A Study on the status of invasive tilapia species (Coptodon zillii Gervais, 1848 and Oreochromis aureus Steindachner, 1864) in aquatic ecosystems of Khuzestan Province, Iran

Invasive fishes are a major threat to biodiversity of aquatic ecosystems. Tilapia species are invasive due to their reproductive, diet and behavioural characteristics and high resistance to environmental conditions, pollution and diseases. So far, two exotic species Coptodon zillii and Oreochromis aureus, as well as a native species Iranocichla hormuzensis of these species, have been reported from Iran. In recent years, exotic tilapia species have invaded Iran and its neighbouring countries inland waters and have had significant ecological and economic impacts. The aim of this study was to conduct a preliminary survey on the status of exotic tilapia species in Khuzestan Province, Iran. The present study was carried out from November 2014 to September 2015 to determine the abundance of tilapia species (C. zillii and O. aureus) in the Shadegan Wetland and some local fish markets in Khuzestan Province. In addition, we the evaluated presence or absence of the species in some cyprinid fish farms in the province. The results showed that the catchment and supply of C. zillii is high and the species is one of the dominant fish in Shadegan Wetland. In this study, although O. aureus was not caught from Shadegan Wetland, observations showed that it has dispersed to other areas, especially in rivers, and its abundance is being increased. The tilapia species especially C. zillii are pests in some fish farms and a reduction of fish production has been noted. The presence of the species in some fish hatcheries has increased the possibility of their transfer to other regions. At the moment, it seems that the best course of action to take action against tilapia is to prevent them from entering other water bodies (especially through aquaculture). The continuous studies to determine various aspects of the introduction, potential range prediction, and regular monitoring should also be also considered. Overall, a compilation method and also ecologically sustainable water management, reduction of water contaminants and decrease of fishing pressure on native species should be adopted for controlling and reducing of these species.