Oman Research Update: Preliminary survey results and update on deep water acoustic deployments
A. Willson, G. Minton, F. Christiansen, S. Cerchio, D. Cholewiak, R. Baldwin, T. Collins, D. MacDonald, M. Sarrouf Willson and S. Al Harthi
Cetacean research has been conducted in Dhofar, the southern region of Oman, since 2000.During this time,efforts have been primarily focused on documenting the distribution, abundance, and ecology of an Endangered population of Arabian Sea humpback whales (ASHWs, Megaptera novaeangliae). The research has revealed the Hallaniyats Bay to be a habitat of importance for reproductive and foraging related behaviours. Following three years of shorter opportunistic surveys between 2018 and 2020, a 2 week-long survey was conducted in March 2021 with the main objectives of recovering and redeploying a moored passive acoustic monitoring unit deployed in March 2020 for the purpose of detecting blue whale song andassessing the body condition of humpback whales using Unmanned Aerial Vehicles (UAVs/drones). The passive acoustic monitoring unit was recovered, and data successfully retrieved, although an equipment malfunction resulted in the recorder stopping after 7 months of successful data collection. Equipment has beensent for repair prior to a planned redeployment in late April 2021. Thirteen consecutive days of small vessel-based survey effort yielded multiple sightings of common dolphins (Delphinus delphistropicalis), Bryde’s whales (Balaenoptera edeni), Risso’s dolphins (Grampus griseus), Indian Ocean humpback dolphins (Sousa plumbea), Indo-Pacific bottlenose dolphins (Tursiops aduncus), and false killer whales (Pseudorca crassidens), as well as a single sighting of dwarf sperm whales (Kogia sima). However, neither humpback whales nor blue whales were detected during the survey, either visually or acoustically during the multiple hydrophone deployments conducted daily for humpback whale song throughout the survey area. Reasons for the absence of ASHWs in the study area is currently unknown,but could be related to warmer water temperatures potentially influencing their prey species and hence distribution.