The Sulu Goby, Acentrogobius suluensis, is a small fish common in estuaries of the western Pacific Ocean. Specimens recently collected in Pohnpei, Federated States of Micronesia are characterized by a distinctive black spot on the second dorsal fin not observed in the species original description by Herre (1927). To determine whether or not the difference in pigmentation was an indicator of substantive population differentiation, an examination of morphological and pigmentary variation in populations of Acentrogobius suluensis from the central and southwestern Pacific Ocean was conducted.
This distinctive pigmentation is limited to populations in the Caroline Islands and Fiji. Principal Components Analysis revealed associated morphological and meristic features also contributed to distinction among the populations.