Observations of mobile macro-epifauna on pumice rafts generated by Fukutoku-Oka-no-Ba volcano in Oku Port, Okinawa Prefecture

Abstract

We report the presence of mobile macro-epifauna on rafts of pumice generated by the Fukutoku-Oka-no-Ba volcano in 2021 in Oku Port, at the northern end of Okinawa Island. Most of the water surface in the harbor was covered by a thick pumice raft at the time of our observations. Grapsus crabs were the dominant species on the surface of the raft, and many crabs were visible near the quay. No crab was seen to burrow into the raft. These results show that mobile macro-epifauna can expand their distribution to the surface of a pumice raft. However, the presence of a raft is likely to make it difficult for crabs to move between land and water.