CRUSTACEANS AND SHELLFISH

CRUSTACEANS AND SHELLFISH. The crustaceans are not, strictly speaking, shellfish, although they are often described as such. They are members of the animal phylum Arthropoda, which also includes spiders, scorpions, and insects. Like these other creatures they are covered with hard, horny carapaces which are jointed for movement and sloughed from time to time as their owners grow. Many have a characteristic change of color when cooked, for example the blue-black lobster turns scarlet and the semitransparent shrimp turns pink and white.

The two principal orders are Decapoda Natantia and Decapoda Reptantia, that is to say, "ten-legged swimmers" and "ten-legged crawlers." In the first category are prawns, shrimp, lobster, and so on. The second consists of the crabs.

Prawns and Shrimp

The terms "prawn" and "shrimp" require a little explanation since the two terms are used in different ways in British and American English. The FAO (Food and Agriculture Organization of the United Nations) in their comprehensive Catalogue of Shrimps and Prawns of the World (1980), describes the differences in useage as follows:

we may say that in Britain the term 'shrimp' is the more general of the two, and is the only term used for Crangonidae and most smaller species. 'Prawn' is the more special of the two names, being used solely for Palaemonidae and larger forms, never for the very small ones. In North America the name 'prawn' is practically obsolete and is almost entirely replaced by the word 'shrimp' (used for even the largest species, which may be called 'jumbo shrimp'). If the word 'prawn' is used at all in America it is attached to small species.

The smallest shrimp are of considerable interest in regions such as Southeast Asia where they are eagerly collected to be fermented and made into shrimp paste, most notably in the Philippines, where it is known as patis, and also Malaysia and Indonesia, where it is blachan. Use of these products is less widespread than the ubiquitous Southeast Asian fish sauces, but they too make a significant contribution to the diet in the countries where they are made. In Europe, especially Britain, small shrimp may also be made into a paste, but without fermentation and packed in small jars as a delicacy for the tea table. Delicate shrimp paste sandwiches are considered a real treat. It is also possible in England to buy potted (cooked and packed in butter) shrimps from Morecambe Bay, a traditional preparation which has cultural overtones, being perceived as part of the British culinary heritage and identity. In North America the very smallest shrimps attract little interest, and it is the larger species such as the brown shrimp (Penaeus aztecus aztecus ) and the white shrimp (Penaeus setiferus ) which are most prominent in the markets. In Europe , the counterpart of these species is the socalled deep water prawn (also known as northern prawn, Pandalus borealis ; but this is not exclusive to Europe, being found also in the North Atlantic from Greenland down to Martha's Vineyard).

Large shrimp, especially species of the genus Macrobranchium which thrive in brackish or fresh water, are now the subject of aquaculture in Southeast Asia, and the large quantities exported from there go a long way to meeting demand in Europe. Large shrimp are often presented on their own (for example boiled and then served cold with mayonnaise, or broiled), while smaller ones may be used to make the shrimp croquettes which are a particularly successful dish in the Netherlands and Belgium, or a shrimp sauce or shrimp soup.

Large shrimp in the Mediterranean belong to various species which resemble each other so closely that sometimes it is only an expert who can distinguish between them. One of the best is Penaeus kerathurus, the Italian mazzancolla. It may reach a length of 22 cm/9 inches, which is large for the Mediterranean but well short of 33 cm/13 inches, the maximum length of the Giant Tiger prawn of the Indo-Pacific, Penaeus monodon.

Lobsters

Lobsters are larger creatures, although the smallest of the the so-called Norway lobsters (often referred to by the Italian name scampi), are no bigger than the largest prawns. The archetypal lobster, that of the North Atlantic, is not one but two species, having developed in slightly different forms on the two sides of the ocean. The American lobster, Homarus americanus, attains a somewhat greater size than its European counterpart, H. gammarus. However, the whole question of maximum sizes has become one where precision is difficult to attain. The fishery for lobsters is now so intensive that few or none approach the maximum size recorded in the past. It is generally accepted that a specimen taken off the coast of Virginia in the 1930s holds the record; it measured more than a meter (3′ 3″) in length and weighed about 20 kg/45 lb. No lobster of comparable size has been taken since World War II. In any case, there is no special merit, for consumers, in great size.

