The area covered by the OWDRG survey vessel in the Dhofar 2002 survey
[Research & Fieldwork]
The Oman Whale and Dolphin Research Group (OWDRG) just recently returned from a three-week survey of the nearshore waters in the Dhofar region. The survey, conducted with support from the Ministry of Regional Municipalities, Environment and Water Resources (MRMEWR), as well as a number of local and regional businesses, yielded valuable new information about the distribution of various whale and dolphin species in the area, and provided an excellent opportunity for cooperation between the volunteer scientists and local rangers and fishermen.
The area covered by the OWDRG survey vessel in the Dhofar 2002 survey
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- Acrobatic common dolphin off the coast of Hasikiyah in the Hallaniyat Islands - |
The survey began in Salalah Port, where the OWDRG was offered extensive hospitality and logistic support by Salalah Port Services. After three days of surveying waters to the South and Southwest of Salalah, the OWDRG moved up the coast to the Mirbat peninsula, where they observed many different species of dolphins, including numerous groups of acrobatic common dolphins.
From the Mirbat Peninsula, the group moved to the Kuria Muria Bay, where they began to encounter humpback whales, one of the main target species of the survey. Previous observations indicated that the Kuria Muria Bay, which includes the Hallaniyat Islands, is used by humpback whales as a breeding ground. In an attempt to build on data gathered in surveys conducted in 2000, and 2001, the group used acoustic monitoring, skin biopsy, and photo-identification techniques to learn more about the whales' population structure and habitat use in Oman.
A hydrophone was used to record humpback whale song on numerous occasions throughout the entire bay. In other populations of humpback whales, males sing only during the breeding season, and the detection of song is used as a strong indicator of breeding activity. Although no calves were observed during this survey, it is possible that the males were the first to arrive to the area, announcing their presence and their intentions with their song.
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- The dorsal fin of 'Flatfin', a humpback whale - |
Humpback whale song is population specific and is used by some scientists to define discreet populations. All the males in one population will sing the same song, which can last 20 minutes, and contain a number of identifiable themes that are repeated in a structured manner. The song recorded by the OWDRG can be compared with song from other known populations in neighbouring regions, to determine whether there has been any exchange of themes between populations, or whether the Omani song has developed in isolation. Another way of determining whether the Omani population is isolated, or still in contact with other neighbouring populations, is by conducting genetic analysis on skin samples collected from the whales. Comparing the DNA of Omani whales with that of whales from neighbouring populations on the East Coast of Africa will allow scientists to learn whether the two populations are interbreeding. Genetic analysis will also allow the researchers to determine whether whales that were observed and sampled are male or female, and how whales that were observed together are related to each other. During the survey, skin samples were collected from 8 whales. These will be added to the 20 samples collected on previous surveys in 2001, and should yield some preliminary results to be presented at the next meeting of the International Whaling Commission (IWC) in Japan in May of this year.
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- The tail flukes of 'Chomp', a humpback whale - |
Photos were taken of each whale's dorsal fin and tail flukes as a way of recognising individual whales and tracking their movements over time. Of the 17 sightings of humpback whales logged during this survey, at least 4 sightings were 're-sights' of known individuals. One individual, nicknamed 'Flatfin' was photographed for the first time off the South coast of Barr al Hikmann in October 2000, and twice during the February 2002 survey. Another individual, affectionately known as 'Chomp' because of the bite-shaped notch in it's tail flukes, has now been observed on 4 separate occasions in the past 15 months: first in Muscat in December 2000, then in Dhofar in February 2001, again in Masirah in October 2001, and yet again off the coast of Hadbin on February 28th, 2002. Re-sights like these help the OWDRG to learn about the whales' seasonal movements. Coupled with the results of acoustic and genetic analysis, they will help to build a better understanding of Oman's population of humpback whales.
Valuable observations were also made of a number of other whale and dolphin species, including common, spinner, bottlenose, Risso's and Indo-Pacific humpback dolphins ad well as Bryde's and Sperm whales. Beach-caste specimens of skeletal material from false killer whales, bottlenose, common and Indo-Pacific humpback dolphins were also collected and will be curated at the Oman Natural History Museum where they will be available for future study.
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- Tim and Adil al Shahari, listening to humpback songs - |
While working in the Dhofar region, members of the OWDRG were able to cooperate closely with the local rangers of Hallaniyah and Hasik, including them in boat surveys, and meeting with them in the evenings while processing data and photographs on the computer. Staff from the Raysut Marine Laboratory, a division of the Ministry of Agriculture and Fisheries, were also involved in boat surveys and the OWDRG talked extensively with local fishermen and government officials, sharing digital photographs and charts to explain the nature of their work and providing a valuable opportunity to exchange experience, knowledge and ideas.
The OWDRG would not be able to conduct these valuable surveys without the support of local and regional businesses. Although many different sponsors have supported the group's work in the past, particular thanks for this survey are owed to: Ford Middle East, Shell Oman Marketing, Salalah Port Services, Veritas Geophysical, Truck Oman, W.S. Atkins, Emirates Airlines, Han Padron Associates, Tawoos, DHL, OHI Marine, and Five Oceans L.L.C.
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- Humpback whale tail flukes at sunset - |