Willson, A.,Baldwin, R.,Collins, T.,Godley, B.J.,Minton, G.,Al Harthi, S.,Pikesley, Stephen K,Witt, Matthew J
Preliminary ensemble ecological niche modelling of Arabian Sea humpback whale vessel sightings and satellite telemetry data Technical Report
no. 502, 2017, ISBN: SC/67A/CMP/15.
Abstract | BibTeX | Tags: Arabian Gulf, Arabian Sea, ensemble niche modeling, habitat modelling, habitat preference, Humpback Whale, megaptera novaeangliae, Persian Gulf, Satellite telemetry
@techreport{,
title = {Preliminary ensemble ecological niche modelling of Arabian Sea humpback whale vessel sightings and satellite telemetry data},
author = {Willson, A.,Baldwin, R.,Collins, T.,Godley, B.J.,Minton, G.,Al Harthi, S.,Pikesley, Stephen K,Witt, Matthew J},
issn = { SC/67A/CMP/15},
year = {2017},
date = {2017-01-01},
journal = {Document presented to the meeting of the Scientific Committee of the International Whaling Commission},
number = {502},
pages = {17},
abstract = {Ensemble ecological niche modelling (EENM) can provide insight into the relationship between marine mammals and
their environment and can predict distribution beyond the range of observed locations. The technique can be used to
identify sites for future field research and guide conservation and management activities. The spatial ecology of Arabian
Sea humpback whales (ASHWs) has been described off the coast of Oman, although a paucity of information exists
from which to describe their distribution across the rest of their potential range. Here we present an ensemble ecological
niche modelling framework to predict habitat suitability of ASHWs across the north Indian Ocean. Sightings data from
Oman-based small vessel surveys (2003-2014) and satellite telemetry records (2014-2016) were used along with
environmental co-variate data from a season between December and May. Net primary productivity featured as the only
co-variate with a strong influence on models for both datasets. Model test evaluation metrics scored >0.9, and mapped
outputs of likely distribution highlighted spatial similarity across multiple models. Telemetry data predicted suitable
habitat to be further offshore than the models derived from sightings data. All resulting distribution maps described
areas of high suitability (index value <0.75) along the southern and central coast of Oman and of the northern Arabian
Sea between the Gulf of Kutch and sub-marine canyon features off the Indus delta. There was good spatial concordance
between ensemble model predictions with actual locations of Soviet catches of humpback whales in the northern Indian
Ocean between 1964 and 1966. Both the telemetry and the sightings data were temporally sporadic in their coverage
(across months) and biologically biased (towards males) and as such results from our preliminary efforts should be
considered in light of these caveats. However, these preliminary results are valuable and indicate likely co-occurrence
with high density shipping traffic routes in the region and target additional areas for focussed field surveys. Results
from this study should be considered together with results of recent north Indian Ocean blue whale ENM studies to help
guide future research and conservation management objectives in the region.},
keywords = {Arabian Gulf, Arabian Sea, ensemble niche modeling, habitat modelling, habitat preference, Humpback Whale, megaptera novaeangliae, Persian Gulf, Satellite telemetry},
pubstate = {published},
tppubtype = {techreport}
}
Ensemble ecological niche modelling (EENM) can provide insight into the relationship between marine mammals and
their environment and can predict distribution beyond the range of observed locations. The technique can be used to
identify sites for future field research and guide conservation and management activities. The spatial ecology of Arabian
Sea humpback whales (ASHWs) has been described off the coast of Oman, although a paucity of information exists
from which to describe their distribution across the rest of their potential range. Here we present an ensemble ecological
niche modelling framework to predict habitat suitability of ASHWs across the north Indian Ocean. Sightings data from
Oman-based small vessel surveys (2003-2014) and satellite telemetry records (2014-2016) were used along with
environmental co-variate data from a season between December and May. Net primary productivity featured as the only
co-variate with a strong influence on models for both datasets. Model test evaluation metrics scored >0.9, and mapped
outputs of likely distribution highlighted spatial similarity across multiple models. Telemetry data predicted suitable
habitat to be further offshore than the models derived from sightings data. All resulting distribution maps described
areas of high suitability (index value <0.75) along the southern and central coast of Oman and of the northern Arabian
Sea between the Gulf of Kutch and sub-marine canyon features off the Indus delta. There was good spatial concordance
between ensemble model predictions with actual locations of Soviet catches of humpback whales in the northern Indian
Ocean between 1964 and 1966. Both the telemetry and the sightings data were temporally sporadic in their coverage
(across months) and biologically biased (towards males) and as such results from our preliminary efforts should be
considered in light of these caveats. However, these preliminary results are valuable and indicate likely co-occurrence
with high density shipping traffic routes in the region and target additional areas for focussed field surveys. Results
from this study should be considered together with results of recent north Indian Ocean blue whale ENM studies to help
guide future research and conservation management objectives in the region.
