Oman Arabian Sea IMMA

Size in Square Kilometres

96 146 km2

Qualifying Species and Criteria

Humpback whale – Megaptera novaeangliae

Criterion A; B (2); C (3)

Marine Mammal Diversity 

Balaenoptera acutorostrata, Balaenoptera edeni, Balaenoptera musculus indica, Delphinus delphis tropicalis, Globicephala macrorhynchus, Grampus griseus, Kogia Breviceps, Kogia Sima, Orcinus orca, Peponocephala electra, Physeter macrocephalus, Pseudorca crassidens, Sousa plumbea, Stenella longirostris, Steno bredanensis, Tursiops aduncus, Tursiops truncatus, Ziphius cavirostris

Summary

The Arabian Sea humpback whale subpopulation is the only known population of humpback whales (Megaptera novaeangliae) that does not migrate between low-latitude breeding grounds and high latitude feeding grounds.  Dedicated cetacean surveys of Oman’s Arabian Sea coastline, conducted from 2000 onward have confirmed that these whales are genetically distinct and geographically isolated, and thus represent a highly distinct sub-population, which is designated as Endangered on the IUCN Red List of Threatened Species. Boat-based surveys, acoustic surveys, satellite telemetry and photo-identification indicate that this IMMA encompasses the most important habitat for Oman’s Arabian Sea humpback whales.  Whales mate, calve, feed and travel in this area, with the Gulf of Masirah IMMA more strongly associated with feeding, and the Dhofar IMMA more strongly associated with reproduction.  This larger IMMA  encompasses these two smaller IMMAS as well as the wider corridor connecting them.  It also includes the zone to the north of Masirah Island that has not been well surveyed, but where numerous anecdotal reports and some strandings of humpback whales have been documented.

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

The Arabian Sea humpback whale sub-population is listed as ‘Endangered’ on the International Union for the Conservation of Nature (IUCN) Red List based on a mark-recapture population estimate of 82 individuals (95% CI 60-111; Minton et al. 2008), as well as the sub-population’s documented genetic distinctiveness and isolation from other neighbouring sub-populations in the Indian Ocean (Pomilla et al., 2014). While the Dhofar region (Hallaniyats Bay) and the Gulf of Masirah (GOM) have been identified as core hotspots for feeding and reproduction, Arabian Sea humpback whales (Megaptera novaeangliae) have been documented using almost the full range of this humpback highway through direct observation during dedicated cetacean surveys, satellite tracking and passive acoustic monitoring (Minton et al. 2011; Baldwin et al. 2011; Willson et al. 2012; Willson et al. 2013; Willson et al. 2014; Willson et al. 2015; ESO, 2019; Cerchio et al. 2016, Cerchio et al. 2018)

Criterion B: Distribution and Abundance

Sub-criterion B2: Aggregations

The Arabian Sea humpback whale subpopulation is the only known population of humpback whales that does not engage in a large-scale migration between low-latitude breeding grounds and high latitude feeding grounds.  It is genetically distinct and geographically isolated, and thus represents a highly distinct sub-population. Boat-based surveys coupled with acoustic surveys, satellite telemetry and photo-identification studies indicate that the Oman Arabian Sea Coast EBSA, with slightly expanded boundaries, encompasses the most important habitat for Oman’s Arabian Sea humpback whales.  While two of 14 tagged whales left the boundaries of the area, the majority stayed within these boundaries throughout the duration of their tag transmission (Willson et al. 2016, 2018).  Furthermore, a high rate of photo-identification re-sights between the Gulf of Masirah and Dhofar both within years and between years indicates that while some whales may engage in longer-range movements to Yemen and/or India, at least a portion of the sub-population seems to remain on the Arabian Sea coast of Oman year-round and in multiple years (Minton et al. 2011, Willson et al. 2016, 2018).  Additionally, mark-recapture estimates based on the same photo-identification data collected off the coast of Oman between 2000 and 2004 indicate that fewer than 100 individuals were using the habitats encompassed in the area (Minton et al. 2008; Minton et al 2011.). Modelling of humpback whale sightings data in relation to survey effort using spatial eigenvector filtering to account for spatial autocorrelation, as well as results of satellite telemetry studies, confirm that the higher relative densities of whales in the Dhofar and Gulf of Masirah areas a reflection of their behaviour and not only survey effort (Corkeron et al. 2011, Willson et al. 2016, 2017, 2018). The aggregations have been associated with feeding and breeding behaviour and in one survey period these activities were observed concurrently (Baldwin et al. 2011; Willson et al.2011).  While densities of whales in these areas may be lower than those on other humpback whale breeding and feeding grounds, the densities recorded here are higher than any other area in the Arabian Sea humpback whales’ range to date, and the areas clearly serve the same purpose as feeding and breeding grounds do for the species elsewhere.

Criterion C: Key Life Cycle Activities

Sub-criterion C3: Migration Routes

Location and track data derived from the satellite telemetry revealed a predominance of localized behaviour and transits between the Hallaniyats Bay area and the Gulf of Masirah. Transitory movements of humpback whales through the Dhofar area have been revealed by behaviour mode index of static space state modelling of satellite telemetry data. These records are noted from five of 14 Arabian Sea humpback whales instrumented with tags in the Dhofar and Gulf of Masirah areas between 2014 and 2015 (Willson et al. 2016). Habitat utilization kernel density estimates indicate high site fidelity for the majority of tagged individuals (Willson et al., 2016, Willson et al., 2015, Willson et al., 2018).  Only two of the 14 tagged individuals moved outside of Omani waters and the area bounded by this area. Of these two, one male, remained mostly within the boundaries of the area but moved further southwest into Yemeni waters. The other, a female, crossed the Arabian Sea to the southern tip of India, but then returned to the Gulf of Masirah where she was originally tagged (Willson et al., 2016, Willson et al., 2018). The documented movement between Oman and India, coupled with an increasing number of sightings and recordings of song documented from the coasts of Pakistan and India, provides evidence that some proportion of the Arabian Sea humpback whale population is using the eastern portion of the Arabian Sea as well as Oman’s coast. The Oman Arabian Sea area encompasses the most heavily used habitat for whales that are present, year-around, off of Oman’s coast.

