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Based on the morphology and corallites structures, seventeen species of scleractinian corals in seven families were described from the Chabahar Bay, fourteen species of which are being reported for the first time from this bay. The identified species include  Acropora valida Dana, 1846,  Acropora clathrata Brook, 1891 and  Acropora nausta Dana, 1846 belonging to Acroporidae, Favia matthai Vaughan, 1918, Favites complanata Ehrenberg, 1824, Favites flexusa Dana, 1846, Leptastrea purpurea Dana, 1846, Faviafavus Forskal, 1775 and Cyphastrea microphtalma Lamarck, 1816 belonging to Favidae, Acanthastrea hillae Wells, 1955 and Scolymia australis Milne Edwards and Haime, 1849 belonging to Musidae, Pocillopora damicornis Linnaeus, 1758 belonging to Pocilloporidae, Porites solida Forskal, 1775 and  Porites compressa Dana, 1846 belonging to Poritidae, Coscinaraea wellis Veron & Pichon, 1980 and Pseudosiderastrea tayami Yab and Sugiyama, 1935 belonging to Siderastreidae and Turbinaria peltata Esper, 1794 belonging to Dendrophylliidae, were identified.

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Settlement of benthic community depends on environmental conditions and interspecific reactions. The effect of substrates on the surface cover by the soft coral, Zoanthus sansibaricus, and the brown algae, Iyengaria stellata and their computational condition, was compared in the Hormuz Island by estimating of coverage area in 40 quadrates (50×50 cm). Z. sansibaricus is a dominant soft coarl (Zoanthid) species in Hormuz island coasts in the other side I. stellata considered as dominant macroalgea, most of year in area. Significant negative correlation (p<0.01; r = -0.607) revealed competition between two species in settlement on the two substrates. Soft coral with 61.7% coverage was dominant vs. 16.8% for brown algae on muddy-Rubble substrate, but on sandy-Rubble substrate, the brown algae was dominant with 37.8% coverage vs. 19.5% for the soft coral. It seems that better compitiunal conditions in settlement on unconsolidated substrate have some advantages for Z. sansibaricus on Muddy-rubble substrate.

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Aims: Monitoring of the fish biomass is one of the basic principal of fisheries management, but ornamental and reef fish stocks, because of difficulty of estimating their abundance, have been less studied than others. The aim of this study was to estimate the standing biomass of ornamental and reef fishes in Larak Island, in the Strait of Hormuz.
Materials &Methods: Standing biomass of the fish species was assessed seasonally using Underwater Visual Census Method (UVCm) in coral reefs and  mesophotic coral reefs in Larak Island throughout 2018 and 2019. Two popular methods in UVCm (belt transect and stationary point) were used based on topography of sea bottom. The confidence interval of estimated standing biomass is calculated using bootstrapping method.
Findings: The standing biomass of ornamental and reef fishes is estimated as 2522.18, 5222.17 and 1325.15(Kg.) in Site 1, Site 2 and Site 3, that are located in 3-15meters depth. The standing biomass at Site 4, was estimated as 884.13kg. The minimum were observed in summer, also the result showed  that the standing biomass in summer was significantly lower than other seasons (P <0.05). In addition, the temporal diagnostic test showed that population structure of fish in the spring, autumn, and winter seasons was similar but significantly different from the population structure in summer.
Conclusion: The less of standing biomass in summer season can be affected  by seasonal migrations of fish in tropical and subtropical waters to deeper waters, in order to trade of the stresses caused by temperature fluctuations.
 

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The Persian Gulf has a different environment for corals compared to other parts of the world. 17 coral islands and some coastal areas in the northern part of the Persian Gulf as well as Chabahar Bay in the Oman Sea are the most important coral regions of Iran. The inaccessibility of coral islands and the dispersion of research have led to inaccurate information on the number of coral reef species identified. In this research, by field study of some coral regions such as Shidvar, Farsi, Kharg, Khargo, Hindurabi and Nayband, as well as collecting studies conducted by other researchers in other coral regions, thorough information about the diversity of coral species identified in the Persian Gulf have been presented. According to studies, the number of species of coral reefs identified in the Persian Gulf waters is 96 species, which by calculating 6 species of coral reefs that are reported only from Chabahar Bay, brings the number of species identified in Iranian waters to 102 species. The identified species are from 13 families and 40 genera, among which, Merulinidae and Acroporidae each with 29 and 23 species, respectively, have the highest diversity in terms of number of species. After these two families, Poritidae with 11 species has more diversity than other families. Among the studied islands, Larak Island has the highest number of species.

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Estimation of coral fishes biomass is needed as a basic benchmark for assessing the ecological status and fishing potential of coral reefs. Different methods are used to sampling the biomass of these communities, that direct observation is one of the preferred methods with respect to the non-destructive advantage. The purpose of investigation was to estimation standing biomass of coral fishes by Underwater Visual Census method (UVCm) in Abu-Musa Island seasonally from October 2019 to September 2020. also confidence interval was calculated of these estimations from the bootstrapping test (95%). Standing biomass of Coral fish and their confidence interval (95%) by bootstrapping simulation (n=479) were determinated 2923.6 kg., 4576.2 kg, and 1645.4 kg for the stations one, two and three respectively. The difference in the biomass standing of coral fish in three station could be related to the lack of differences in the amount of developed reefs, coral communities and significant differences in habitat availability.  Also, the standing biomass of coral fishes in the Abu-Musa Island are limited, that can be attributed to their low habitat, shortage of carrying capacity and the short life of the Persian Gulf basin, and stress that occurs in the ecosystem, especially bleaching events, that need more study in the future.

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Investigating the trend of temperature changes occurring in the Persian Gulf can be used to determine the pattern of climate change in the region and to study the impact of these changes on aquatic habitats in the Persian Gulf waters.  This study was carried out to investigate the changes in sea surface temperature and sea surface temperature anomaly in Kharg and Hendourabi islands by using Environmental Research Division's Data Access Program (ERDDAP) of National Oceanic and Atmospheric Administration (NOAA) and  daily sea surface temperature and sea surface temperature anomaly  were investigated over a 35-year period.The results showed that the average annual surface temperature increased by about 1 °C over 35 years in Kharg and Hendourabi Islands and the average annual sea surface temperature anomaly in these islands were increased by 2 °C. The slope of this increasing trend on Kharg Island was more severe than Hendourabi Island. The most significant bleaching event in the Persian Gulf occurred in 2016-2017, with the highest increase in temperature in 2017. As water temperatures continue to increase in the coming years, the living conditions of the Persian Gulf corals are likely to deteriorate, and only some resistant species can survive in the Gulf.