa (which includes meats such as shrimp and squid with a soup base made from shrimp paste), is deemed permissible in the Shafi'i Sunni Muslim majority nations of Indonesia and Malaysia where it is commonly consumed. Hanafi. In the Hanafi school  of Sunni Muslim jurisprudence, to which the majority population of Sunni Muslims belong to, only "fish" (as opposed to all "sea game") are permissible, including eel and hagfish. Any other sea (or water) creatures which are not fish, therefore, are also "makrooh" whether they breathe oxygen from water through gills (such as prawns, lobsters and crabs which are crustaceans), mollusks such as clams, octopus, mussels and squid, especially if they breathe oxygen from air through lungs (such as sea turtles and sea snakes which are reptiles, dolphins and whales which are mammals, or semi-aquatic animals like penguins which are  birds, saltwater crocodiles which are reptiles, seals which are mammals, and frogs which are amphibians). Shia. Shia Islam allows for consumption of only fish that has scales, as any other water creature, with exception of edible crustaceans (i.e., lobster, shrimp, except crab), which are also Halal, other fish without scales are "haram" (forbidden).