Fish Species Assemblages in Two Riverine Systems of Mujib Basin in Jordan and the Effects of Impoundment

Mujib and Haidan rivers were sampled in July 2011 to identify fish populations in the riverine system, and to investigate the impact caused by the existence of two dams. Fishes were sampled by electofishing gear through 14 sampling points distributed along the two rivers. The Mujib Dam lake was sampled by gillnets. A total of 2,854 fish specimen were caught during the study of which most consisted of native species but included small numbers of invasive species. The native Capoeta damascina and Oxynoemacheilus insignis were found in both rivers but Garra rufa was only recorded below their confluence to the west. Four invasive species were recorded. The cichlids Oreochromis aureus and Tilapia zillii were sampled along Mujib River, and the African Catfish Clarias gariepinus and the Common Carp Cyprinus carpio were observed only in the lake of Mujib Dam but were not sampled. The construction of the two dams has led to significant changes in the habitats, water flow, and hydrology of the two rivers both upstream and downstream, and enhanced the colonisation of invasive species. There is, therefore, an urgent need to review the management of the system across all stakeholders and to continue monitoring on a regular basis.