The value of lobsters in the market is considerable, but the supply of adult lobsters from the wild is limited. One reason is that only certain types of seabed are suited to tiny postlarval lobsters. If they don't make it to a suitable place, they perish. Also, competition among lobster fishermen is intense. So, as long ago as the beginning of the twentieth century experimental lobster "farming" was being conducted in a number of countries.

Where lobsters are "farmed," one procedure is to raise them from fertilized eggs, keeping each tiny creature in its own compartment to prevent it from being eaten, and then releasing them into the wild when they are large enough to have a good chance of survival before they reach the minimum weight at which it becomes legal to catch them. This is generally around 450 to 500 grams (just over a pound). The alternative procedure involves keeping the lobsters in captivity until ready for sale. One advantage of this is that the fully "farmed" lobster may be sent to market at a weight of only about 250 g (half a pound) and will have attained that weight relatively quickly (further growth being slower). There is a large and growing literature on all this, whether conducted by institutions to increase stocks in the wild for the general benefit or by private "farmers" for their own profit.

The red color of a cooked lobster is intense and dramatic; it has been compared to that of a cardinal's hat. However, this cannot rival the amazingly bright and complex colorations of the "spiny lobsters," also known as crawfish, which belong to warmer and tropical waters. Lobsters in this other category are, some would say, not true lobsters. They lack the large claws of the Atlantic species, and hence have less meat, but they grow to a good size and are greatly appreciated as food. They too are "farmed," on an increasing scale. Palinurus elephas is one of several species that are present in the Mediterranean, while Panulirus argus is the most prominent in American waters. (The designations are confusing. The genus Palinurus has been recognized since the late eighteenth century, but it seems not to have occurred to the naturalist who created Panulirus halfway through the nineteenth century that he was sowing seeds of confusion by his choice of name.) The spiny lobsters of Asian waters include the remarkably beautiful Panulirus ornatus and P. versicolor (see illustration).

There are other "lobsters," of different shape, classified in the family Scyllaridae and going by names such as "flat lobster" and "slipper lobster." One, Thenus orientalis, has achieved fame and a certain cultural status in Australia, where it is the "Moreton Bay bug," a name which combines an Australian geographical identifier with an indication of Australian plebeian insouciance.

Crabs

Most Europeans, invited to think of a crab, would have a mental picture of Cancer pagurus, the common crab of European temperate waters. North Americans would picture the famed blue crab of Chesapeake Bay and other parts of the eastern seaboard; or, if belonging to the western coast, the Dungeness crab. These three important species all share the familiar, compact, wide-bodied and big-clawed shape, and all are excellent tasting. The blue crab is, at least for east coast Americans, a cultural as well as a gastronomic phenomenon. The annual crab-picking "derby" at Crisfield, Maryland, is a symptom of its status. However, its reputation rests more on the fact that it is the crab which, when it has moulted and before the new hard carapace is grown, provides the basis for the soft-shell crab industry.

In waters that are either much colder or much warmer, crabs take on a different aspect. In the icy waters of the Arctic there is a vigorous fishery for two kinds of crab with extraordinarily long and thin legs, the snow crabs of the genus Chionocoetes and the king (or red) crab Paralithodes camtschatica. Their meat, which is of excellent quality, is usually frozen or canned, since the fishing grounds are so remote that it would be impracticable to do otherwise.

In tropical waters, on the other hand, there is a great diversity of swimming crabs and others, often brightly colored. Some spend some time on land, for example the large land crabs that are appreciated in the francophone West Indies and, in the Indo-Pacific region, the red crabs of Christmas Island and the robber crabs, which climb coconut trees and steal the nuts.

