The most northerly record of feral Pacific oyster Crassostrea gigas (Thunberg, 1793) in the British Isles

The Pacific oyster Crassostrea gigas (Thunberg, 1793) is an invasive non-native species to Europe, introduced as an aquaculture alternative in 1890. In recent years, C. gigas have expanded their range past 60 degrees N on the east side of the North Sea along the Norwegian coast, consistent with range-expansion predictions. However, the northwest North Sea around the Scottish coast has not shown an equivalent expansion. Here we report collection of two C. gigas specimens north of 60 degrees N in Shetland, corresponding to an increase in the species northwest range of 471 km. These finds have implications for local shellfish aquaculture industries and in the conservation of priority marine habitats that are located in the near vicinity. The findings suggest that the species can spawn and survive at much lower temperatures than those used in current models.