Ken Findlay | University of Pretoria (original) (raw)
Papers by Ken Findlay
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 (' ...
The presence of southern right whales (Eubalaena australis) along the coast of Mozambique has not... more The presence of southern right whales (Eubalaena australis) along the coast of Mozambique has not been recorded since the close of commercial whaling in 1923. This paper describes ten sightings (5 'confirmed' and 5 'probable') made from landbased observations, boat-based 'single-day' surveys as well as land-based and inshore boat-based incidental sightings between 1997 and 2009. The number of sightings increased over the 1997 and 2009 time period and occurred only during August and September. On one occasion, a mother-calf pair was recorded. We also describe an interaction between a southern right whale and humpback whale, which was observed on at least two days. These recent sightings confirm that southern right whales have resumed visiting the coast of Mozambique, albeit in probably very low numbers.
Journal of Cetacean Research and Management
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...
Journal of Cetacean Research and Management
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
Journal of Cetacean Research and Management
The photo-identification catalogue of humpback whale tail flukes from Oman was compared with thos... more The photo-identification catalogue of humpback whale tail flukes from Oman was compared with those from Antongil Bay, Madagascar and study sites in South Africa and Mozambique collectively termed the 'East African Mainland'. No matches were found, supporting other lines of evidence that the humpback whales studied off the coast of Oman form part of a discrete Arabian Sea population, which adheres to a Northern Hemisphere breeding cycle, and has little or no ongoing exchange with the nearest neighbouring populations in the southern Indian Ocean. While the sample size from Oman is small, and low levels of ongoing exchange might not be detected in this type of catalogue comparison, the study nonetheless emphasises the need to pursue research and conservation efforts in the known and suspected range of the Endangered Arabian Sea humpback whale population.
Humpback whales (Megaptera novaeangliae) of the Southern Hemisphere are separated by the Internat... more Humpback whales (Megaptera novaeangliae) of the Southern Hemisphere are separated by the International Whaling Commission (IWC) into seven Wintering Regions (A-G) based on tropical distribution. To evaluate the biological significance of these stock subdivisions, an analysis of nuclear genetic markers was conducted for the South Atlantic (Regions A and B), and the southwestern and northern Indian (Regions C and X) Oceans. A total of 1,531 individual whales representing ten sampling sites within these regions were genotyped at eleven microsatellite loci. A hierarchical analysis of molecular variance using F ST or R ST estimators supported differentiation among the regions, although the degree of substructure was low. When contiguous wintering regions were tested the most differentiated were Regions X and C, followed by Regions A and B, and finally the least differentiated Regions B and C. A Bayesian clustering procedure was however unable to partition the individuals into different groups, with the exception of Region X which formed a separate cluster. Overall the level of structure observed was considerably lower than the one previously detected with mtDNA. In most cases microsatellite F ST estimates showed more structure in females when compared to the males or to the entire population, with some exceptions where females seems to preferentially use some localities. Although some support was encountered for further sub-divisions within Regions B and C, the divisions supported do not correspond to the ones currently in use. Estimates of dispersal rates revealed high numbers of effective migrants per generation exchanged between contiguous wintering regions, as well as within regions. The direct detection of movements by genetically identified individuals, confirm that gene flow is ongoing across some of the present boundaries.
Insights in the variation in pigmentation patterns and other external features in Hyperoodon plan... more Insights in the variation in pigmentation patterns and other external features in Hyperoodon planifrons are few, in particular, variability contributed by each of individual, ontogenetic, sexual, and geographic factors. A preliminary assessment is based on two close-up sightings of juveniles during IWC-SOWER Cruises and stranded specimens from South Africa, Australia and New Zealand. Bold, cream-white facial fields separated by a distinct dark blowhole stripe are diagnostic of all juveniles/neonates examined and may persist in subadults. Dark eyepatches may be pronounced or almost absent, a light nuchal band behind the blowhole may be prominent or muted, and the dorsal aspect of flippers may be light or dark. A light flank patch on the tailstock is consistent in juveniles. With maturation the head pattern gradually blurs, apparently because facial fields and the nuchal band gain pigmentation. The slate-grey or dark brownish-grey spinal field in juveniles is appreciably darker than in most adults, in which it varies widely, ranging from brownish-grey (most common), bluish-black to yellowish. Diatoms have been blamed as cause for the brown hue, however the evidence is unclear. Large, almost-white animals have been reported but no such specimens were available for study. Much of the external variation seen may be individual and ontogenetic, however sexual dimorphism and geographic variation remain unassessed due to small samples. A comprehensive morphological study is indicated. The bold features in juvenile H. planifrons are diagnostically distinct from juvenile Tasmacetus shepherdi and Indopacetus pacificus. Non-priority status and long dive durations have allowed scant time for data collection on H. planifrons during Antarctic surveys. This study shows that maximizing opportunistic encounters through allowance for some flexibility in schedules, valuable data can be obtained. A rule-of-thumb is recommended for avoiding ziphiid species identification at distances exceeding 0.8 nmiles.
