Nineteen fish species of fifteen genera and three families; Cyprinidae, Poeciliidae and Nemacheilidae are recorded from Gheshlagh river (Geshlagh Reservoir and River), Kurdistan, Iran. Ten species were accounted as endemic to Tigris basin; Squalius cephalus, S. lepidus, Capoeta trutta, C. damascina, Garra rufa, Barbus lacerta, Luciobarbus barbulus, Alburnus mossulensis, Alburnus sp and Oxynoemacheilus sp. The others were non native. Cyprinus carpio, Hypophthalmichthys molitrix, H. nobilis and Ctenopharyngodon idella were transplanted as species for Geshlagh Reservoir fishery enhancements. The other species were Rutilus kutum and Hemiculter leucisculus which both are most likely to be introduced from the Caspian Sea basin, accidentally. Carassius auratus, Pseudorasbora parva and Gambusia holbrooki were also recorded as exotic to this system. Presently, 47.37% of fish fauna in this river system are exotic and this could be a warning or may benefit for this system. The conclusion on this matter will be depending on future detail study.
