The Atlantic blue crab (Callinectes sapidus) has rapidly invaded coastal environments in the western Mediterranean,
but there is no consistent assessment of its impacts yet. We use interviews and long-term data series in
the Ebro Delta (NE Spain) to: i) characterise the evolution of the blue crab invasion; and ii) identify its impacts.
The blue crab was first recorded in 2012, but its expansion started around 2016, with an exponential increase in
abundance between 2017 and 2018. Aquatic communities have tended to be dominated by the blue crab,
coinciding with the steep and consistent declines of several species, including threatened and commercially
exploited ones. Blue crab impacts seem to be exerted even at low abundances, arguably hindering the recovery of
declining species. The blue crab is becoming a keystone species in invaded systems and efforts should be made to
understand its many-folds impacts in order to prevent or mitigate them.