Twenty-eight odontocete species were identified as occupying sub-Antarctic and Antarctic habitat ... more Twenty-eight odontocete species were identified as occupying sub-Antarctic and Antarctic habitat covered by the 1994 IWC-established Southern Ocean Sanctuary. Toothed whales evidently play an important part in the Antarctic polar ecosystem. Twenty-two species are autochthonous in showing a regular, apparently year-round, presence in the Sanctuary: Physeter Mesoplodon bowdoini and Mesoplodon hectori. Six species are considered vagrants into the Sanctuary: Kogia sima, Grampus griseus, Steno bredanensis, Mesoplodon peruvianus, Mesoplodon densirostris and Mesoplodon mirus. However, vagrant status of these three mesoplodonts is only provisionally assigned, considering that improved knowledge of diagnostic features of beaked whales should, as in recent years, continue to facilitate at-sea identification. Two species are considered as having a 'contiguous' range (records less than 2° north of Sanctuary boundaries): Mesoplodon ginkgodens (at 39°S) and Mesoplodon mirus (at 38°24'S). The habitual southern range of at least four odontocetes extends significantly farther poleward than expected. G. melas edwardii is regularly encountered south of the Antarctic Polar Front, much like M. grayi which is known to reach the Ross Sea ice edge (ca. 67°S). Z. cavirostris and L. obscurus cross the Polar Front occasionally. The distribution of M. peruvianus and M. traversii and their relation to SST are unclear. Their southernmost records, 42°31'S and 44°17'S respectively, may either be extralimital or, more likely, reflect ordinary austral range. Temporally non-aligned distribution patterns of Hyperoodon planifrons in Antarctic and South African waters may suggest stock segregation.
Marine Ecology Progress Series, 1998
The distribution and seasonality of humpback whales Megaptera novaeangliae in the southwest India... more The distribution and seasonality of humpback whales Megaptera novaeangliae in the southwest Indian Ocean are investigated from a number of sources. These include sighting and acoustic data collected on shore-based surveys on the African coast and from dedicated ship-based surveys in the coastal waters of ~Mozambique. Madagascar, across the Mozambique Channel and along the Madagascar Ridge, plus a e r~a l sighting data from the Durban (South Africa) whaling ground, historical catch data by 10 d period for whahng operations at Durban, Linga Linga (1\4ozamblque) and Madagascar, and Incldental sightings data from a research s h~p and transitlng merchant vessel.
Endangered Species Research, 2011
Habitat models are tools for understanding the relationship between cetaceans and their environme... more Habitat models are tools for understanding the relationship between cetaceans and their environment, from which patterns of the animals' space use can be inferred and management strategies developed. Can working with space use alone be sufficient for management, when habitat cannot be modeled? Here, we analyzed cetacean sightings data collected from small boat surveys off the coast of Oman between 2000 and 2003. The waters off Oman are used by the Endangered Arabian Sea population of humpback whales. Our data were collected primarily for photo-identification, using a haphazard sampling regime, either in areas where humpback whales were thought to be relatively abundant, or in areas that were logistically easy to survey. This leads to spatially autocorrelated data that are not amenable to analysis using standard approaches. We used quasi-Poisson generalized linear models and semi-parametric spatial filtering to assess the distribution of humpback and Bryde's whales in 3 areas off Oman relative to 3 simple physiographic variables in a survey grid. Our analysis focused on the spatial eigenvector filtering of models, coupled with the spatial distribution of model residuals, rather than just on model predictions. Spatial eigenvector filtering accounts for spatial autocorrelation in models, allowing inference to be made regarding the relative importance of particular areas. As an exemplar of this approach, we demonstrate that the Dhofar coast of southern Oman is important habitat for the Arabian Sea population of humpback whales. We also suggest how conservation planning for mitigating impacts on humpback whales off the Dhofar coast could start.
