The term shrimp is used to refer to some decapod crustaceans, although the exact animals covered can vary. Used broadly, it may cover any of the groups with elongated bodies and a primarily swimming mode of locomotion – chiefly Caridea and Dendrobranchiata. In some fields, however, the term is used more narrowly, and may be restricted to Caridea, to smaller species of either group, or to only the marine species. Under the broader definition, shrimp may be synonymous with prawn, covering stalk-eyed swimming crustaceans with long narrow muscular tails (abdomens), long whiskers (antennae) and slender legs. They swim forwards by paddling with swimmerets on the underside of their abdomens. Crabs and lobsters have strong walking legs, whereas shrimp have thin fragile legs which they use primarily for perching.
Shrimp are widespread and abundant. They can be found feeding near the seafloor on most coasts and estuaries, as well as in rivers and lakes. To escape predators, some species flip off the seafloor and dive into the sediment.They usually live from one to seven years. Shrimp are often solitary, though they can form large schools during the spawning season. There are thousands of species, and usually there is a species adapted to any particular habitat. Any small crustacean which resembles a shrimp tends to be called one.
They play important roles in the food chain and are important food sources for larger animals from fish to whales. The muscular tails of shrimp can be delicious to eat, and they are widely caught and farmed for human consumption. Commercial shrimp species support an industry worth 50 billion dollars a year, and in 2010 the total commercial production of shrimp was nearly 7 million tonnes (see production chart on the right). Shrimp farming took off during the 1980s, particularly in China, and by 2007 the harvest from shrimp farms exceeded the capture of wild shrimp. There are significant issues with excessive bycatch when shrimp are captured in the wild, and with pollution damage done to estuaries when they are used to support shrimp farming. Many shrimp species are small as the term shrimp suggests, about 2 cm (0.79 in) long, but some shrimp exceed 25 cm (9.8 in). Larger shrimp are more likely to be targeted commercially, and are often referred to as prawns, particularly in Britain.
What's New and Beneficial About Shrimp
- Shrimp are an unusually concentrated source of the antioxidant and anti-inflammatory nutrient called astaxanthin. It's not unusual for a single 4-ounce serving of shrimp to contain 4 milligrams of astaxanthin. Astaxanthin is a carotenoid that is receiving special attention in the latest health research, primarily for its anti-inflammatory and antioxidant properties. Release of inflammatory messaging molecules (like tumor necrosis factor alpha and interleukin 1B) is suppressed by astaxanthin, and so is unwanted oxidation of fats in immune cells. In animal studies, risk of colon cancer is lowered by intake of astaxanthin, and immune-related problems of diabetes are also reduced. It's the antioxidant and anti-inflammatory properties of astaxanthin that seems to explain these disease-related benefits. Since few commonly consumed fish (with the exception of salmon) can provide us such concentrated amounts of astaxanthin, shrimp may be making a unique health contribution in this way.
- At 56 micrograms in every 4 ounces, shrimp is an excellent source of the antioxidant mineral selenium. Recent research studies show that the selenium contained in shrimp can be well-absorbed into the human body. In one study, we've seen an estimate of about 80-85% for total selenium absorption from this shellfish. Since selenium deficiency has been shown to be a risk factor for heart failure and other forms of cardiovascular disease, as well as for other problems including type 2 diabetes, compromised cognitive function, and depression, shrimp may have a unique role to play in your meal plan if your health history places you at special risk in any of these areas.
- Shrimp is often included on the "avoid" list for persons wanting to minimize their dietary intake of cholesterol. The 220 milligrams of cholesterol contained in a 4-ounce serving of shrimp makes this approach a legitimate concern. However, despite its high cholesterol content, several recent research studies have noted some desirable aspects of the fat profile in shrimp. One of these desirable aspects is shrimp's omega-3 fat content. Four ounces of shrimp provides about 350-375 milligrams of omega-3 fatty acids, including about 50% EPA (eicosapentaenoic acid) and 50% DHA (docosahexaenoic acid). EPA and DHA are especially important omega-3s for cardiovascular and nervous system health. In addition to this great mixture of omega-3s, shrimp also provides an outstanding ratio of omega-3:omega-6 fats. There are approximately three times as many omega-3s as omega-6s in shrimp. Since higher ratios of omega-3:omega-6 are associated with decreased risk of many chronic diseases—including obesity, high blood pressure, and type 2 diabetes—this aspect of shrimp's fat content is a huge plus. Finally, it is interesting to note that according to recent studies, cholesterol is not the only sterol in shrimp. This type of fat is found in smaller amounts in the form of beta-sitosterol, campesterol, and brassicasterol. While chemically similar to cholesterol, these other sterols function as anti-inflammatory molecules and they are associated with decreased levels of LDL-cholesterol, which would be considered a health benefit by many researchers. When looked at from this broader perspective, risks related to the high cholesterol content of shrimp might be overshadowed by its omega-3 and sterol composition—but we will need future studies to help us understand more about the big picture involving shrimp and fat. As always, if you have concerns that have you need to be cautious about cholesterol intake, discuss the inclusion of shrimp in your diet with your healthcare practitioner.
- If you are planning to eat wild-caught, cold-water shrimp, the Monterey Bay Aquarium Seafood Watch has determined that your best overall choices in this category of shrimp are British Columbia spot prawns, California coonstripe shrimp (caught using submerged pots), and Oregon pink shrimp. (You probably won't be able to tell from a label whether your shrimp have been pot-caught, so you will need to talk to your fishmonger or the fishery itself in order to determine this information.)
- If you are concerned about environmental consequences when consuming farmed shrimp, the Monterey Bay Aquarium Seafood Watch recommends that you restrict your intake to shrimp that have been raised in a fully re-circulating system. These systems make direct use of filtered seawater or try to recreate the mineral composition of seawater in freshwater. (You will often need to contact the supplier in order to determine whether this type of farming system was used.) Pacific white shrimp (Litopenaeus vannamei) can make an excellent choice when farmed in this way.
- While U.S. farmed, freshwater shrimp are not widely available in the marketplace, they are also recommended by the Monterey Bay Aquarium Seafood Watch as a Best Choice when choosing shrimp.