their environment and can predict distribution beyond the range of observed locations. The technique can be used to
identify sites for future field research and guide conservation and management activities. The spatial ecology of Arabian
Sea humpback whales (ASHWs) has been described off the coast of Oman, although a paucity of information exists
from which to describe their distribution across the rest of their potential range. Here we present an ensemble ecological
niche modelling framework to predict habitat suitability of ASHWs across the north Indian Ocean. Sightings data from
Oman-based small vessel surveys (2003-2014) and satellite telemetry records (2014-2016) were used along with
environmental co-variate data from a season between December and May. Net primary productivity featured as the only
co-variate with a strong influence on models for both datasets. Model test evaluation metrics scored >0.9, and mapped
outputs of likely distribution highlighted spatial similarity across multiple models. Telemetry data predicted suitable
habitat to be further offshore than the models derived from sightings data. All resulting distribution maps described
areas of high suitability (index value <0.75) along the southern and central coast of Oman and of the northern Arabian
Sea between the Gulf of Kutch and sub-marine canyon features off the Indus delta. There was good spatial concordance
between ensemble model predictions with actual locations of Soviet catches of humpback whales in the northern Indian
Ocean between 1964 and 1966. Both the telemetry and the sightings data were temporally sporadic in their coverage
(across months) and biologically biased (towards males) and as such results from our preliminary efforts should be
considered in light of these caveats. However, these preliminary results are valuable and indicate likely co-occurrence
with high density shipping traffic routes in the region and target additional areas for focussed field surveys. Results
from this study should be considered together with results of recent north Indian Ocean blue whale ENM studies to help
guide future research and conservation management objectives in the region.
Minton,G.,Collins,T.J.Q.,Findlay,K.P.,Baldwin,R,Ersts,P.J.,Rosenbaum,H.C.
Seasonal distribution and population characteristics of humpback whales in Oman Technical Report
no. 413, 2006, ISBN: SC/A06/HW48.
Abstract | BibTeX | Tags: Australia, cetacean, Distribution, habitat, habitat preference, habitat preferences, Humpback Whale, humpback whales, Oman, population, population characteristics, Southern Hemisphere, whale, whales
@techreport{,
title = {Seasonal distribution and population characteristics of humpback whales in Oman},
author = {Minton,G.,Collins,T.J.Q.,Findlay,K.P.,Baldwin,R,Ersts,P.J.,Rosenbaum,H.C.},
issn = {SC/A06/HW48},
year = {2006},
date = {2006-01-01},
journal = {Document presented to the Workshop on the Comprehensive Assessment of Southern Hemisphere Humpback Whales, Hobart, Australia, April 2006},
volume = {SC/A06/HW48},
number = {413},
pages = {1-48},
abstract = {Previously published data on the occurrence of humpback whales (Megaptera novaeangliae) in the Arabian Sea suggest that the region hosts a non-migratory population that adheres to a Northern Hemisphere breeding cycle. Twelve small boat surveys were conducted at three main locations off the coast of Oman between February 2000 and November 2004 to investigate the distribution and seasonal abundance of humpback whales and other cetaceans. An even ratio of males and females were observed and sampled during surveys in the Gulf of Masirah in October and November (n=38), while almost all whales sampled in Dhofar February/March were male (n=28). Song was detected frequently in the Kuria Muria Bay in February/March, but observations of mother-calf pairs were sparse, and competitive groups were absent. Feeding was observed in both October/November and February/March, but behavioural and environmental observations indicate that the Gulf of Masirah is primarily an important feeding ground, while the Dhofar region, particularly the Kuria Muria Bay, appears to be a breeding area. However, a lack of recent observations of both mother-calf pairs and competitive groups raises the possibility that the primary mating, calving and nursing areas are yet to be identified. Of the 64 whales that have been identified using photographs of dorsal fins or tail flukes, six individuals have been observed on at least two surveys, four individuals on three surveys, one on four surveys and one on five separate surveys. Individually identified whales were