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 (' ...
The presence of southern right whales (Eubalaena australis) along the coast of Mozambique has not... more The presence of southern right whales (Eubalaena australis) along the coast of Mozambique has not been recorded since the close of commercial whaling in 1923. This paper describes ten sightings (5 'confirmed' and 5 'probable') made from landbased observations, boat-based 'single-day' surveys as well as land-based and inshore boat-based incidental sightings between 1997 and 2009. The number of sightings increased over the 1997 and 2009 time period and occurred only during August and September. On one occasion, a mother-calf pair was recorded. We also describe an interaction between a southern right whale and humpback whale, which was observed on at least two days. These recent sightings confirm that southern right whales have resumed visiting the coast of Mozambique, albeit in probably very low numbers.
Journal of Cetacean Research and Management
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...
Journal of Cetacean Research and Management
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
Journal of Cetacean Research and Management
The photo-identification catalogue of humpback whale tail flukes from Oman was compared with thos... more The photo-identification catalogue of humpback whale tail flukes from Oman was compared with those from Antongil Bay, Madagascar and study sites in South Africa and Mozambique collectively termed the 'East African Mainland'. No matches were found, supporting other lines of evidence that the humpback whales studied off the coast of Oman form part of a discrete Arabian Sea population, which adheres to a Northern Hemisphere breeding cycle, and has little or no ongoing exchange with the nearest neighbouring populations in the southern Indian Ocean. While the sample size from Oman is small, and low levels of ongoing exchange might not be detected in this type of catalogue comparison, the study nonetheless emphasises the need to pursue research and conservation efforts in the known and suspected range of the Endangered Arabian Sea humpback whale population.
Humpback whales (Megaptera novaeangliae) of the Southern Hemisphere are separated by the Internat... more Humpback whales (Megaptera novaeangliae) of the Southern Hemisphere are separated by the International Whaling Commission (IWC) into seven Wintering Regions (A-G) based on tropical distribution. To evaluate the biological significance of these stock subdivisions, an analysis of nuclear genetic markers was conducted for the South Atlantic (Regions A and B), and the southwestern and northern Indian (Regions C and X) Oceans. A total of 1,531 individual whales representing ten sampling sites within these regions were genotyped at eleven microsatellite loci. A hierarchical analysis of molecular variance using F ST or R ST estimators supported differentiation among the regions, although the degree of substructure was low. When contiguous wintering regions were tested the most differentiated were Regions X and C, followed by Regions A and B, and finally the least differentiated Regions B and C. A Bayesian clustering procedure was however unable to partition the individuals into different groups, with the exception of Region X which formed a separate cluster. Overall the level of structure observed was considerably lower than the one previously detected with mtDNA. In most cases microsatellite F ST estimates showed more structure in females when compared to the males or to the entire population, with some exceptions where females seems to preferentially use some localities. Although some support was encountered for further sub-divisions within Regions B and C, the divisions supported do not correspond to the ones currently in use. Estimates of dispersal rates revealed high numbers of effective migrants per generation exchanged between contiguous wintering regions, as well as within regions. The direct detection of movements by genetically identified individuals, confirm that gene flow is ongoing across some of the present boundaries.
Insights in the variation in pigmentation patterns and other external features in Hyperoodon plan... more Insights in the variation in pigmentation patterns and other external features in Hyperoodon planifrons are few, in particular, variability contributed by each of individual, ontogenetic, sexual, and geographic factors. A preliminary assessment is based on two close-up sightings of juveniles during IWC-SOWER Cruises and stranded specimens from South Africa, Australia and New Zealand. Bold, cream-white facial fields separated by a distinct dark blowhole stripe are diagnostic of all juveniles/neonates examined and may persist in subadults. Dark eyepatches may be pronounced or almost absent, a light nuchal band behind the blowhole may be prominent or muted, and the dorsal aspect of flippers may be light or dark. A light flank patch on the tailstock is consistent in juveniles. With maturation the head pattern gradually blurs, apparently because facial fields and the nuchal band gain pigmentation. The slate-grey or dark brownish-grey spinal field in juveniles is appreciably darker than in most adults, in which it varies widely, ranging from brownish-grey (most common), bluish-black to yellowish. Diatoms have been blamed as cause for the brown hue, however the evidence is unclear. Large, almost-white animals have been reported but no such specimens were available for study. Much of the external variation seen may be individual and ontogenetic, however sexual dimorphism and geographic variation remain unassessed due to small samples. A comprehensive morphological study is indicated. The bold features in juvenile H. planifrons are diagnostically distinct from juvenile Tasmacetus shepherdi and Indopacetus pacificus. Non-priority status and long dive durations have allowed scant time for data collection on H. planifrons during Antarctic surveys. This study shows that maximizing opportunistic encounters through allowance for some flexibility in schedules, valuable data can be obtained. A rule-of-thumb is recommended for avoiding ziphiid species identification at distances exceeding 0.8 nmiles.
