| Ōmura Bay | |
| Location: | Nagasaki Prefecture |
| Coords: | 32.95°N 129.875°W |
| Pushpin Map: | Japan Nagasaki Prefecture |
| Oceans: | East China Sea |
| Countries: | Japan |
| Length: | 26km (16miles) |
| Width: | 11km (07miles) |
| Area: | 320km2 |
| Depth: | 15m (49feet) |
| Max-Depth: | 55m (180feet) |
| Shore: | 360km (220miles) |
| Cities: | Nagasaki |
is a bay located in the center of Nagasaki Prefecture, Japan in the East China Sea.
The bay measures about 26km (16miles) north-to-south and 11km (07miles) east-to-west. The length of the shoreline is about 360km (220miles) and the surface area is about 320km2. This corresponds with about 8% of the total area of the prefecture. Compared to its size, the bay is relatively shallow with an average depth of 15m (49feet) and maximum 55m (180feet) depth.[1]
The bay is surrounded by land in all directions, thus it appears as an inland sea on maps. The only two connections to the East China Sea are in the north-west: the with a minimum width of 200m (700feet) and – more eastward – the with a width of 10to. However, these two straits do not directly lead to the open sea, but to the .[2] In between the Hario and Haiki Straits lies Hario Island. West of the Ōmura Bay lies the, and to the south is the foot of . On the eastern shore of the bay is the, on which the city of Ōmura is located. Opposite Ōmura city lies the largest island of the bay: Mishima (箕島), where Nagasaki Airport is located. For this purpose, the island first had to be flattened and reshaped.
Along the bay shore lie the following towns, clockwise from the north: Sasebo, Kawatana, Higashisonogi, Ōmura, Isahaya, Nagayo, Togitsu, Nagasaki and Saikai.
Because of the geography of the bay there is only a small exchange of water from the bay with the sea. Consequently, the marine life in the bay is different from that in the nearby sea. The bay houses a rare species of finless porpoise, which does not leave the bay during its lifetime. Indo-Pacific bottlenose dolphins and common dolphins may migrate into the basin on unclear regularities. [3] Another special inhabitant – sometimes characterised as a living fossil – is the horseshoe crab species Tachypleus tridentatus. Despite being nearly separated from the sea, and the large cities along its shore, the bay is full of fish. About 60 species of marine animals are fished.