ABSTRACT The 1997/98 SOWER survey in Chile searched the region from 18°30′S to 38°S. Although the... more ABSTRACT The 1997/98 SOWER survey in Chile searched the region from 18°30′S to 38°S. Although the primary intent of the surveys was to maximize blue whale encounters, survey coverage was sufficient to estimate abundance using model-based distance sampling (' ...
Antarctic blue whales are one of the endangered large baleen whales recovering from the extensive... more Antarctic blue whales are one of the endangered large baleen whales recovering from the extensive whaling pressure experienced in the 20th century. Blue whales are very vocal marine mammals capable of producing powerful sounds that can travel from a hundred to thousand or so kilometers, and these sounds can be used to estimate the relative abundance of the blue whales population. This study uses acoustic data collected from 409 of over 700 sonobuoys deployed between 1995 and 2009, on IWC research cruises (the International Decade of Cetacean Research and Southern Ocean Whale and Ecosystem Research circumpolar cruises) in the Southern Ocean south of 60oS in summer, when co-incidental visual observations of blue whales were made during line transect surveys. Blue whale presence/absence shows a high correlation between the visual and acoustic data. Both the quantity and call type of blue whale vocalisations detected from sonobuoys varied significantly between years although was depende...
Growing to 30 m long and weighing up to 163 tonnes, Antarctic blue whales, Balaenoptera musculus ... more Growing to 30 m long and weighing up to 163 tonnes, Antarctic blue whales, Balaenoptera musculus intermedia, are the largest animal that ever lived on the planet; yet despite their enormous size, they feed on small Antarctic krill (Euphausia superba). Blue whales are not easily seen at sea as their numbers are severely reduced, however, they are great sound producers and their sounds can travel hundreds to thousands of metres from the vocalizing animal. We present here an experimental design and its contribution towards improving the knowledge of Antarctic blue whale abundance, distribution and seasonal patterns.
Marine mammals, and in particular Antarctic blue whales, represent an important predator componen... more Marine mammals, and in particular Antarctic blue whales, represent an important predator component of marine ecosystems. These mammals are considered to be critically endangered due to unsustainable whaling practices in the previous century. Currently, it is also difficult to monitor the species’ population recovery through the use of sighting surveys. Passive acoustic monitoring (PAM) can be used to research Antarctic blue whales because they are quite vocal and can be detected over long distances through the use of this technology. PAM also has considerable application potential to other baleen species that reside in South African waters, including fin whales (Balaenoptera physalus). It is, however, still an emerging methodology in South Africa and a number of challenges need to be addressed before it reaches the same level of maturity as visual surveys in South Africa and around the world.
The South African Blue Whale Project is aimed at estimating the relative abundance, distribution ... more The South African Blue Whale Project is aimed at estimating the relative abundance, distribution and seasonal movements of Antarctic blue whales (Balaenoptera musculus intermedia) within the South Eastern Atlantic Ocean. As part of the project, we applied for, and received, the International Whaling Commission's International Decade of Cetacean Research/Southern Ocean Whale and Ecosystem Research (IWC IDCR/SOWER) Antarctic and low latitude acoustic recordings from sonobuoy deployments on these cruises. The examination and collation of the data resulted in the compilation of a dataset which included the sourcing and reviewing of acoustic files and the development of a database comprising both acoustic recording files and associated station data, while also removing duplicate files. Cataloguing, file reviewing and naming of the acoustic data resulted in some 7500 acoustic recording files from over 700 stations across both the IWC SOWER Antarctic cruises from 1996/1997 through to 2...
Previously published data on the occurrence of humpback whales (Megaptera novaeangliae) in the Ar... more Previously published data on the occurrence of humpback whales (Megaptera novaeangliae) in the Arabian Sea suggests that the region hosts a non-migratory population that adheres to a Northern Hemisphere breeding cycle. In order to investigate the distribution and abundance of this population, twelve small boat surveys were conducted in three main locations off the coast of Oman between February 2000 and November 2004. Humpback whales were observed during surveys in Dhofar and Gulf of Masirah on Oman’s Arabian Sea coast, but not during surveys in the Muscat region in the Gulf of Oman. An even ratio of males to females was observed and sampled during surveys in the Gulf of Masirah, which was surveyed in October and November (n = 38), while almost all whales sampled in Dhofar in February/March were male (n = 28). Song was detected frequently in the bay surrounding the Halaniyat Islands (formerly known as the Kuria Muria Bay) in February/March, but observations of mother-calf pairs were...
Humpback whales in the Arabian Sea present a possibly unique exception to the seasonal migrations... more Humpback whales in the Arabian Sea present a possibly unique exception to the seasonal migrations typical of this species. Early sightings were thought to be Southern Hemisphere whales extending their migration north of the equator. Several sources of evidence have questioned this hypothesis, suggesting that at least some whales may be year-round residents. Genetic analyses based on 11 microsatellite markers and mitochondrial DNA sequences (485bp) revealed significant differentiation between whales sampled off the coast of Oman (n=67), in the Arabian Sea, whales sampled in one North Pacific and four Southern Hemisphere regions (microsatellites, smallest F ST =0.0387, p
ABSTRACT The 1997/98 SOWER survey in Chile searched the region from 18°30′S to 38°S. Although the... more ABSTRACT The 1997/98 SOWER survey in Chile searched the region from 18°30′S to 38°S. Although the primary intent of the surveys was to maximize blue whale encounters, survey coverage was sufficient to estimate abundance using model-based distance sampling (' ...