Twenty-eight odontocete species were identified as occupying sub-Antarctic and Antarctic habitat ... more Twenty-eight odontocete species were identified as occupying sub-Antarctic and Antarctic habitat covered by the 1994 IWC-established Southern Ocean Sanctuary. Toothed whales evidently play an important part in the Antarctic polar ecosystem. Twenty-two species are autochthonous in showing a regular, apparently year-round, presence in the Sanctuary: Physeter Mesoplodon bowdoini and Mesoplodon hectori. Six species are considered vagrants into the Sanctuary: Kogia sima, Grampus griseus, Steno bredanensis, Mesoplodon peruvianus, Mesoplodon densirostris and Mesoplodon mirus. However, vagrant status of these three mesoplodonts is only provisionally assigned, considering that improved knowledge of diagnostic features of beaked whales should, as in recent years, continue to facilitate at-sea identification. Two species are considered as having a 'contiguous' range (records less than 2° north of Sanctuary boundaries): Mesoplodon ginkgodens (at 39°S) and Mesoplodon mirus (at 38°24'S). The habitual southern range of at least four odontocetes extends significantly farther poleward than expected. G. melas edwardii is regularly encountered south of the Antarctic Polar Front, much like M. grayi which is known to reach the Ross Sea ice edge (ca. 67°S). Z. cavirostris and L. obscurus cross the Polar Front occasionally. The distribution of M. peruvianus and M. traversii and their relation to SST are unclear. Their southernmost records, 42°31'S and 44°17'S respectively, may either be extralimital or, more likely, reflect ordinary austral range. Temporally non-aligned distribution patterns of Hyperoodon planifrons in Antarctic and South African waters may suggest stock segregation.
Marine Ecology Progress Series, 1998
The distribution and seasonality of humpback whales Megaptera novaeangliae in the southwest India... more The distribution and seasonality of humpback whales Megaptera novaeangliae in the southwest Indian Ocean are investigated from a number of sources. These include sighting and acoustic data collected on shore-based surveys on the African coast and from dedicated ship-based surveys in the coastal waters of ~Mozambique. Madagascar, across the Mozambique Channel and along the Madagascar Ridge, plus a e r~a l sighting data from the Durban (South Africa) whaling ground, historical catch data by 10 d period for whahng operations at Durban, Linga Linga (1\4ozamblque) and Madagascar, and Incldental sightings data from a research s h~p and transitlng merchant vessel.
Endangered Species Research, 2011
Habitat models are tools for understanding the relationship between cetaceans and their environme... more Habitat models are tools for understanding the relationship between cetaceans and their environment, from which patterns of the animals' space use can be inferred and management strategies developed. Can working with space use alone be sufficient for management, when habitat cannot be modeled? Here, we analyzed cetacean sightings data collected from small boat surveys off the coast of Oman between 2000 and 2003. The waters off Oman are used by the Endangered Arabian Sea population of humpback whales. Our data were collected primarily for photo-identification, using a haphazard sampling regime, either in areas where humpback whales were thought to be relatively abundant, or in areas that were logistically easy to survey. This leads to spatially autocorrelated data that are not amenable to analysis using standard approaches. We used quasi-Poisson generalized linear models and semi-parametric spatial filtering to assess the distribution of humpback and Bryde's whales in 3 areas off Oman relative to 3 simple physiographic variables in a survey grid. Our analysis focused on the spatial eigenvector filtering of models, coupled with the spatial distribution of model residuals, rather than just on model predictions. Spatial eigenvector filtering accounts for spatial autocorrelation in models, allowing inference to be made regarding the relative importance of particular areas. As an exemplar of this approach, we demonstrate that the Dhofar coast of southern Oman is important habitat for the Arabian Sea population of humpback whales. We also suggest how conservation planning for mitigating impacts on humpback whales off the Dhofar coast could start.