Fermented fish sauce
Cuisines around the world use various forms of fermented fish sauce as a condiment or ingredient. The details of preparation can be unpalatable to some, but they basically involve fermenting seafood in salt, and obtaining distinctively flavored extracts. While they are primarily flavorings, they also can have a high protein, as well as sodium, concentration
While many think of this as an Asian flavoring, garum was a basic element of cooking in the Roman Empire, and the very British Worcestershire sauce has fermented anchovies as one of its core components, although tamarind is another part of its distinct taste.
Southeast Asian kitchens and tables, however, are bare without fish sauce. The basic Vietnamese term is nuoc mam, but that is somewhat like saying "wine" in France; there are many distinctive preparations, and indeed some premium forms that are labeled to their place of origin. In Thai cuisine, the term is nam pla, also called "fish soy." The Burmese version is ngan-pya-ye and the most common Filipino name is batis.
Not strictly fish, but some related preparations, these more from Asia, are sauces, pastes, or dried forms of fermented shrimp. Oyster sauce is a Chinese ingredient made from fermented shellfish, and Korean kimchi recipes often include oysters or shrimp: fresh, fermented, or dried.
Some American veterans of the Vietnam War brought back unpleasant memories, perhaps embellished with memories and storytelling, of reeking nuoc mam. Other Americans, however, routinely use it and find it has only a slight smell, but potent flavoring properties different from fermented soy.