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SC/69A/CMP/07
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Resource ID
19962
Access
Open
Document Number
SC/69A/CMP/07
Full Title
Cetacean surveys in Oman November 2019- November 2022
Author
Gianna Minton, Andrew Willson, Fredrik Christiansen, Aida Al Jabri, Rabab Al Lawati, Ammar Al Aamri, Robert Baldwin, Tim Collins, Salvatore Cerchio, Maia Sarrouf Willson
Authors Summary
Continuing over 20 years of research efforts focusing on Endangered Arabian Sea humpback whales (ASHW) in Oman, four vessel-based surveys were conducted in two areas off the coast of Oman between November 2019 and November 2022. ASWH encounter rates varied significantly from no encounters over two weeks of surveys in March 2021, to 40 encounters during two weeks of survey effort in November 2021. Over the course of all four surveys 57 ASHW sightings were documented, comprising 38 unique individuals, all of which were photo-identified, and 30 of which were filmed by UAV to assess body condition. Re-sightings rates were high, with 29 of the 38 identified whales representing whales that were already present in the Oman humpback whale Photo-ID catalogue, including 9 individuals that were first identified in 2001 or 2002. The body condition of sampled ASHWs ranged from -0.08 to +0.51%, with a mean of 0.12 (SD=0.126). There was a significant difference in body condition between sexes, with females on average having a 16.1 percentage units higher body condition than males. Bryde’s whale encounter rates were inversely proportional to humpback whale encounter rates, and appeared to be correlated with warmer sea surface temperatures in the study area. Body condition was also opportunistically assessed for 12 Bryde’s whales, including five mother-calf pairs. Bryde’s whale body condition ranged from -0.13 to +0.17%, with a mean of 0.00 (SD=0.092). These findings reinforce the need for continued monitoring of both species of whales’ relative abundance, distribution and health in relation to changing oceanographic conditions in the Arabian Sea that are likely to impact their preferred prey and foraging strategies.
Publisher
IWC
Publication Year
2023
Abstract
Arabian Sea humpback whales (ASHW) comprise an Endangered sub-population that does not undertake seasonal migrations between low-latitude breeding grounds and high latitude feeding grounds. The population has been the subject of discussions at IWC Scientific Committee meetings since the late 1990s when the unique nature of the population was first revealed by scientists working on illegal Soviet whaling vessels. Continuing over 20 years of research efforts in Oman, four vessel-based surveys were conducted in two areas of documented humpback whale abundance off the coast of Oman between November 2019 and November 2022. ASWH encounter rates varied significantly from no encounters over two weeks of surveys in March 2021, to 40 encounters during two weeks of survey effort in November 2021. Over the course of all four surveys 57 ASHW sightings were documented, comprising 38 unique individuals, all of which were photo-identified, and 30 of which were filmed by UAV to assess body condition. Re-sightings rates were high, with 29 of the 38 identified whales representing whales that were already present in the Oman humpback whale Photo-ID catalogue, including 9 individuals that were first identified in 2001 or 2002. The body condition of sampled ASHWs ranged from -0.08 to +0.51%, with a mean of 0.12 (SD=0.126). There was a significant difference in body condition between sexes, with females on average having a 16.1 percentage units higher body condition than males. Bryde’s whale encounter rates were inversely proportional to humpback whale encounter rates, and appeared to be correlated with warmer sea surface temperatures in the study area. Body condition was also opportunistically assessed for 12 Bryde’s whales, including five mother-calf pairs. Bryde’s whale body condition ranged from -0.13 to +0.17%, with a mean of 0.00 (SD=0.092). These findings reinforce the need for continued monitoring of both species of whales’ relative abundance, distribution and health in relation to changing oceanographic conditions in the Arabian Sea that are likely to impact their preferred prey and foraging strategies.