Supporting Information

Baldwin, R., Collins, T., Minton, G., Willson, A., Corkeron, P. 2011. Arabian Sea Humpback Whales 2011 Update: Resights, bubble feeding and hotspots. Paper presented to the International Whaling Commission Scientific Committee, May 2011. SC/63/SH27.

Cerchio, S., A. Willson, C. Muirhead, S. Al Harthi, R. Baldwin, M. Bonato, T. Collins, J. Di Clemente, V. Dulau, V. Estrade, G. Latha, A. G. Minton, and M. Sarrouf Willson. 2018. Geographic variation in song indicates both isolation of Arabian Sea humpback whales and presence of Southern Hemisphere whales off Oman. IWC/SC67B/CMP19, Paper presented to the International Whaling Commission Scientific Committee, Bled, Slovenia.

Cerchio, S., A. Willson, C. Muirhead, G. Minton, T. Collins, R. Baldwin, M. Sarrouf Willson, and S. Al Harthi. 2016. Preliminary Report on Long-term Detection of Arabian Sea Humpback Whale Vocalizations off Oman, SC/66b/SH/32 Paper presented to the International Whaling Commission Scientific Committee, Bled, Slovenia.

Corkeron, P. J., G. M. T. Collins, K. Findlay, A. Willson, and R. Baldwin. 2011. Spatial models of sparse data to inform cetacean conservation planning: an example from Oman. Endangered Species Research 15(1):39-52.

Environment Society of Oman. 2019. Oman Cetacean Database, (OMCD). OMCD Ver20160527-Update20170411. Accessed 3/8/2019.

Minton, G., T. J. Q. Collins, K. P. Findlay, P. J. Ersts, H. C. Rosenbaum, P. Berggren, and R. M. Baldwin. 2011. Seasonal distribution, abundance, habitat use and population identity of humpback whales in Oman. Journal of Cetacean Research and Management Special Issue on Southern Hemisphere Humpback Whales(3):185–198.

Minton, G., T. J. Q. Collins, C. Pomilla, K. P. Findlay, H. C. Rosenbaum, R. Baldwin, and R. L. Brownell Jr. 2008. Megaptera novaeangliae, Arabian Sea subpopulation. IUCN Red List of Threatened Species http://www.iucnredlist.org/details/132835

Pomilla, C., A. R. Amaral, T. Collins, G. Minton, K. Findlay, M. S. Leslie, L. Ponnampalam, R. Baldwin, and H. Rosenbaum. 2014. The World’s Most Isolated and Distinct Whale Population? Humpback Whales of the Arabian Sea. PLoS ONE 9(12):e114162. doi: 10.1371/journal.pone.0114162

Willson, A., Baldwin, R., Minton, G. and Collins, T. 2012. Arabian Sea humpback whale research update for 2011/2012. Paper SC/64/SH30 presented to the International Whaling Commission Scientific Committee, Panama

Willson, A., Baldwin, R., Minton, G., Gray, H., Findlay, K., Collins, T.  2013. Arabian Sea humpback whale research update for 2012/13. Paper SC/65a/SH06 presented to the International Whaling Commission Scientific Committee, Jeju, South Korea.

Willson, A., Baldwin, R., Cerchio, S., Geyer, Y., Godley B., Gray, H., Al-Harthi, S., Minton, Al-Zehlawi, N., M.Witt., Rosenbaum, H., Zerbini, A. 2014. Preliminary results and first insights from satellite tracking studies of male Arabian Sea humpback whales. Paper SC/65b/SH19 presented to the International Whaling Commission Scientific Committee, Slovenia.

Willson, A., R. Baldwin, S. Cerchio, T. Collins, K. Findlay, H. Gray, B. J. Godley, S. Al Harthi, A. Kennedy, G. Minton, F. Sucunza, A. N. Zerbini, and M. J. Witt. 2016. Research update on satellite tagging studies of the Arabian Sea humpback whales in the Sultanate of Oman, Paper SC/66b/SH/28 presented to the International Whaling Commission Scientific Committee, Bled, Slovenia.

Willson, A., R. Baldwin, S. Cerchio, T. Collins, K. Findlay, H. Gray, B. J. Godley, S. Al Harthi, A. Kennedy, G. Minton, A. N. Zerbini, and M. J. Witt. 2015. Research update of satellite tracking studies of male Arabian Sea humpback whales; Oman. Paper SC/66a/SH/22 Rev 1, presented to the International Whaling Commission Scientific Committee, San Diego.

Willson, A., M. Leslie, R. Baldwin, S. Cerchio, S. Childerhouse, T. collins, K. Findlay, T. Genov, B. J. Godley, S. Al Harthi, D. W. Macdonald, A. G. Minton, A. Zerbini, and M. J. Witt. 2018. Update on satellite telemetry studies and first unoccupied aerial vehicle assisted health assessment studies of Arabian Sea humpback whales off the coast of Oman.  Report IWC/SC67B/CMP13Rev1 presented to the International Whaling Commission Scientific Committee. Bled, Slovenia

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