Impacts of Saltwater Intrusion on the Fish Assemblage in the Middle Part of Shatt Al-Arab River, Iraq

In 2018, a serious changes in the salinity of the Shatt Al-Arab river, as salinity intrusion progressed further to upper reaches of the river due to sharply decline in river flow. Therefore, the fish assemblage structure in the middle of the river, from？ Sindbad and Abu Al-Khasibs was assessed during the period from January to December 2018. Fish were sampled by gill nets, cast net and electro-fishing from both sites. Salinity fluctuated from 2.0‰ (January) in both sites to 16.2 and 25.0% during August in both sites, respectively. 35 and 44 fish species were collected from both sites, respectively, these included 18 marine species in first site and 28 marine species in second site. Poecilia latipinna, Tenualosa ilisha and Oreochromis aureus were the dominant species in first site, whereas O. aureus, Carassius auratus and P. latipinna in second site. The index of species richness, diversity and evenness each showed a consistent seasonal pattern in both sites. The highest value of Bray-Curtis similarity index of fish species between both sites was noted during the period of low salinity. Findings indicate that the salinity values and the percentages of marine and occasional species were considerably higher than that documented in the previous studies on this part of the ？river.