Native white-clawed crayfish in Britain and Ireland are critically endangered from crayfish plague spread by invasive North American signal crayfish.
Crayfish plague causes rapid mortality in white-clawed crayfish populations, with individuals showing neurological symptoms before death. Signal crayfish, while carrying the plague asymptomatically, cause habitat destruction through burrowing that undermines riverbanks and increases sedimentation, harming a wide range of aquatic species. The sentience of crayfish is increasingly recognised, with research showing they display pain behaviours and stress responses comparable to other arthropods.