Kashrut
Among the numerous laws that form "kashrut" are prohibitions on the consumption of certain animals (such as pork and shellfish), mixtures of meat and milk, and the commandment to slaughter mammals and birds according to a process known as "shechita". There are also laws regarding agricultural produce that might impact the suitability of food for consumption.
Smoked fish
Most other smoked fish in the US is hot-smoked, although cold-smoked mackerel is always available in East-European delis, along with cold-smoked sturgeon, sea bass, halibut or turbot and many other varieties. Jewish delis often sell, in addition to lox, hot-smoked whitefish, mackerel, trout, and sablefish (also sometimes referred to as black cod in its fresh state). Along the Mississippi River, hot-smoked locally caught sturgeon is also available. Traditionally, in the US, cold-smoked fish, other than salmon, is considered "raw" and thus unsafe to consume without cooking. For this reason, in the US, cold-smoked fish is largely confined to specialty and ethnic shops.