re-sighted in both the Gulf of Masirah and Dhofar at different times of the year and across survey years, indicating year-round residence off the coast of Oman. A Chapman's modified Petersen estimator was applied to various data pairings to calculate abundance in the areas surveyed. All pairings yielded estimates of less than 100 individuals, but sample sizes were small there are various sources of possible bias. Analysis of scarring on the caudal peduncle region of individually identified whales in Oman indicate that between 30 and 40% of identified whales are likely to have been involved in entanglements with fishing gear. Comparison of the Oman photo-identification catalogue with those from Zanzibar, Antongil Bay (Madagascar) and Mayotte and the Geyser Atoll (Comoros Archipelago), yielded no photographic matches, and support the hypothesis of a discrete population as did comparison of the distribution of fluke pigmentation rankings from the Oman catalogue, which varied significantly from those of Madagascar and Mayotte. In general the data examined in this study suggest that the population or sub-population of humpback whales off the coast of Oman is resident year-round, small and potentially discrete, warranting further research and conservation efforts.},
keywords = {Australia, cetacean, Distribution, habitat, habitat preference, habitat preferences, Humpback Whale, humpback whales, Oman, population, population characteristics, Southern Hemisphere, whale, whales},
pubstate = {published},
tppubtype = {techreport}
}
Previously published data on the occurrence of humpback whales (Megaptera novaeangliae) in the Arabian Sea suggest that the region hosts a non-migratory population that adheres to a Northern Hemisphere breeding cycle. Twelve small boat surveys were conducted at three main locations off the coast of Oman between February 2000 and November 2004 to investigate the distribution and seasonal abundance of humpback whales and other cetaceans. An even ratio of males and females were observed and sampled during surveys in the Gulf of Masirah in October and November (n=38), while almost all whales sampled in Dhofar February/March were male (n=28). Song was detected frequently in the Kuria Muria Bay in February/March, but observations of mother-calf pairs were sparse, and competitive groups were absent. Feeding was observed in both October/November and February/March, but behavioural and environmental observations indicate that the Gulf of Masirah is primarily an important feeding ground, while the Dhofar region, particularly the Kuria Muria Bay, appears to be a breeding area. However, a lack of recent observations of both mother-calf pairs and competitive groups raises the possibility that the primary mating, calving and nursing areas are yet to be identified. Of the 64 whales that have been identified using photographs of dorsal fins or tail flukes, six individuals have been observed on at least two surveys, four individuals on three surveys, one on four surveys and one on five separate surveys. Individually identified whales were re-sighted in both the Gulf of Masirah and Dhofar at different times of the year and across survey years, indicating year-round residence off the coast of Oman. A Chapman's modified Petersen estimator was applied to various data pairings to calculate abundance in the areas surveyed. All pairings yielded estimates of less than 100 individuals, but sample sizes were small there are various sources of possible bias. Analysis of scarring on the caudal peduncle region of individually identified whales in Oman indicate that between 30 and 40% of identified whales are likely to have been involved in entanglements with fishing gear. Comparison of the Oman photo-identification catalogue with those from Zanzibar, Antongil Bay (Madagascar) and Mayotte and the Geyser Atoll (Comoros Archipelago), yielded no photographic matches, and support the hypothesis of a discrete population as did comparison of the distribution of fluke pigmentation rankings from the Oman catalogue, which varied significantly from those of Madagascar and Mayotte. In general the data examined in this study suggest that the population or sub-population of humpback whales off the coast of Oman is resident year-round, small and potentially discrete, warranting further research and conservation efforts.
Ballance,L.T,Pitman,R.L.
Cetaceans of the Western Tropical Indian Ocean: Distribution, Relative Abundance, and comparisons with Cetacean Communities of Two other Tropical Ecosystems Journal Article
In: Marine Mammal Science, vol. 14, no. 321, pp. 429-459, 1998.
