Water-borne animals are broken down into two very broad categories: fish and shellfish. In the most general terms, fish are vertebrates with fins and gills; while shellfish are invertebrates, either having shells of one sort or another, or having evolved past the need for one. (For more details, see shellfish.)

• Fish are further separated into freshwater and saltwater fish. Because fresh water provides less buoyancy than salt water, freshwater fish have hundreds of tiny, light bones in a network throughout the flesh. Saltwater fish, on the other hand, have thicker, fewer bones, making them more attractive for eating.
• Fish are divided into three broad categories based on the fat content of their flesh: lean, moderate-fat and high-fat fish. In lean fish (e.g. flounder), the fat is concentrated in the liver rather than the flesh. The meat tends to be mild and lightly colored.  Moderate-fat fish have darker color, firmer texture and more assertive flavor than lean fish. High-fat fish (e.g. tuna) can average 12 percent fat, but some have fat contents up to 30 percent. These fish have the darkest color, firmest texture and most distinctive flavor.
• Fish are also categorized as flatfish or roundfish. Flatfish are adapted to swimming long the bottom of the sea or ocean. They are oval-shaped, with both eyes on the topside of the body, and are usually dark on the top and pale or white on the bottom. Roundfish have round or oval bodies, with eyes on opposite sides of the head.

For questions about buying, preparing or storing fish, call the free government-sponsored fish and shellfish hotline at 1.800.332.4010.

This large subclass of saltwater fish, encompassing some 500  species (130 available in the U.S.), includes popular varieties like flounder, halibut, sole and turbot. Most of these fish have sweet, delicate white flesh that chefs and consumers everywhere enjoy: low fat, fine-textured meat and mild flavor. All flatfish belong to the order Pleuronectiformes, which means they have both of their eyes on the same side of their head.

Any one of several species of large flatfish. In America, flounder is often sold as filet of sole, though the only true “filet of sole” is the imported Dover Sole (Solea solea), fished in the North Atlantic off Europe. All the flatfish fished commercially in the U.S. are really flounders. Alaska has the largest flounder resource in the world, capable of producing sustained landings of almost a million tons a year.

A common tropical fish found in most tropical waters but especially in the Caribbean. The name comes from its ability to soar through the air for great distances, sometimes up to a quarter of a mile. It has large pectoral fins to help ride the air after bursting from the water to evade predators. A small fish, it makes excellent food with a firm texture and mild flavor. Trivia: Flying fish figure prominently in Santiago’s survival in Hemingway’s “The Old Man and The Sea,” among other works of literature.

The delicate meat of the hind legs, the only edible part of a frog, is tender and lightly sweet. And, yes, as the old joke goes, they do taste like chicken—more specifically, they can be compared with the white meat of a very young chicken. Fresh frog’s legs can be found from spring through summer. Typically, they can be found in connected pairs, weighing from 2 to 8 ounces. Frozen frog’s legs can usually be purchased year-round in specialty markets.

Pronounced FOO-goo, this is the Japanese name for a pufferfish that contains a poison sac so toxic, a single fish contains enough to kill 30 adults. Approximately 100 people die every year of fugu poisoning. Yet, it’s still a delicacy in both Japan and the Philippines. In Japan, it is used in both sashimi and nabemono preparations, and only qualified chefs trained in removing the sac may prepare it. In Japan, it is eaten almost in a ritual, first with the fins being fried and served with sake (fugu hire-zake); then the skin is de-spiked and served on a salad (yubiki) with a ponzu dressing; and finally the flesh is sliced and served. Trivia: It is the only food not permitted to be served to the Emperor of Japan.