Contents lists available at ScienceDirect Ecological Indicators journal homepage: www.elsevier.com/locate/ecolind Original Articles Population estimate and distribution pattern of Indian Ocean humpback dolphin (Sousa plumbea) in an industrialised bay, northwestern Persian Gulf Mahmoud-Reza Hemami a, ⁎ , Mohsen Ahmadi a , Mohammad Sadegh-Saba b , Seyed Masoud Hosseini Moosavi c a Department of Natural Resources, Isfahan University of Technology, Isfahan, Iran b Marine Environment Bureau, Khuzestan Provincial Office of the Department of Environment, Ahvaz, Iran c No 27, Zolfaghar-8 Street, Phase 2, Mellat District, Ahvaz 6164864938, Iran ARTICLE INFO Keywords: Anthropogenic pressure Cetacean Distribution modelling Abundance estimation Marine transect GAM ABSTRACT Monitoring and assessing marine biodiversity relies upon adequate and accurate knowledge of population and distribution patterns of ecologically important species. Cetaceans are recognised both as functionally important and as flagship species and have been the target of monitoring and conservation programs. The habitat specialist Indian Ocean humpback dolphin (Sousa plumbea) is the second most common cetacean in the Persian Gulf. Mousa Bay in the northwestern Persian Gulf is an important, but highly industrialised habitat for this species. We developed a systematic and comprehensive distance sampling survey carried out from 2014 to 2016 to estimate abundance and population density of humpback dolphin in this bay. To evaluate distribution pattern of the species, eight environmental variables were measured and employed in a zero-inflated generalised additive model (ZINB GAM). With an estimated abundance of 92 animals (64–131, 95% CI) and density of 0.123 animal/ km 2 (0.086–0.176, 95% CI), our results revealed Mousa Bay as one of the largest population of humpback dolphin in northern latitudes of its global range. Based on ZINB GAM findings, distance to coastlines, depth, EC, and chlorophyll a concentration significantly influence the distribution of the species. Our results highlighted that physiographic parameters and resource availability are the most important motivators of the species dis- tribution in shallow nearshore waters. Biotic (e.g. water quality) factors due to strongly being affected by the variability of time and space ranked after physiographic variables. The high tendency of humpback dolphins to enter in highly developed foreshore of Mousa Bay raise the need for conservation-oriented studies to inform conservation planning. This study provides a basis for monitoring humpback dolphin and assessing ecosystem health of northern Persian Gulf. 1. Introduction Despite the importance of ocean-marine ecosystems, the quality of these natural habitats are rapidly declining particularly due to habitat destruction, over-exploitation, introduction of alien species, water pollution and climatic fluctuations (Pompa et al., 2011; Worm et al., 2006). Additionally, close to 60% of the world’s human population is settled at a range of 100 km from shorelines (Pompa et al., 2011). Anthropogenic disturbances in these areas have led to the fact that of the 89 cetacean species, 22% are assigned to threatened (i.e. CR, EN, VU) or near threatened (NT) categories and the conservation status of 50% of them is data deficient (DD) due to the insufficient data of their population trend and geographic distribution (IUCN, 2017). Conse- quently, planning monitoring programs is indispensable for filling conservation gaps and developing management strategies for marine mammals. Nevertheless, despite successful conservation activities and improved population status of some of the marine mammals in recent decades (e.g. whales), those occurring in coastal areas or inland waters (mainly dolphins and porpoises), have constantly been facing threats from human activities (Lotze et al., 2011; Pompa et al., 2011). Ships and boats traffic, habitat destruction, and entanglement in fishing gears are among the most serious threats to marine mammals in these areas (Komoroske and Lewison, 2015). Cetaceans are recognised as functionally important species by the EU Marine Strategy Framework Directive (Azzellino et al., 2014). They are also considered as flagship (Hoyt, 2012), keystone (Bănaru et al., 2013), and umbrella (di Sciara and Agardy, 2016) species and hence are the target of conservation efforts. The Persian Gulf is a relatively small, shallow and semi-enclosed marginal sea of the Indian Ocean bordered by Iran and the Arabian https://doi.org/10.1016/j.ecolind.2018.02.031 Received 21 November 2017; Received in revised form 13 February 2018; Accepted 14 February 2018 ⁎ Corresponding author at: Department of Natural Resources, Isfahan University of Technology, 8415683111, Isfahan, Iran. E-mail address: mrhemami@cc.iut.ac.ir (M.-R. Hemami). Ecological Indicators 89 (2018) 631–638 1470-160X/ © 2018 Published by Elsevier Ltd. T