Shrimp

V

Types of Shrimp

True shrimp belong to the order Decapoda—a group containing crustaceans that have ten walking legs. In the marine waters of the United States, three of the most common commercial species are the pink shrimp, the brown shrimp, and the white shrimp. Found in the waters along the East Coast and in the Gulf of Mexico, these shrimp have a maximum length of about 20 cm (8 in). On the West Coast, the Franciscan Bay shrimp is caught commercially.

Freshwater shrimp are most common in warm parts of the world. They include river shrimp, edible shrimp that are trapped or farmed in the tropics, and also all true shrimp that have become adapted for life in caves. Cave shrimp are typically pale, with vestigial (nonfunctioning) eyes, and they find their way mainly by touch.

Decapod shrimp also include animals that are rarely eaten by humans. Among the most specialized are pistol shrimp, also known as snapping shrimp, which grow to 6 cm (2.4 in) long. These shrimp have a pair of enlarged pincers, one of which can be almost as long as the rest of the animal’s body. The pincer can snap shut, creating a shock wave that is powerful enough to stun small fish. Some pistol shrimp form mutually beneficial partnerships with fish called gobies. A pistol shrimp shares its food with the goby and digs a burrow for it on the seabed. In turn, the goby warns the pistol shrimp of a predator's approach, at which point both will hide in the burrow.

Many other crustaceans are commonly called shrimp, but they are not members of the order Decapoda. They differ from true shrimp in their anatomy and in their ways of life. These animals include tadpole shrimp, which breed in temporary pools in deserts, and brine shrimp, which live in salt lakes. Mantis shrimp are often caught in shrimp nets. They have a pair of strong grasping legs that can painfully wound fishermen who handle them carelessly. Mantis shrimp are larger than most true shrimp, measuring up to 56 cm (22 in) long.

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VI

Shrimp and Humans

Humans have eaten shrimp for centuries, and shrimp are a traditional ingredient in many regional cuisines. Shrimp meat is high in protein but low in fat, which makes it a highly nutritious food.

Each year in the United States, more than 125,000 tons of shrimp are caught, while the worldwide total is nearly 3 million tons. At sea, shrimp are usually caught by trawlers, motorized boats that drag pouched-shaped nets over the seabed. In the United States, shrimp harvesting occurs mostly along the southeastern coast and in the Gulf of Mexico, where the shallow seabeds provide good shrimping grounds. Farmed shrimp are raised from eggs, typically in tropical coastal ponds. This method of raising shrimp developed in the Asia, but it is now widespread throughout the tropical world. Farmed shrimp currently make up between a third and a half of all shrimp that enter the market.

Shrimp breed rapidly, which helps them to withstand annual harvesting. Even so, shrimp fishing has its limits, and there are signs of overharvesting in some parts of the world. In addition, because shrimp fisheries trawl the seabed, other animals are often caught in the nets–turtles are particularly at risk.

Shrimp farming also can cause environmental problems. In many parts of the tropics, mangrove swamps are cleared to make room for shrimp farms, removing habitats that are important breeding grounds for fish. Many shrimp farms are also short-lived—in some regions, disease and pollution limit their working life to as little as five years.

VII

Scientific Classification

True shrimp belong to the order Decapoda. The Sargassum shrimp is a member of the family Palaemonidae. It is classified as Leander tenuicornis. In the family Penaidae, the pink shrimp is classified as Penaeus duorarum, the brown shrimp is Penaeus aztecus, and the white shrimp is Penaeus setiferus. The Franciscan Bay shrimp is a member of the family Crangonidae and is classified as Crangon franciscorum. The river shrimp is a member of the Palaemonidae family and is classified as Macrobrachium carcinus.