The paper reports fish bone and shellfish assemblages from Ulong Island in the Rock Islands of Palau, western Micronesia dating from ∼3100 to 500 BP. Use of marine resources in early prehistory appears to have been highly localised with increasing capture of outer-reef/pelagic taxa including shark and tuna after 1000 BP. Local stocks of large Tridacnids were depleted during initial human use of Ulong Island, and there is a size decrease in Scarus sp. remains consistent with pressure on the inshore fishery, especially after establishment of permanent stonework villages in late prehistory. Comparison of archaeological assemblages of fish bone from other Rock Islands dated to after 2000 BP indicate that the captured fish species and major capture methods differ between sites and likely reflect local marine environments at each location. Copyright © 2010 John Wiley & Sons, Ltd.