The Kosher Status of Fish

Fish that have both scales and fins are Kosher; fish with only fins are non-Kosher. There are four types of scales: ctenoid, cycloid, ganoid and placoid. According to the law, only the first two types are Kosher. Ganoid scales are the type on a sturgeon, and placoid scales are the type on a shark. Unlike animal blood, fish blood is permitted, and no specific method of slaughter is required. The scales must be true scales that do not damage the skin when removed. As the law says, "Those fish with scales and fins are permitted to you..." (Vayikrah XI:9-12) Bony nodes, scutes and spiny scales damage part of the skin when removed, so they are not considered scales; thus eels, rays, sharks, sturgeons, swordfish and other fish with scutes are all non-Kosher.

Crustaceans and mammals such as sharks and dolphins are all non-Kosher. Only the roe of Kosher fish - that is, fish eggs - is permitted, so supervision is necessary. When buying fresh whole fish, fillets and frozen fish, one should be careful, because one may buy non-Kosher fish or fish contaminated by residue left on knives and cutting boards by non-Kosher fish. Fish sticks involve three aspects: the fish, the oil, and the frying facility (usually used for both Kosher and non-Kosher fish). Smoked fish is usually first soaked in brine and then smoked together with non-Kosher fish. According to Jewish law, the soaking and smoking process is equivalent to the process of roasting over fire, so such a product is non-Kosher. Smoked fish is also often coated with oil, which may not be Kosher. Although herring is a well-known Kosher food, it is not always Kosher. The production of herring may involve many Kosher issues, such as mono- and diglycerides, non-Kosher wine vinegar or wine, sour cream, breadcrumbs, spices and equipment contamination. The provider of the above Kosher and non-Kosher fish lists is Dr. James W. Atz, curator of the Department of Ichthyology at the American Museum of Natural History in New York and director of bibliography. We also thank Rabbi Genack and the Union of Orthodox Jewish Congregations of America for allowing us to reprint.