On the beaches and rocky areas of the Cíes Islands archipelago (Galicia), very close to the LIFE INSULAR action areas, a massive arrival of thousands of Henslow's swimming crabs (Polybius henslowii), a swimming crustacean that can be dragged towards the coast by the combined action of currents, tides and winds, is being observed for the third time this year. Although this is a natural phenomenon already known on the Galician coast, its intensity is particularly striking.
This episode is related to environmental and biological factors, such as oceanographic conditions, the persistence of northerly winds and the pelagic behavior of this species, which forms large aggregations in the open sea. Being light and fragile organisms, they can easily accumulate on the coastline when they are displaced by wind and waves.
Despite their unattractive appearance when they appear stranded, the Henslow's swimming crabs have a high ecological importance, as they constitute a fundamental trophic resource for fish and seabirds. Their presence is part of the natural dynamics of coastal ecosystems and recalls the complexity of the ecological relationships that sustain the marine biodiversity of the Atlantic Islands of Galicia Maritime-Terrestrial National Park.
