Long-term changes in butterflyfish assemblages as indicators of shifts in high-latitude coral communities: Evidence from Amakusa, Japan

Historical and recent records were examined to assess long-term changes in the occurrence of warm-temperate reef fishes around the Amakusa Shimoshima Island, southwestern Japan, focusing on the butterflyfishes (family Chaetodontidae) over a period of more than half a century. Underwater surveys and photographic records from 2013–2025 revealed an increase in butterflyfishes from six in the 1960s to 26 at present. The recent occurrence of these southern species is most plausibly considered as a sign of their poleward range expansion associated with warming seawater temperatures.