Kosher Animals - Fish and Seafood

Fish and Seafood

Leviticus 11:9-12 and Deuteronomy 14:9-10 both state that anything residing in "the waters" (which Leviticus specifies as being the seas and rivers) is ritually clean if it has both fins and scales, in contrast to anything residing in the waters with neither fins nor scales. The latter class of animals is described as ritually impure by Deuteronomy, but Leviticus is much harsher, describing them as filth. (Hebrew: sheqets, sometimes translated as abomination; "abomination" is also sometimes used to translate piggul and toebah). Although these biblical rules do not specify the status of animals in the waters with fins but no scales, or scales but no fins, it has traditionally been assumed that these animals are also excluded from the ranks of the ritually clean.

These rules restrict the permissible seafood to stereotypical fish, prohibiting the unusual forms such as the eel, lamprey, hagfish, and lancelet. In addition, these rules exclude non-fish marine creatures, such as crustaceans (lobster, crab, prawn, shrimp, barnacle, etc.), molluscs (squid, octopus, oyster, periwinkle, etc.), sea cucumbers, and the cnids (jellyfish etc.). Other creatures living in the sea and rivers that would be prohibited by the rules, but are not normally considered seafood, include the cetaceans (dolphin, whale, etc.), crocodilians (alligator, crocodile etc.), sea turtles, sea snakes, and all amphibians.

Sharks are sometimes regarded as being among the ritually unclean foods according to these regulations, as they appear to have a smooth skin. However, sharks do have scales, they are just placoid scales, which are denser and appear smooth if rubbed in one direction, in contrast to leptoid scales, ganoid scales, and cosmoid scales. The sturgeon, and related fish, are also sometimes included among the ritually impure foods, as their surfaces are covered in scutes, which are bony armoured nodules; however, fish scutes are actually just hardened and enlarged scales. Scales has thus been traditionally interpreted along the lines of Nahmanides's proposal that qasqeseth (scales) must refer specifically to scales that can be detached, by hand or with a knife, without ripping the skin. In practice this excludes all but cycloid and ctenoid scales. A minor controversy arises from the fact that the appearance of the scales of sturgeon, swordfish, and catfish is heavily affected by the ageing process - their young satisfy Nahmanides' rule, but when they reach adulthood they do not.

Traditionally fins has been interpreted as referring to translucent fins. The Mishnah claims that all fish with scales will also have fins, but that the reverse is not always true. For the latter case, the Talmud argues that ritually clean fish have a distinct spinal column and flatish face, while ritually unclean fish don't have spinal columns and have pointy heads, which would define the shark and sturgeon (and related fish) as ritually unclean. Nevertheless, Aaron Chorin, a prominent 19th-century rabbi and reformer, declared that the sturgeon was actually ritually pure, and hence permissible to eat. Many Conservative rabbis now view these particular fish as being kosher, but most Orthodox rabbis do not. The question for sturgeon is particularly significant as most caviar consists of sturgeon eggs, and therefore cannot be kosher if the sturgeon itself is not. Sturgeon-derived caviar is not eaten by some Kosher-observant Jews because sturgeon possess ganoid scales instead of the usual ctenoid and cycloid scales. There is a kosher caviar made of seaweeds. The salmon roe is also kosher.