This Marine IBA is identified using both tracking data and seaward extensions around breeding colonies. It falls within the Japan Exclusive Economic Zone (EEZ) and the Pacific, Northwest FAO ocean region. The site covers an area of 51254 km2 and borders the coastline. The depth ranges from 0 to 8138 m, with a mean annual wind speed of 2.03 m/s and mean annual sea surface temperature falls between 12.95 and 22.25 °C.
4 species trigger IBA criteria at this Marine IBA. BirdLife analyses of tracking data estimates that 698276-1241379 individuals of Streaked Shearwater (LC) from Japan are present at the site during the Non-breeding (Oct-Dec) life-history stage. 3750000-4166667 individuals of Sooty Shearwater (NT) from New Zealand are present at the site during the Non-breeding (May-Jul) life-history stage. Seaward extensions around breeding colony; Sanganjima islet include key near-colony areas for breeding populations of Streaked Shearwater (LC) and Black-tailed Gull (LC) 20000-40000 individuals.
BirdLife International (2020) Important Bird Areas factsheet: Futagojima islets / Sanganjima islet - Marine. Downloaded from http://www.birdlife.org on 21/02/2020.