Accurate descriptions of distribution and habitat are important for effective We examined the distribution patterns and habitat preferences of two related gizzard shads, Nematalosa japonica and N. come, based on specimens, reports and fish market research in the Ryukyu Archipelago. Both species are N. japonica to the north of Okinawa-jima Island, and come in waters off Amami-ohshima Island and the Okinawa Islands, thereby being distributed at Amami-oshima Island and Okinawa-jima Island. Natural between the two species, found only at Okinawa-jima Island indicated that is a natural hybrid zone. Analysis using a random forest method and fish market N. japonica was most affected by tidal flat type tidal flats), the species being dominant in restricted fishing grounds (Nakagusuku and Haneji coastal waters) that include many coastal tidal flats. However, N. come fected by bottom sediment type, the species being dominant in a of fishing grounds (Kin and Nago Bays, and Nanbu-higashi, Nago-higashi, Nakijin Shioya coastal waters). Thus, the distribution pattern of the two species at OkinawaIsland was affected by environmental factors, such as tidal flat type, and area and sediments. Our findings indicated a clear discontinuity in home range between the fort (CPUE) of the two species has highly altered environments. These findings indicated that the diminution of suitable Okinawan populations of both species. Accordingly, the two Nematalosa species are as being of good indicators of the health and conservation of shallow areas, such as tidal flats. Shallow habitats should be conserved to preserve healthy populations of the two species.
