They are vicious, they are aggressive and they've been loose on the Nile. Amany Abdel-Moneim warns of the crayfish menace Crayfish ( procambarus clarkii ) is in origin a North American shellfish; but, introduced into Nile waters in the 1980s, its stay in the river has extended sufficiently to make it a permanent resident. Mohamed Ali Ziyada, Mansoura University professor of environmental studies, recounts the mishap, "the owner of a fish farm near Al-Qanater imported crayfish from the United States, thinking it was some kind of prawn, but it wasn't long before they ate their way through the mud partitions, destroying all the other tanks. What to do? He decided to get rid of the fish by releasing them into the Nile." Since then crayfish has made some business, despite people's initial reluctance to buy it. "I've been selling it for a year now," Um Abdallah, 38, who peddles freshwater crayfish at the Imbaba fish market, explains. "I eat it too, it's delicious. And at LE2-3 a kilogramme it's cheap enough for everyone." Consumers are increasingly familiar with the species, she says, but equally she has serviced independent researchers eager to study the species. Conducted in collaboration with the University of Texas, Ain Shams University Department of Zoology research has revealed that the burrowing habits of crayfish are damaging irrigation and drainage canals. Ziyada explains that the Egyptian environment -- warm weather in combination with an abundant supply of organic material in Nile waters -- is ideal for the growth of this particular species of crayfish, which is characterised by a particular high fertility rate. Such is the rate, in fact, that fishing enthusiasts like taxi-driver Youssri El-Sheikh are complaining that fish have been markedly less abundant since the introduction of crayfish. More significantly, many fishermen and vendors believe the species to be an insect, dangerous and even poisonous. Sobhi Habib, a fisherman who sells his catch at the Imbaba fish market, is rather enraged at the mention of it: "they are a danger to the fish population of the Nile. They are ugly and destructive. They tear my fishing net, they eat my catch, they ravage all they see. They are very bad, very bad." Slow and with weak eyesight, as Ziyada reveals, crayfish will rarely attack any fish other than those that have already been caught. Besides, he adds, they can play a valuable part in ridding the riverbed of dead snails and other water pollutants: as "a biological snail control agent", they are a cheaper, safer means of controlling bilharzia than environmentally hazardous chemical agents. They can also provide a pollution-free source of protein, perfectly safe since all the poisonous material absorbed by crayfish is stored in the shell, which itself is shed six times a year. Ain Shams University researchers have suggested introducing them as a frozen product, perhaps in the form of cold cuts. Boiled alive for seven to 10 minutes, crayfish shed all potentially unhealthy material they might contain and are ready for consumption.
