715,000 Chinese mitten crabs netted this year

Summary

The famously invasive species of crab are pulled from Flemish waters, where they eat the riverbeds clean and threaten other species

Second trap in the works

Flanders Environment Agency have netted 715,000 Chinese mitten crabs so far this season, a process that takes place on the Kleine Nete river in Grobbendonk. The invasive species multiplies by the millions every year and eats up everything in its path on river beds if not captured and pulled from the waters.

The crab species (Ericheir sinensis), named for its furry claws, is native to Korea and China but managed to migrate to Europe – probably in commercial vessels – more than 100 years ago. The crabs adapt easily to water conditions, including polluted waters, and multiply rapidly. They are a threat to local crab populations as well as small fish species and freshwater plants, which they hoover up from riverbeds by the millions.

Flanders captures the crabs with a specially developed trap that runs along the width of the Kleine Nete (pictured below). When the crabs try to climb over it, they fall inside a narrow slit and then, looking for a way out, follow a tube that leads to a receptacle. The receptacle lets them in, but not out.


The crabs are then collected by agency workers, who anaesthetise them and deliver them to a local company, where they are ground up and disposed of or used for other purposes, like fish food.

“We are starting work now on another snare in the Kalken canal in Wichelen,” Katrien Smet of Flanders Environment Agency told VRT. “There are a huge number of Chinese mitten crabs that move along that canal.”

The crabs are known to feed in fresh water but then travel towards brackish waters at the mouths of rivers to mate. That’s when they are caught by the snare system. “In fact, Chinese mitten crabs are found in many waters in Flanders, but unfortunately, it’s not possible to build these snares in all of those places.”

Photo top courtesy Manchester Museum; photo above courtesy VRT