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SC/69A/HIM/07
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Resource ID
20011
Access
Open
Document Number
SC/69A/HIM/07
Full Title
Ship strike risk assessment and mitigation solutions for Arabian Sea humpback whales
Author
Andrew Willson, Brendan Godley, Stephen Pikesley, Gianna Minton, Muhammad Moazzam, Suaad Al Harthi, Maia Sarrouf Willson, Aida Al Jabri, Robert Baldwin, Tim Collins, Matthew Witt
Authors Summary
Willson presented the results of a commercial shipping ship strike risk assessment and associated mitigation measures for Arabian Sea humpback whales (ASHW). The work was motivated by concern for the overlapping of increasing shipping trade (approximately 5% per year, 2009-2018) within the known habitat of this Endangered population. The presented methodology used satellite tracking data from implant tags deployed between 2014 and 2017 to develop an ensemble ecological niche model across their suspected range in the North West Indian Ocean. Ecological niche model rasters were combined with satellite sourced shipping tracking data (Automatic Identification System) to produce a ship strike risk assessment raster across the same range. Model results showed the most suitable ASHW habitat to be located around the periphery of the Arabian Sea, particularly along the continental shelf areas of Oman and Pakistan. Shipping traffic running between regional nodes and ports was also concentrated around the periphery of the Arabian Sea with the highest areas of risk detected off the Arabian Sea coast of Oman, Sea of Oman in the approaches to the Straits of Hormuz and off the south west coast of India in the Laccadives Sea. The ship strike map was used to test mitigation scenarios in a selected area off the Arabian Sea coast of Oman. Simulations routing vessels 40 nmi further offshore from the main route currently used by vessels was found to reduce ship trike risk by as much as 88%. Re-routing of vessels around important whale habitat is considered a preferential mitigation solution to other techniques (such as slowing vessels down), and the authors propose the study should be subjected to further review by the shipping industry, the IWC SC and member states of the IMO to evaluate the potential for reducing ship strikes for ASHW in the North West Indian
Publisher
IWC
Publication Year
2023
Abstract
Over eighty percent of the world’s commercially traded goods are transported by sea and increasing levels of vessels traffic in whale habitats are resulting in threats to many large whale populations. Where these overlaps occur the incidence of ship strikes resulting in injury and mortality are being reported.  Approaches to model anthropogenic space use and the spatial distribution of species are increasingly being used to identify mitigation solutions in important habitat for large whales. We developed an Ensemble Ecological Niche Model (EENM) using satellite telemetry data from Arabian Sea humpback whales (Megaptera novaeangliae; IUCN Endangered) and combined this with satellite derived Automatic ship Identification System (s-AIS) tracking data to understand the risk of ship strike within the North Indian Ocean (NIO) and Important Marine Mammal Areas (IMMAs) therein. Areas of increased relative risk to Arabian Sea humpback whales (ASHW) from commercial shipping traffic were identified close to core habitat along the Arabian Sea coast of Oman. Rerouting vessels 40 nmi (nautical miles) further offshore could reduce the risk of strike by as much as 88%. Mortalities of large whales from ship strikes and other anthropogenic causes (fisheries entanglement) are unstudied in large part because they are difficult to detect. Estimates of the potential biological removal (PBR) reveals that the ASHW population cannot sustain the human induced death of more than one animal every four years, and that the current level of threat to ASHWs from shipping is likely unsustainable, particularly for a relict population at risk of extinction. As such, development of mitigation measures is urgently required by coastal states and industry stakeholders including support from the International Maritime Organisation (IMO). Initial management measures for shipping should be expedited where threats exist within core areas of habitat and in the long-term should be implemented in parallel with a broader suite of marine spatial planning activities that accounts for the livelihoods of coastal communities and projected growth of industrial maritime activities.