Abstract | BibTeX | Tags: abundance, cetacean, cetaceans, Distribution, dolphin, dolphins, Gulf of Mexico, habitat preference, Indian Ocean, Maldives, Mexico, Oman, relative abundance, seabirds, survey, whale
@article{,
title = {Cetaceans of the Western Tropical Indian Ocean: Distribution, Relative Abundance, and comparisons with Cetacean Communities of Two other Tropical Ecosystems},
author = {Ballance,L.T,Pitman,R.L.},
year = {1998},
date = {1998-01-01},
journal = {Marine Mammal Science},
volume = {14},
number = {321},
pages = {429-459},
abstract = {We conducted a cetacean survey in the pelagic western tropical Indian Ocean (WTIO) aboard an 85-m research vessel from March to July 1995, covering 9,784 linear km. Using 25x binoculars and line-transect methods, we recorded 589 sightings of 21 species. Stenella longirostris was the most abundant cetacean, in terms of number of individuals sighted, by an order of magnitude above any other species, while Physeter macrocephalus was the most frequently sighted, in terms of number of schools. Twelve species were widespread, seven were rare, and two were localized; our sightings include new distributional records for 12 species. Significant observations included the following: (1) Delphinus cf. tropicalis was abundant off the coast of Oman (16 sightings) and readily distinguishable in the field from D. delphis and D. capensis, (2) Balaenoptera musculus was fairly common and localized in the area of the Maldives (17 sightings), and (3) three sightings were made of an unidentified bottlenose whale tentatively referred to as Indopacetus (i.e., Mesoplodon) pacificus. We recorded 26 mixed-species cetacean schools, 43 schools with which seabirds associated, and 17 schools associated with tuna. Notable among these were mixed aggregations of Stenella attenuata, S. longirostris, yellowfin tuna, and seabirds. The cetacean community of the WTIO was similar to that of the eastern tropical Pacific (ETP) and the Gulf of Mexico (GM) in several respects. First, differences in abundance rank of individual species were small, with the result that common species were common and rare species were rare, regardless of ocean. Second, these differences in abundance were due primarily to differences in encounter rate, which varied with ocean by as much as 3,000%, and less so to school size, which generally varied less than 100%. Third, regardless of ocean, three species comprised the majority of cetaceans in the community, Stenella attenuata, S. longirostris, and S. coeruleoalba, representing 62%-82% of all individuals for all species. However, the rank order of abundance for these three species differed with ocean. Most notably, S. attenuata was abundant in the ETP and GM (abundance rank = 2 and 1, respectively) but much less common in the WTIO (abundance rank = 6). Although habitat preferences for S. attenuata appear to overlap considerably with those of S. longirostris in the ETP, our results suggest there may actually be significant differences between these two species. Detailed analysis of oceanographic correlates of distribution will be necessary in order to understand fully the habitat requirements of these pelagic dolphins, often the most conspicuous elements of tropical cetacean communities around the world.},
keywords = {abundance, cetacean, cetaceans, Distribution, dolphin, dolphins, Gulf of Mexico, habitat preference, Indian Ocean, Maldives, Mexico, Oman, relative abundance, seabirds, survey, whale},
pubstate = {published},
tppubtype = {article}
}
We conducted a cetacean survey in the pelagic western tropical Indian Ocean (WTIO) aboard an 85-m research vessel from March to July 1995, covering 9,784 linear km. Using 25x binoculars and line-transect methods, we recorded 589 sightings of 21 species. Stenella longirostris was the most abundant cetacean, in terms of number of individuals sighted, by an order of magnitude above any other species, while Physeter macrocephalus was the most frequently sighted, in terms of number of schools. Twelve species were widespread, seven were rare, and two were localized; our sightings include new distributional records for 12 species. Significant observations included the following: (1) Delphinus cf. tropicalis was abundant off the coast of Oman (16 sightings) and readily distinguishable in the field from D. delphis and D. capensis, (2) Balaenoptera musculus was fairly common and localized in the area of the Maldives (17 sightings), and (3) three sightings were made of an unidentified bottlenose whale tentatively referred to as Indopacetus (i.e., Mesoplodon) pacificus. We recorded 26 mixed-species cetacean schools, 43 schools with which seabirds associated, and 17 schools associated with tuna. Notable among these were mixed aggregations of Stenella attenuata, S. longirostris, yellowfin tuna, and seabirds. The cetacean community of the WTIO was similar to that of the eastern tropical Pacific (ETP) and the Gulf of Mexico (GM) in several respects. First, differences in abundance rank of individual species were small, with the result that common species were common and rare species were rare, regardless of ocean. Second, these differences in abundance were due primarily to differences in encounter rate, which varied with ocean by as much as 3,000%, and less so to school size, which generally varied less than 100%. Third, regardless of ocean, three species comprised the majority of cetaceans in the community, Stenella attenuata, S. longirostris, and S. coeruleoalba, representing 62%-82% of all individuals for all species. However, the rank order of abundance for these three species differed with ocean. Most notably, S. attenuata was abundant in the ETP and GM (abundance rank = 2 and 1, respectively) but much less common in the WTIO (abundance rank = 6). Although habitat preferences for S. attenuata appear to overlap considerably with those of S. longirostris in the ETP, our results suggest there may actually be significant differences between these two species. Detailed analysis of oceanographic correlates of distribution will be necessary in order to understand fully the habitat requirements of these pelagic dolphins, often the most conspicuous elements of tropical cetacean communities around the world.