Corkeron P.J.,Integrated Statistics |
Corkeron P.J.,Cornell University |
Corkeron P.J.,National Oceanic and Atmospheric Administration |
Minton G.,Environment Society of Oman |
And 6 more authors.
Endangered Species Research | Year: 2011
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. © Inter-Research 2011.
Van Bressem M.F.,Cetacean Conservation Medicine Group CMED |
Minton G.,Environment Society of Oman |
Collins T.,Wildlife Conservation Society |
Willson A.,Environment Society of Oman |
And 3 more authors.
Zoology in the Middle East | Year: 2015
The presence of tattoo-like skin disease is reported in an endangered, non-migratory subpopulation of Humpback Whales (Megaptera novaeangliae) from Oman. We examined 522 images taken during small-boat surveys in the Gulf of Masirah and in Dhofar in 2000-2006 and in 2010-2011. Tattoo-like lesions were detected in regular, good and outstanding images. They appeared as irregular or rounded, light grey marks often showing a whitish outline, and were located on the flanks, dorsum, dorsal fin and caudal peduncle. They could be relatively small to very large and cover up to an estimated 40% of the visible body surface. Over the whole study period disease prevalence reached 21.7% in 60 whales and 16.7% in 36 adults. In this category, prevalence was higher in males (26.7%, N=15) than in females (9.1%, N=11), but the difference was not significant. Lesions appeared larger in males than in the positive female and progressed in two males. Disease prevalence increased significantly from 2000 through 2011 (r2 =0.998). Advanced tattoo skin disease, with lesions extending over more than 10% of the visible body surface seemed to occur more frequently in 2010-2011 than in 2000-2006, but samples were small. This is the first confirmed report of tattoo-like disease in the Balaenopteridae family and the first time it is documented in the Arabian Sea. The disease high prevalence, its increase over time and its progression in some individuals are of concern. © 2014 Taylor and Francis.
Ponnampalam L.S.,Environment Society of Oman |
Ponnampalam L.S.,University Marine Biological Station Millport |
Ponnampalam L.S.,University of Malaya |
Collins T.J.Q.,Environment Society of Oman |
And 7 more authors.
Journal of the Marine Biological Association of the United Kingdom | Year: 2012
This study examined the stomach contents of 11 bottlenose dolphins (Tursiops sp.), five Indo-Pacific humpback dolphins (Sousa chinensis) and two spinner dolphins (Stenella longirostris) that were found stranded along the Omani coastline. Across the three species examined, a total of 4796 fish otoliths and 214 cephalopod beaks were found, representing at least 33 species in 22 families. Prey item importance was calculated using the percentage by number and percentage by frequency of occurrence methods, and a modified index of relative importance. The fish families Apogonidae, Carangidae and Scombridae were the most numerically important prey of the bottlenose dolphins. Sciaenidae was the most numerically important fish family for the Indo-Pacific humpback dolphins. The myctophid Benthosema pterotum formed the majority of the prey items of spinner dolphins. Cephalopod remains found in the stomach samples were represented by the families Sepiidae, Loliginidae and Onychoteuthidae. The known depth distribution of prey items of bottlenose dolphins indicated that the animals fed in a wide variety of habitats. Indo-Pacific humpback dolphin prey items indicated feeding in shallow coastal areas. Spinner dolphins appear to have exploited the upper 200 m of the water column for food, where their vertically migrating mesopelagic prey are found at night. Most prey species found in the stomach contents do not appear to be of current commercial importance in Oman. However, the findings here indicated that all three species of dolphins were feeding in areas where artisanal and/or commercial fishing occurs and has conservation implications. © 2012 Marine Biological Association of the United Kingdom.
Charles Anderson R.,PO Box 2074 |
Branch T.A.,University of Washington |
Alagiyawadu A.,Jetwing Lighthouse Hotel |
Baldwin R.,Environment Society of Oman |
Marsac F.,University of Cape Town
Journal of Cetacean Research and Management | Year: 2012
There is a distinct population of blue whales, Balaenoptera musculus, in the northern Indian Ocean. The taxonomie status of these animals has long been uncertain, with debate over whether this population represents a distinct subspecies, and if so which name should apply. They have most frequently been assigned to B. musculus brevicauda, but are currently considered to be B. m. indica. The movements of these blue whales within the northern Indian Ocean are poorly understood. This paper reviews catches (n = 1,288), sightings (n = 448, with a minimum of 783 animals), strandings (n = 64) and acoustic detections (n = 6 locations); uses ocean colour data to estimate seasonality of primary productivity in different areas of the northern Indian Ocean; and develops a migration hypothesis. It is suggested that most of these whales feed in the Arabian Sea off the coasts of Somalia and the Arabian peninsula during the period of intense upwelling associated with the southwest monsoon (from about May to October). At the same time some blue whales also feed in the area of upwelling off the southwest coast of India and west coast of Sri Lanka. When the southwest monsoon dies down in about October-November these upwellings cease. The blue whales then disperse more widely to eke out the leaner months of the northeast monsoon (during about December to March) in other localised areas with seasonally high productivity. These include the east coast of Sri Lanka, the waters west of the Maldives, the vicinity of the Indus Canyon (at least historically), and some parts of the southern Indian Ocean. The data are consistent with the hypothesis that at least some of the blue whales that feed off the east coast of Sri Lanka in the northeast monsoon also feed in the Arabian Sea during the southwest monsoon. These whales appear to migrate eastwards past the north of Maldives and south of Sri Lanka in about December-January, returning westwards in about April-May.
Pilcher N.J.,Marine Research Foundation |
Perry L.,World Wildlife Fund |
Antonopoulou M.,World Wildlife Fund |
Abdel-Moati M.A.,Ministry of Environment |
And 18 more authors.
Journal of Experimental Marine Biology and Ecology | Year: 2014
We present a previously unrecorded short-term behavioural response by hawksbill sea turtles to elevated sea surface temperatures in the Persian/Arabian Gulf. Surface waters typically exceed 30°C for sustained periods during the summer, and can be likened to a natural living laboratory for understanding thermoregulatory behaviour by marine species in the face of climate change and elevated global temperatures. We satellite-tracked 90 post-nesting hawksbill turtles between 2010 and 2013 as part of a larger programme to elucidate turtle foraging habitats and post-nesting behaviour. We used 66 of these datasets, where turtles clearly departed and returned to foraging grounds, for these analyses. Sea surface temperatures during the summer averaged 33.5°C and peaked at 34.9°C. During these elongated periods of elevated temperatures (June-August) the turtles temporarily migrated an average of 70km to deeper and cooler waters at northern latitudes, returning after 2-3months (September-October) back to original feeding grounds. Temperature differential T between foraging and summer loop habitats was significantly different and approximated -2°C. Turtles undertaking summer migration loops generally moved in a north-easterly direction toward deeper water, returning in a south-westerly direction to the shallower foraging grounds. Swim speeds were significantly higher and orientation was less omnidirectional during the migrations than when foraging. The outbound migrations were significantly inversely correlated with temperature, but were not linked to chlorophyll-a, geostrophic currents or sea surface height. The turtles' preference for returning to the same foraging grounds suggests a lack of other substantial influences which might have precipitated the temporary summer migration loops. Our results indicate that Gulf hawksbills employ thermoregulatory responses which take them out of high temperature and potentially physiology-threatening conditions. These findings improve our overall understanding of hawksbill habitat use and behaviour in a climate-challenged environment, and support sea turtle conservation-related policy decision-making at national and regional levels. © 2014 The Authors.