Population features and threats to the Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Iranian Dolphins’ Bay Natural Heritage in the Strait of Hormuz, eastern Persian Gulf
Background and aims: although small cetaceans in the Persian Gulf suffer from massive anthropogenic impacts, population biology and conservation status of their communities are unknown in most parts of this semi-enclosed shallow sea. A semi-resident community of Indo-Pacific bottlenose dolphins inhabits the Dolphin’s Bay Natural Heritage, a nationally protected area (~97 Km2) and the only Iranian dolphin-watching tourism site, located in the Strait of Hormuz. This study was undertaken to estimate for the first time size, structure, home range, and threats to this dolphin community. Activities: data were collected during 16 small-boat surveys (~ 27 hours) in December 2017 and February 2018. The photo-identification technique was used to estimate the community size. Findings and conservation implications: the size of the bottlenose dolphin community was estimated at 126 individuals. In addition, at least four neonates were observed during February, confirming the bay is a breeding habitat for this community. The group size ranged from eight to 100 individuals, observed in one to five subgroups, a mixture of adults, juveniles and calves. Based on previous observations, dolphins usually migrate to unknown areas seaward during late spring and summer months. Our surveys showed that during their presence, their home-range exceeds the easternmost limit of the bay, which calls for an immediate measure to expand the boundaries of the protected area. Fishing activities (e.g. purse-seines, fish hooks, cage liked traps), which were recorded during 60 % of boat surveys, are the main putative threat for the dolphins. Further, while skippers are not trained for responsible dolphin-watching, tourism boat traffic is another threat for the dolphins. Therefore, the top priority is to cooperate with local communities aiming to promote responsible dolphin-watching, help develop alternative livelihood options for fishers and encourage fishing outside the protected area in order to reduce incidental bycatch and competition for fish resources.