Analyses of fish community structure changes in three subtropical estuaries from the Iranian coastal waters

In this study, we analyse the fish species diversity and distribution patterns to determine the potential role of environmental variables as drivers of fish community structure and composition. Thus, we investigated the distributional patterns of estuarine fish and their environmental correlates along a broad spatial scale encompassing three subtropical estuaries from the Iranian coastal waters using multivariate techniques. According to their relative densities, the fish fauna was dominated by the following ten species: Leiognathus brevirostris (17.1 %), Valamugil seheli (16.4 %), Ambassis gymnocephalus (10.4 %), Gerres filamentosus (9.3 %), Gerres longirostris (7.4 %), Leiognathus bindus (7.2 %), Thryssa vitrirostris (4.6 %), Sillago sihama (4.1 %), Megalops cyprinoides (3.9 %), and Nematalosa nasus (3.8 %). Leiognathidae and Mugilidae, represented by seven and six species, contributed 26.17 % and 19.11 % of numerical abundance of the total catch. Hierarchical cluster analysis and nMDS showed a clear spatial segregation of stations from different parts of estuaries according to similarities in their species compositions. Canonical correspondence analyses indicated that temperature, dissolved oxygen, pH and salinity were the four main variables influencing the occurrence of fishes within the estuarine systems. Our results support the effectiveness of the mangrove forests on fish communities in subtropical estuaries subjected to multiple environmental changes. Overall, the details of these findings are beneficial to understanding and developing suitable conservation strategies for the restoration and management of fish resources in the Markazi, Khalasi and Gabrik estuaries, as well as the other estuaries of the Iranian coastal waters.