North Sea Shrimp
|North Sea Shrimp|
North Sea Shrimp
|( Linnaeus , 1758)|
The North Sea shrimp ( Crangon crangon ), also sand or beach shrimp , garnet , leek , knat , gray crab , in the plural leek or North Sea crab , in the kitchen language generically called crab , is a small species from the genus Crangon within the family of the Crangonidae . Due to its elongated shape, filigree legs, small scissors and long antennae, it is counted among the shrimp .
When fully grown, North Sea shrimp can reach a length of up to 9.5 centimeters, males stay smaller. They have long antennae and, like most decapod crabs , the first pair of limbs is shaped like scissors. The scissors consist of a small end member that is folded like a pocket knife against a massive base member, a so-called subchela .
The slender body of the North Sea shrimp has an almost round cross-section, its color is grayish-brown. In front are the stalk eyes, the two-branched first antennae (antennae) and the long second antennae with two scaly appendages, the scaphocerites. Among them are five pairs of striding legs . The strong subchelae of the first pair of legs prey on the feeding animals. The second pair of legs with small scissors specializes in cleaning the body and the egg clutch. The articulated and muscular rear body has five pairs of feathered swimming legs and a tail fan formed by the uropods and telson . On the first pair of swimming legs, females have a rabbit-ear-like appendix. Males have a clip-like appendix (appendix masculina) on the second pair of swimming legs. The tail fan is used to quickly escape from enemies by jerking it in, the massive muscle developed for this purpose forms the commercially used "crab meat".
Nourishing animals or pieces of it separated with the mouth limbs get through the mouth and throat into the chewing stomach, then into the ramified midgut complex and finally into the rectum. The remains leave the anus. The green antenna gland with a kidney-like function helps to adapt to differences in salinity . The gills supply oxygen to the body through an open blood circuit powered by the heart. Statocysts at the base of the 1st antennae signal the position when swimming up and down in the open water. A ganglia system controls all movements and sensory functions. The moulting process is hormonally influenced.
The distribution area of the North Sea shrimp extends from the White Sea to the Atlantic coast of Morocco . It is the most widespread type of shrimp on the sandy and muddy coasts of the Eastern Atlantic and the only marine shrimp of fishing importance for Germany.
Individual specimens have been found near Reykjavík since 2003, and later larger numbers . It is believed that the transport took place in the ballast water of ships and that ocean warming now enables a population.
North Sea shrimp live predominantly in the area of river mouths, they get along well with the strongly changing salt content here. The reduced salt content even protects the animals against many marine fish species, and rivers also provide large amounts of nutrients. There is evidence that North Sea prawns have benefited from inadvertent fertilization of the sea with washed-in fertilizers (especially phosphate ). Before the winter cold, they withdraw into deeper water.
Reproduction takes place predominantly at night at the age of one year from April to June and from October / November to March. In the Mediterranean and the Baltic Sea there is only one annual reproductive period, this is in the Mediterranean in winter, in the Baltic Sea in summer. On some sections of the Atlantic coast, three breeding seasons are given, which overlap widely, so that egg-bearing females can be observed all year round. Crab fishermen mostly have female shrimp in their catch. Male shrimp, which are smaller and slimmer at the same age, only rarely make it into the “table crab” sort. This is beneficial for reproduction because shrimp ready for spawning can only be mated shortly after molting. Sexual maturity occurs around a body size of 35 to 40 mm; it is difficult to determine, and in the males there is absolutely no outward sign of it. Fights between rival males for a female have not yet been observed. The males probably find the female through scents, turn them on their backs and place their spermatophores in the female genital pores. The female then fends off further attempts at mating.
One to two days later, the fertilized eggs emerge. The female attaches these to specially grown bristles on the underside of the abdomen. In the course of a year, a shrimp produces 3 to 6 eggs (a total of approx. 10,000 to 20,000 eggs). The larvae hatch after one month in summer and after three months in winter. The first six larval stages initially live free-swimming in the deeper water, but finally migrate into the shallow water of tidal mudflats and sea marshes, where they change to the bottom-living way of life. They are then about 5 millimeters long. The animals eat in the tidal area and are driven back into the tidal creeks with the ebb stream, where they wait for the next tide. After about 25 moltings, sexually mature North Sea shrimp develop from it.
For a long time it has been controversial within science whether North Sea shrimp regularly switch from male to female when they reach a certain height ("protandric hermaphrodites"). Corresponding ratios are widespread in cancer types. According to more recent experiments, such sex reassignment seems to occur, but rarely and as an exception.
