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.
Swordfish
Swordfish are classified as oily fish. Many sources, including the United States Food and Drug Administration, warn about potential toxicity from high levels of methylmercury in swordfish. The FDA recommends that young children, pregnant women, and women of child-bearing age not eat swordfish. (See mercury in fish for more details.)