Crayfish

Although most edible crustaceans come from the sea, there are two important freshwater families, those of the crayfish (the family Astacidae in the northern hemisphere, and Parastacidae in the southern hemisphere). One interesting feature of the whole group of crayfish is that their distribution in the world is surprisingly, one might almost say inexplicably, patchy. Except for Papua New Guinea, there are none in the tropics. They are absent from most of Asia and are only found in two habitats in South America, yet there are over 250 species in North America. Europe has seven species and East Asia has four. Of the 120 species in the Southern Hemisphere, 110 are Australasian. They all resemble each other quite closely, but vary considerably in size and edibility. The largest is the giant Tasmanian crayfish, which may be 60 cm (two feet) from head to tail and may weigh as much as 4.5 kg (10 lb). Others are so small (2 cm / ¾ inch) in length that they are of no interest except perhaps as bait.

Habitats vary. There are aquatic crayfish living in rivers or streams; semiaquatic species that live out of water in burrows connected by shafts to a body of water; and the tiny land crayfish, which live on land but only on land that has water underneath it.

Enthusiasm for crayfish is greatest in Scandinavia, France, and Australia, but nonexistent in many places where they can be found. In North America crayfish used to be a delicacy exclusive to Louisiana (where they are called "crawfish"), but appreciation of it has for some time been spreading.

The European crayfish Astacus fluviatilis was wiped out in many European countries early in the twentieth century. A species from North America was introduced to important crayfish regions, notably Sweden, as a replacement. Crayfish have considerable importance in the culture of Scandinavian countries, and there are many rules of procedure involved in a crayfish feast, for example, wearing huge napkins round the neck, sucking at the carapace, etc. This applies generally in countries such as Finland and Sweden, where enthusiasm is at its peak. This enthusiasm is sometimes puzzling to people from other regions, given the small amount of nourishment to be had from one small crayfish and the considerable effort and skill required to extract it. However, there are two kinds of crayfish in Australia, besides the Tasmanian one already mentioned, which are large enough to be eaten with less difficulty: the yabby (not a single species but several in the genus Cherax ) and the marron (another Cherax species), which belongs to western Australia and is the third largest crayfish in the world.

To avoid confusion, it is well to note that the word crayfish is properly applied to the species described above, while the word crawfish is normally used to refer to spiny lobsters.

An Oddball

One of the most delicious crustaceans has an appearance that resembles no other crustacean and does not suggest edibility. Moreover it is immobile and has a limited distribution centred on the Iberian Peninsula, to the cultural identity of which it makes a contribution. This strange creature is the goose-necked barnacle, Mitella cornucopia, best known under its Spanish name, percebe. It looks something like a rubbery, scaly tube with a hoof on the end. To eat it, one must prise off the outer tube, exposing a stalklike protuberance which may be bitten off entire. It is usual to boil the creatures briefly before serving them, but they can be eaten raw. It is in Spain and Portugal that percebes are most appreciated. They are costly, since gathering them from the rocks, at the foot of cliffs, to which they are typically attached, is often difficult and sometimes dangerous. A larger relation, Megabalanus psittacus, is found on the west coast of South America and is eaten with enthusiasm in Chile.

See also Arthropods; Fish; Fishing; Iberian Peninsula; Southeast Asia; United States, subentries on Cajun Cooking and Middle Atlantic States.

BIBLIOGRAPHY

Heron-Allen, Edward. Barnacles in Nature and Myth. London: Oxford University Press, 1928.

Holthuis, L. B. Shrimps and Prawns of the World. Rome: Food and Agriculture Organization, 1980.

Holthuis, L. B. Marine Lobsters of the World. FAO Species Catalogue, vol. 13. Rome: Food and Agriculture Organization, 1991.

Olszewski, Peter. Salute to the Humble Yabby. Melbourne: Angus & Robertson, 1980.

Warner, G. F. The Biology of Crabs. London: Elek Science, 1977.

Warner, William B. Beautiful Swimmers: Watermen, Crabs and the Chesapeake Bay. Boston: Little, Brown, 1983.

Alan Davidson