Antarctic blue whales are one of the endangered large baleen whales recovering from the extensive... more Antarctic blue whales are one of the endangered large baleen whales recovering from the extensive whaling pressure experienced in the 20th century. Blue whales are very vocal marine mammals capable of producing powerful sounds that can travel from a hundred to thousand or so kilometers, and these sounds can be used to estimate the relative abundance of the blue whales population. This study uses acoustic data collected from 409 of over 700 sonobuoys deployed between 1995 and 2009, on IWC research cruises (the International Decade of Cetacean Research and Southern Ocean Whale and Ecosystem Research circumpolar cruises) in the Southern Ocean south of 60oS in summer, when co-incidental visual observations of blue whales were made during line transect surveys. Blue whale presence/absence shows a high correlation between the visual and acoustic data. Both the quantity and call type of blue whale vocalisations detected from sonobuoys varied significantly between years although was depende...
Growing to 30 m long and weighing up to 163 tonnes, Antarctic blue whales, Balaenoptera musculus ... more Growing to 30 m long and weighing up to 163 tonnes, Antarctic blue whales, Balaenoptera musculus intermedia, are the largest animal that ever lived on the planet; yet despite their enormous size, they feed on small Antarctic krill (Euphausia superba). Blue whales are not easily seen at sea as their numbers are severely reduced, however, they are great sound producers and their sounds can travel hundreds to thousands of metres from the vocalizing animal. We present here an experimental design and its contribution towards improving the knowledge of Antarctic blue whale abundance, distribution and seasonal patterns.
Marine mammals, and in particular Antarctic blue whales, represent an important predator componen... more Marine mammals, and in particular Antarctic blue whales, represent an important predator component of marine ecosystems. These mammals are considered to be critically endangered due to unsustainable whaling practices in the previous century. Currently, it is also difficult to monitor the species’ population recovery through the use of sighting surveys. Passive acoustic monitoring (PAM) can be used to research Antarctic blue whales because they are quite vocal and can be detected over long distances through the use of this technology. PAM also has considerable application potential to other baleen species that reside in South African waters, including fin whales (Balaenoptera physalus). It is, however, still an emerging methodology in South Africa and a number of challenges need to be addressed before it reaches the same level of maturity as visual surveys in South Africa and around the world.
The South African Blue Whale Project is aimed at estimating the relative abundance, distribution ... more The South African Blue Whale Project is aimed at estimating the relative abundance, distribution and seasonal movements of Antarctic blue whales (Balaenoptera musculus intermedia) within the South Eastern Atlantic Ocean. As part of the project, we applied for, and received, the International Whaling Commission's International Decade of Cetacean Research/Southern Ocean Whale and Ecosystem Research (IWC IDCR/SOWER) Antarctic and low latitude acoustic recordings from sonobuoy deployments on these cruises. The examination and collation of the data resulted in the compilation of a dataset which included the sourcing and reviewing of acoustic files and the development of a database comprising both acoustic recording files and associated station data, while also removing duplicate files. Cataloguing, file reviewing and naming of the acoustic data resulted in some 7500 acoustic recording files from over 700 stations across both the IWC SOWER Antarctic cruises from 1996/1997 through to 2...
Previously published data on the occurrence of humpback whales (Megaptera novaeangliae) in the Ar... more Previously published data on the occurrence of humpback whales (Megaptera novaeangliae) in the Arabian Sea suggests that the region hosts a non-migratory population that adheres to a Northern Hemisphere breeding cycle. In order to investigate the distribution and abundance of this population, twelve small boat surveys were conducted in three main locations off the coast of Oman between February 2000 and November 2004. Humpback whales were observed during surveys in Dhofar and Gulf of Masirah on Oman’s Arabian Sea coast, but not during surveys in the Muscat region in the Gulf of Oman. An even ratio of males to females was observed and sampled during surveys in the Gulf of Masirah, which was surveyed in October and November (n = 38), while almost all whales sampled in Dhofar in February/March were male (n = 28). Song was detected frequently in the bay surrounding the Halaniyat Islands (formerly known as the Kuria Muria Bay) in February/March, but observations of mother-calf pairs were...
Humpback whales in the Arabian Sea present a possibly unique exception to the seasonal migrations... more Humpback whales in the Arabian Sea present a possibly unique exception to the seasonal migrations typical of this species. Early sightings were thought to be Southern Hemisphere whales extending their migration north of the equator. Several sources of evidence have questioned this hypothesis, suggesting that at least some whales may be year-round residents. Genetic analyses based on 11 microsatellite markers and mitochondrial DNA sequences (485bp) revealed significant differentiation between whales sampled off the coast of Oman (n=67), in the Arabian Sea, whales sampled in one North Pacific and four Southern Hemisphere regions (microsatellites, smallest F ST =0.0387, p
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