Boundaries

The ecoregion comprises the rivers draining the southern Zagros Mountains to the Straits of Hormuz in southern Iran. It also includes some coastal islands, the largest of which is Qeshm (Jazireh-ye). It is bounded by the Upper Tigris & Euphrates ecoregion [442] to the west, Kavir & Lut Deserts ecoregion [448] to the north, and Baluchistan [701] ecoregion to the east.

Topography

In the west the landscape comprises a series of linear ridges that parallel the coast, with intermittent valleys that drain eastwards. In the north and eastern part of the ecoregion the rivers flow south from the southern Zagros Mountains through wide and open valleys. There is a low-lying coastal plain, the large island of Qeshm, and several smaller islands in the Strait of Hormuz.

Freshwater habitats

All of the rivers in this ecoregion are relatively small and shallow. Many are saline from draining or from salt domes, and sections dry up in summer and reconnect with winter rainfall. There is little to no riparian vegetation. Since rainfall and cloud cover is light, insolation is an important factor, with stream temperatures exceeding 33 °C in winter. Qanats are another important feature. There is a hot spring (41°C) at Genu just north of Bandar-e Abbas in the Geno Protected Area (Biosphere Reserve) (Zehzad et al. 1997).

The principal river is the Kul, with its tributary the Shur (= salt) River. The upper reaches of the Shur lie west of Darab where mountains exceed 3000 m. The headwaters of the Shur approach those of the eastern tributaries of the Mand River in the Tigris-Euphrates basin. The Rasul River is a tributary of the Kul, whereas the Mehran River drains directly into the sea. The Mehran delta lies in the Hara Protected Area (Biosphere Reserve) described by Zehzad et al. (1998). A number of streams cross the plain east of Bandar-e Abbas, draining the Kuh-e Furgun at 3279 m and associated ranges. Although many streams are salty, a freshwater oasis is found at Sar Khun.

Several islands in the Persian (= Arabian) Gulf are included as part of this basin. The largest island is Qeshm, which lacks rivers although there are some small dams to collect rainwater runoff (A. R. Zeanaie, pers. comm. 1999).

Terrestrial habitats

The terrestrial landscape is semi-desert with rocky ridges and plains, and little vegetation. Salt domes are a particular feather that rise over 1200 m above the surrounding land surface. Consequently, the surface water is often contaminated and stream banks are rimed with salt. There is some surviving forest dominated by Quercus spp. in the mountains.

Description of endemic fishes

The ecoregion contains three endemics. The Iranian cichlid, Iranocichla hormuzensis, is an endemic genus and species with relatives in the Levant and Africa and no other cichlids in intervening waters. There is also the balitorid, Seminemacheilus tongiorgii, and the tooth-carp, Aphanius ginaonis, which is restricted to a hot spring at Genu (27º26’N, 56º20’E). The distinction of the latter from the more widespread A. dispar is disputed by some authors.

Ecological phenomena

The hot spring tooth carp, Aphanius ginaonis, is an important taxon for studying adaptation to unusual environments and the limits of species definitions. Many of the fish species are evidently adapted to saline stream environments with high temperatures.

Justification for delineation

This basin represents the southernmost limit of the genus Barbus s.l., contains a mix of taxa from basins to the east and west, is the only basin with a hot spring endemic in southwest Asia, and has an endemic cichlid genus and species remote from other members of this family. Deltas of the Gaz, Hara, Shur, Minab, and Shirin rivers are Ramsar sites.

Level of taxonomic exploration

Good