The larger animals prefer to stay in deeper water. The offspring of the North Sea shrimp use the Wadden Sea only in the warm season to protect themselves from predators. In summer, both young and larger shrimps sometimes migrate far into the brackish water of the estuaries. With the flood they come on the watts, with the low tide they gather in tidal creeks . In freezing weather, they leave the shallow water, which then cools down considerably.
They usually bury themselves flat in the sand to shelter from birds , fish, and young seals . Pigment cells enable the shrimp to match the color of its crustacean shell to the mud flats. North Sea prawns only become active for eating when it gets dark, they are ambush hunters who do not actively hunt prey. In terms of nutrition, they are opportunists who select prey according to frequency and do not disdain even small conspecifics. Main prey animals are benthic crustaceans ( amphipods , Mysiden, copepods ), worms ( polychaete ), but also young fish. Eating on the siphons of buried mussels protruding from the sand is common. Due to their frequency, they are key ecological species in their habitat with a high impact on their prey.
Due to their frequency, North Sea shrimp are also of great importance for hunters (predators). In a study in England the density of the shrimp turned out to be surprisingly constant despite a more than tenfold fluctuation in the young animal production, the feeding pressure of fish could be responsible for this, for all shrimp, which at low tide in the narrow remaining water areas none find good hiding places, easy prey. The main enemy of the shrimp was whiting . Shrimp are also important as food for numerous seabird species.
Catch and processing
On the Belgian coast, North Sea shrimp are still caught by fishermen on horseback for tourist purposes . On the flat North Sea beaches of the Belgian coast, cold-blooded animals pull the nets behind them. The catch is immediately cooked and sold on the beach, for example at the crab festival in Oostduinkerke / Flanders.
Crab trawlers have been fishing with a tree trawler since the end of the 19th century . Here, one is bottom trawl towed over the seabed. The catch in the cold months (around the end of November to February) is less or entirely because the North Sea prawns then withdraw into the deeper waters.
The volume of catches in the North Sea in 2005 was around 38,000 tons, in 2011 it was 33,400 tons. This makes the shrimp fishery third among the North Sea fisheries.
Bycatch and cooking
After sorting out the bycatch ( Gammel ), which is possible thrown alive overboard, the perishable brown shrimp are boiled already on board with seawater. They then look pink to red-brown and have curved towards the underside of the body.
Sorting and preserving
On land, the North Sea prawns are sorted by size with the so-called crab sorting machine. A mixture of table salt, benzoic acid and citric acid is also applied to the North Sea shrimp for preservation. A small part of the catch is sold unpeeled directly from the cutter or near the coast.
Before consumption, the cooked North Sea prawns have to be peeled during the so-called crab peeling. For every three kilograms of meat, about one kilogram of meat remains after peeling. 100 g meat contains approx. 369 kJ (= 87 kcal ), 18.6 g protein, 1.44 g fat, 130 µg iodine. The head and back of the animal are each held between two fingers, the shell is bent in the middle and pulled off on both sides with a twisting motion.
Until the 1960s, crab peeling in Germany was largely done at home . Today prohibit EU rules of hygiene reasons, the shelling in their homes for sale. In the context of globalization, this work process has been relocated to Morocco , Poland and Belarus .
Crab peeling machine
Several inventors have registered patents since the 1980s , and some functioning machines are in operation, for example in Spieka-Neufeld and in the Northwest Peeling Center in cooperation with the Butjadinger fishing cooperative. However, the yield of shrimp meat obtained from machine peeling is apparently lower and the process is still significantly more expensive overall than manual processing abroad. However, the possible reduction in transport times and the resulting significantly lower use of preservatives are advantageous.
Crab fishermen on horseback on the North Sea coast (1941)
Shrimp cutter off the German North Sea coast
Use in the kitchen
So-called table crabs , which have a certain minimum size, are marketed as food and are considered a delicacy. North Sea shrimp are particularly popular in Belgium, Northern Germany and England , and they are also often on the menu in other North Sea countries such as France , the Netherlands and Denmark . They are largely cooked on board after they have been caught and are only available to a limited extent as unpeeled table crabs on the coast or from well-stocked fishmongers . The majority is, after mostly long transport to and from the place of “pulping”, marketed as peeled crab meat loose or packaged via the fish or grocery store.
In Germany they are considered a specialty of Northern Germany and are generally used and especially in the kitchen language as North Sea crabs , usually short as crabs and also as leek ( North Friesland ) or garnet ( East Friesland ). The nutty-tasting North Sea crab meat is traditionally used in a number of dishes and dishes in North German cuisine .
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