Wetlands of the Maharlu Lake basin, southern Iran: ichthyofauna and negative effects of exotic fish farming and wetlands drying

The endorehic Maharlu Lake basin in the valley of Shiraz is located in Fars Province, southern Iran. Maharlu Lake is fed by minor streams and springs around its margin and the Khoshk River. In the present study, based on field observations made from August 2017 to March 2018, we provide brief reviews of some wetland habitats of Maharlu Lake basin, present new fish taxa records from this area, and comment on the conservation status of freshwater fish species with regard to the visited habitats. The freshwater resources of the basin host fourteen fish species and two reptile species, among which Acanthobrama persidis (Leuciscidae), Capoeta saadii (Cyprinidae), Oxynoemacheilus persa, Paraschistura naumanni (Nemacheilidae), and Esmaeilius persicus (Aphaniidae) are endemic Iranian species. During the last decade, several exotic carp species have been introduced for aquaculture, namely Carassius auratus, Ctenopharyngodon idella, Cyprinus carpio, and Hypophthalmichthys molitrix, especially to the freshwater bodies at the northern margin of Lake Maharlu, along with the incidentally introduced species Pseudorasbora parva. Our wetland survey efforts did not yield any records for several locally endemic or native taxa (including Acanthobrama persidis, Capoeta saadii, Carasobarbus luteus, Garra rufa, and Esmaeilius persicus). These results, together with our field observations of habitat dehydration suggest that the native and endemic fauna of the Maharlu Lake basin are presently under threat from both natural and anthropogenic factors including drought and introduction of exotic fish species for aquacultural purposes. As a consequence, if the environmental management of the restricted resources of the basin is not implemented in the near future, the combination of these threatening factors will eventually lead to the local extinction of most, if not all, of the populations of these endemic and native species.