Biodiversity Ireland have issued an Invasive Species Alert for Chinese mitten crab (Eriocheir sinensis).
One berried female with eggs showing signs of development to Zoea stage, was captured by net on 25th January 2021 in Waterford harbour. Another female was photographed 25th December 2020. Chinese mitten crab has been record twice previously in Waterford harbour, one individual in 2006 and 16 crabs in 2009.
See Invasive Species Alert from Biodiversity Ireland for further details.
The Chinese mitten crab life cycle includes phases spent in the marine, brackish and freshwater environments. Most of its life cycle is spent in rivers as an adult but it must migrate to deep, open saltwater locations to reproduce. In the spring, the eggs hatch into larvae and after about six to seven weeks these metamorphose into juvenile crabs, which then migrate back up the river into freshwater to complete the life cycle.
As Chinese mitten crab burrow into river banks, they leave behind holes about 3 cm in diameter. Dead bodies (carapaces) may also be found washed up but positive identification would require the mittens to be present. There are no other freshwater (river) crabs present in Ireland.
In Ireland please submit your suspected sightings (if possible with a photograph) through this online form https://records.biodiversityireland.ie/record/invasives or the Biodiversity Data capture app.