Far-reaching blues: Long-distance migration of the invasive Atlantic blue crab

Abstract

Upstream migration of the Atlantic blue crab Callinectes sapidus is well described in its native range, but it is little known in invaded areas. Here, we report several long-distance migration events of the blue crab in the Iberian Peninsula and use a global database to calculate the probability of occurrence of the species in relation to distance to sea. We then exemplify the potential of blue crab impacts on freshwaters by overlapping its probability of occurrence with that of the critically endangered European eel Anguilla anguilla. Finally, we evaluate the extent to which dam barriers can halt the upstream migration of the blue crab. Invasive blue crab has been detected at 108 km from the sea in the Guadalquivir River (the farthest distance reported in the non-native range), at 71 km in the Guadiana River and at 53 km in the Ebro River. The probability of occurrence decreased steeply in the first upstream kilometres, but it is still concerning at a dozen kilometres from the river mouth (50% at 19 km, 25% at 38 km, and 3% at 100 km). The blue crab invasive potential widely overlaps (63%) with the Iberian range of the European eel. The blocking effect of dams on the potential invasion of freshwater systems by the blue crab was limited (13%). Our study highlights the need to study the upstream migration of the blue crab within its non-native range, since it could involve serious impacts in reachable river and stream habitats.