Resembling miniature lobsters, freshwater crayfish are small crustaceans dwelling in cool and clean rocky streams, brooks, ponds and lakes. Crayfish are commonly consumed in Sweden and Finland, where special crayfish parties are arranged during their catching season.
Of the hundreds of crayfish species occurring around the world, two are found in England — the native White Clawed Crayfish Austropotamobius pallipes and the imported Signal Crayfish Pacifastacus leniusculus. The signal crayfish is a species of freshwater crayfish found in western North America, where they are more commonly called crawfish. Crawfish are a popular ingredient in Cajun and Creole cuisine, especially in the southern state of Louisiana, U.S.A.
Why is the Signal Crayfish here? In the 1970's British farmers were encouraged to find new ways to make money and Crayfish looked like a good bet. Good bet it was untill the bottom fell out of the Crayfish market in the 1980's. Crayfish ponds fell into disrepair and many Crays escaped into the British Waterways. Once in the rivers the populations grew and spread rapidly.
It is widely thought that Crayfish will travel widely in the search for food. Whereas this is correct if there is no food available, but, in most clean water syetems food is plentiful, if only to get it is highly competitive. Consequently we find the Cray is both a loner, only becoming social at mating times (September through November), and is fiercely territorial. Whereas the Cray would prefer to live under boulders and logs they will dig burrows deep into bankside vegitation. Its probable that Juveniles do most of the travelling re-populating areas of decline.
The body of crayfish consists of the head, the thorax and the abdomen, which includes the edible tail. The body is covered by a protective, hard outer shell. The crayfish have two pairs of antennae and five pairs of legs, of which the first pair are developed into pincer-like claws, used for gathering food, burrowing and fighting.
Crayfish thrive in unpolluted waters, thus acting as monitors of water quality conditions. Their habitat must offer them suitable nooks and holes where they dwell and hide during the day. They do not leave their shelter until the nightfall.
Although being principally vegetarian, crayfish are also omnivores, even cannibals, eating anything from decaying roots and leaves to meat, including crayfish smaller than themselves. Crayfish bred in fish farms are fed with vegetables and fruits.
Crayfish are solitary animals, meeting other crayfish only during mating season. They reach maturity at the age of 4 to 6 years. The mating takes place in September through to October and the young are hatched on the following summer.
The Caviar of Crustaceans
Crayfish are regarded as a great delicacy. In Europe, they are known to been eaten already in the Middle Ages, when they were popular food among monks during fast days. In many monasteries, crayfish were expressly grown for food in fish tanks. Crayfish were also eaten in courts and among the nobility throughout Europe.
The demand for crayfish grew as they became a highly fashionable delicacy in the 19th century France. From there the custom of feasting on crayfish spread to other European countries, reaching also Sweden and Finland, where crayfish stocks were particularly abundant at the time. Large amounts of crayfish were exported from Finland at the turn of the 19th and 20th centuries, about as much as 15 million individuals a year.
Even though the stocks of native crayfish have since declined due to the crayfish plague, the revival and protecting of the stocks and import of signal crayfish stocks have ensured that crayfish can be enjoyed also in the future.
Signal crayfish from North America were imported to English waters in the 1970's. Compared to gray crayfish, signal crayfish reaches maturity twice as quick and produces more eggs and young. It has a harder shell than gray crayfish, and is more difficult to peel. Various blind tasting tests have indicated that there is no significant taste difference between the two species.
Crayfish plague
From the 1860's on, the native stocks of European crayfish have been drastically reduced due to the crayfish plague, a disease native to North America. It first spread to the European waters probably with ballast water released from a North American ship, and again later with the implantations of North American signal crayfish (from the 1960's on).
The plague is caused by a parasitic fungus, Aphanomyces astaci . It does not much harm the signal crayfish, which are often carriers of it, but is lethal to both noble and narrow-fingered crayfish that are not resistant to it. The fungus infects the crayfish by attaching itself on its shell. It starts to grow fungal filaments, penetrating through the shell into the soft tissue below, killing the crayfish within 6 to 10 days.
The fungus is easily spread from one crayfish to another, but also from one lake system to another. This mostly happens if infected crayfish or non-sterilized fishing equipment used in contaminated water are moved to uncontaminated waters. Currently no other preventative measure than maintaining the highest level of sanitation is known to stop the spreading of the fungus.
The crayfish plague is in no way harmful to humans.
