Search: Thames mitten crab
An invasive species of crab which is causing environmental damage to the Thames could be controlled by harvesting them for eating, scientists have said.
The Chinese mitten crab has colonised the Thames and is establishing itself in other rivers around England, where it can burrow into and destroy fragile riverbanks, prey on other species and compete with native animals such as crayfish.
But a report into whether the Thames population of the crab, which is a popular delicacy in south east Asia, is fit for eating concludes that catching them for culinary use could be a commercially viable way of controlling the species.
A two-year pilot fishing programme by the Natural History Museum to investigate how to reduce the population of mitten crabs in the Thames first raised the possibility of harvesting the species for restaurants and specialist food shops.
But the London Port Health Authority (LPHA), which is the food authority for the Thames, needed research into whether the crab was suitable for human consumption.
Scientists from the LPHA, along with experts from the Natural History Museum, the Centre for Environment, Fisheries and Aquaculture Science (Cefas), the Food Standards Agency and the Central Science Laboratory have been assessing any potential health risks.
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Testing of samples of the crabs' white and brown meat revealed that levels of metal and hydrocarbon contaminants were too low to be of concern but organochlorines, including dioxins, were relatively high.
But levels were higher in crabs from the Netherlands, from where most London food businesses source their mitten crabs, according to the researchers.
The experts said it was unlikely anyone would eat enough crabs for it to be a risk to health, especially as portions were small and the mitten crabs were only available for three to four months a year, though the FSA warns against girls and women up to child-bearing age eating too much crab.
Dr Paul Clark, zoologist at the Natural History Museum, said the crab had occupied a niche left vacant by the absence of crayfish and had exploited it. "The mitten crab appears in the Thames in large numbers, and it seems to be gradually dispersing westwards. It's eating everything in sight and the other problem is it burrows into soft banks," he said.
