Abstract
The temporal and spatial patterns of species composition and the abundance of fish in the mangrove estuaries of the Gesashi River on Okinawa Island, the Shimajiri River on Miyako Island, the Nagura River on Ishigaki Island and the Urauchi River on Iriomote Island were studied during August, from 2000 to 2002. Fish samples were collected by cast nets, hand nets, and angling. In total, 5,747 individuals representing 13 orders, 47 families, 104 genera and 155 species were recorded from four mangrove estuaries. The number of species was found to increase from north to south. In terms of individual numbers, several species represented dominant key species, which comprised over 50% of the total number of individuals collected in each estuary. In terms of the number of species per family, the most dominant family was the Gobiidae in each river and accounted for 25.5% of the total number of species that appeared in the Gesashi River, 30.2% in the Shimajiri River, 40.7% in the Nagura River, and 38.1% in the Urauchi River. The diversity of fish species found in the Okinawan mangrove estuaries was considered to be similar to or greater than those in other tropical regions.
