The Persian Gulf is positioned in the heart of the Middle East as one of the most critical water bodies. Indian Ocean humpback dolphins (Sousa plumbea) are distributed in nearshore waters and are therefore highly vulnerable to a variety of anthropogenic pressures. To our knowledge, there is a little information and data available about habitat use and abundance of this endangered species in Iranian waters. In the present study, baseline data about population size and site fidelity of Indian Ocean humpback dolphins in the Dayer-Nakhiloo Marine National Park in Northern Persian Gulf, Iran, has been explored for the first time. From March 2014 to December 2018, 127 boat-based surveys and 6436 km of survey effort were conducted. Overall, 127 groups of humpback dolphins were observed on 62% of the surveys. Humpback dolphin group size ranged from 1 to 14 individuals (mean 5.8 ± SE 0.3). Abundance estimates were calculated and fitted with open population models. Thirty (95% CI 22–38) humpback dolphins were estimated to inhabit the study area. There was a lack of seasonality in the occurrence of humpback dolphins and strong site fidelity within the Dayer-Nakhiloo Marine National Park. Most of the identified individuals used the study zone regularly (79.5%), while a smaller number were present less often. The results of this study provide important baseline information about humpback dolphin ecology in an area subject to significant anthropogenic pressures which can help to take effective conservation and management measures.

波斯湾位于中东的中心地带，是最重要的水体之一。印度洋座头海豚 ( Sousa plumbea )) 分布在近岸水域，因此极易受到各种人为压力的影响。据我们所知，关于伊朗水域中这种濒危物种的栖息地使用和丰富度的信息和数据很少。在本研究中，首次探索了伊朗北部波斯湾 Dayer-Nakhiloo 海洋国家公园印度洋座头海豚种群规模和地点保真度的基线数据。从 2014 年 3 月到 2018 年 12 月，进行了 127 次船基调查和 6436 公里的调查工作。总体而言，在 62% 的调查中观察到 127 组座头海豚。座头海豚群的规模从 1 到 14 人不等（平均 5.8 ± SE 0.3）。计算丰度估计值并拟合开放人口模型。估计有 30 只（95% CI 22-38）座头海豚栖息在研究区域。Dayer-Nakhiloo 海洋国家公园内座头海豚的出现缺乏季节性和强烈的场地保真度。大多数被确定的人经常使用研究区（79.5%），而少数人不经常出现。这项研究的结果提供了有关座头海豚生态学的重要基线信息，该地区受到重大人为压力的影响，有助于采取有效的保护和管理措施。而较少出现的人数较少。这项研究的结果提供了有关座头海豚生态学的重要基线信息，这些信息可能会受到重大人为压力的影响，有助于采取有效的保护和管理措施。而较少出现的人数较少。这项研究的结果提供了有关座头海豚生态学的重要基线信息，该地区受到重大人为压力的影响，有助于采取有效的保护和管理措施。