Minton,G.,Collins,T.J.Q.,Findlay,K.P.,Baldwin,R.,Rosenbaum,H.C.,Kennedy,F.D.,Cockcroft,V.
Preliminary investigations of humpback whale Technical Report
no. 414, 2002, ISBN: SC/54/H3.
Abstract | BibTeX | Tags: abundance, Arabian Sea, Distribution, habitat use, Humpback Whale, humpback whales, megaptera novaeangliae, Northern Hemisphere, occurrence, Oman, population, relative abundance, sex-ratio, song, survey, whale, whales, whaling
@techreport{,
title = {Preliminary investigations of humpback whale },
author = {Minton,G.,Collins,T.J.Q.,Findlay,K.P.,Baldwin,R.,Rosenbaum,H.C.,Kennedy,F.D.,Cockcroft,V.},
issn = {SC/54/H3},
year = {2002},
date = {2002-01-01},
journal = {Document presented to the 54th meeting of the International Whaling Commission},
volume = {SC/54/H3},
number = {414},
pages = {1-19},
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. Six small boat surveys and one shore-based survey were conducted at three locations off the coast of Oman between February 2000 and February 2002. Encounter rates varied between surveys from 0.0 whales/hour to 0.545 whales per hour. Two of 36 photo-identified whales were re-sighted between surveys. Sex ratios in October were near parity while all whales sampled in February were male. Song was detected frequently in the Kuria Muria Bay in February, but records of mother-calf pairs are sparse and competitive groups were absent. Feeding was infrequently observed in both October and February. Implications for relative abundance and habitat use are discussed. Additional questions are raised and recommendations for further research are made.},
keywords = {abundance, Arabian Sea, Distribution, habitat use, Humpback Whale, humpback whales, megaptera novaeangliae, Northern Hemisphere, occurrence, Oman, population, relative abundance, sex-ratio, song, survey, whale, whales, whaling},
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. Six small boat surveys and one shore-based survey were conducted at three locations off the coast of Oman between February 2000 and February 2002. Encounter rates varied between surveys from 0.0 whales/hour to 0.545 whales per hour. Two of 36 photo-identified whales were re-sighted between surveys. Sex ratios in October were near parity while all whales sampled in February were male. Song was detected frequently in the Kuria Muria Bay in February, but records of mother-calf pairs are sparse and competitive groups were absent. Feeding was infrequently observed in both October and February. Implications for relative abundance and habitat use are discussed. Additional questions are raised and recommendations for further research are made.
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.