 Alarm is mounting on the Indian Ocean island of Madagascar over an invasion of voracious self-cloning crayfish, which are gobbling their way through rice paddies and threatening endemic crayfish species.The marbled crayfish, or marmorkrebs, is color mottled brown-green with light and dark spots and can grow up to 10 centimeters in length.
It is not clear how or when the shrimp-like crustacean, which is believed to originate in North America, came to this vast island, which lies 400 kilometers off the coast of Mozambique.
Experts believe it arrived via Europe, where German scientists already warned in 2003 about the proliferation of the crayfish as aquarium fish.
Professor Olga Ramilijaona, a biologist at the capital’s Universite d’Antananarivo, said the first specimens were discovered in a rice paddy near the capital in 2003.
But the first “invasion” of the Procambarus species came only four years later during the 2007 summer rainy season, when the crayfish, which are sold to impoverished locals as a cheap source of protein, began cropping up for sale on markets.
Today they are found in rice paddies, rivers, lakes and swamps in eight of the country’s 22 regions, mainly in the central high plains, where Antananarivo, the capital, is situated.
“Our seven indigenous crayfish species are directly threatened by these voracious non-endemic species,” Professor Noromalala Raminosoa, also of the capital’s university, told a press conference last week.
Raminsoa said all types of Procambarus are carriers of the crayfish disease, which nearly wiped out European crayfish in former times.
“If nothing is done to stop them these crayfish will become a national threat,” she warned.
Apart from the threat to biodiversity, the crayfish are also devouring young rice plants and attacking small fish bred in rice paddies.
Madagascar’s rice farmers use their paddies as mini-fish farms to supplement their diet — and their income — with small carp and tilapia.
Local daily Midi Madagasikara quoted a farmer from a small village on the outskirts of Antananarivo as saying his catch of tilapia had fallen by about 75 per cent since the crayfish appeared.
The crayfish “will eat any plant matter, including rice. In fact, they’ll eat any biological matter,” the biologists warned.
They also reproduce at an explosive rate, producing up to 400 eggs in 40 days during the warm rainy season.
In 2003, German scientists proved that the marmorkrebs could clone itself. Although the crayfish also reproduced sexually, females were able to lay eggs which hatched without being fertilized.
Known as parthenogenisis, this type of unisex reproduction is effectively a form of natural cloning.
Biologists here fear that if the crayfish continue to gain new ground the impact on the environment of this ecologically sensitive island, which is home to tens of thousands of plants and animals found nowhere else, could be disastrous.
Working with Conservation International, the university has launched a campaign across areas within a 200-kilometer radius of the capital. Using pictorial placards, they warn people against the dangers of the pest, known locally as orana vahiny.
“We get diarrhea after eating them,” one farmer said. “Even the pigs won’t eat them.”
Rice farmers have also grouped together and have began fishing out and burning the crayfish en masse.
Meanwhile, at bush taxi ranks on roads leading out of the capital, volunteers are checking passengers’ baggage to ensure that plateau dwellers are not carrying the crayfish to give as presents to relatives in other regions. |
