Iran’s reporting network yields valuable records of Bryde’s whales

Bryde’s whales (Balaenoptera edeni) sighting

In recent news from the region, two baleen whales were spotted by fishermen; Mr. Meysam Sajadi Far and Amir Jamshidiat from Kangan, at two different locations in the Persian* Gulf on the 20th and 21st of June 2023. The fishermen shared photos and videos of the sightings with ASWN members, Plan4theLand, who, in turn, shared photos with ASWN members with particular expertise in identifying baleen whales. It was agreed that the whales are very likely to be Bryde’s whales (Balaenoptera edeni) based upon some discernible features and elimination of other candidate species.

Caption: Locations of two Bryde’s whale sightings reported by fishers to ASWN Partners in Iran, Plan4theLand.

Sightings of Bryde’s whales are fairly common throughout the Northern Indian Ocean, including in the Persian* Gulf. ASWN members have reported many sightings over the years, and the ASWN Google Group email list has proven a good forum for sharing these sightings and confirming species’ identifications. The region hosts two 2 genetically recognized, but poorly studied subspecies of Bryde’s whale: the larger, offshore form, Balaenoptera edeni brydei, and the smaller, coastal form, Balaenoptera edeni edeni (Kershaw et al. 2013). Furthermore, researchers are always on the lookout for the more rarely documented Omura’s whale (Balaenotera omura) (Cerchio et al. 2019), which is similar in general size and warm-water range, and is known to occur in the region, based on a confirmed stranding record from Qeshm, Iran (Ranjbar et al. 2016). In the recent observations of these two baleen whales, photographic evidence clearly indicates that they are not Omura’s whales, leaving Bryde’s whale as the most likely alternative since other small to medium size balaenopterid (rorquals) whales are absent from the Gulf.

Reports from fishing communities and recreational vessels or other ‘citizen scientists’ are very helpful in learning more about the distribution of these whales in the region. This information plays a vital role in regional research and conservation efforts. During the 2023 IWC Scientific Committee meeting, the Committee discussed the importance of further investigations to better understand the drivers of the distribution and relative abundance of Bryde’s whales in the Arabian region.

Recent acoustic data from southern oman (Cerchio et al. 2023) indicated the consistent presence throughout the year of a vocalisation likely to be from Bryde’s whale, and the results of boat-based surveys (Minton et al. 2023) reflected an inverse relationship between detections of Bryde’s whales and humpback whales, with authors speculating that both species’ relative abundance may vary in relation to oceanographic conditions that favour one type of prey over another. There were several recommendations to continue this work and, when possible, combine observational and acoustic datasets within the Arabian Sea to advance our understanding of whale habitat use and distribution in the region. The sub-committee recommended regional collaboration to continue to collect information, and to conduct more dedicated research to better address the status of this species. The ASWN hopes to foster this regional collaboration and to support members in their efforts to foster effective reporting networks that will facilitate the contribution of more valuable sightings like this most recent one from Iran.

Cited Literature

  • Cerchio, S., Willson, A., Cholewiak, D., Sackett, M., Al Harthi, S., Baldwin, R., Collins, T., Minton, G., Sarrouf Willson, M., 2023. Acoustic monitoring for baleen whale vocalizations off southern Oman, 2020 to 2022. Document presented to the Scientific Committee of the International Whaling Commission SC/69A/CMP/12/Rev1, 18.
  • Cerchio S, Yamada TK and Brownell RL Jr (2019) Global Distribution of Omura’s Whales (Balaenoptera omurai) and Assessment of Range-Wide Threats. Front. Mar. Sci. 6:67. doi: 10.3389/fmars.2019.00067
  • Kershaw, F., Leslie, M.S., Collins, T., Mansur, R.M., Smith, B.D., Minton, G., Baldwin, R., LeDuc, R.G., Anderson, R.C., Brownell, R.L., 2013. Population differentiation of 2 forms of Bryde’s Whales in the Indian and Pacific Oceans. Journal of Heredity 104, 755-764.
  • Minton, G., Willson, A., Christiansen, F., Al Jabri, A., Al Lawati, R., Al Aamri, A., Baldwin, R., Collins, T., Cerchio, S., Willson, M.S., 2023. Cetacean surveys in Oman November 2019- November 2022. Docment presented to the Scientific Committee of the International Whaling Commission SC/69A/CMP/07, 19.
  • Ranjbar, S., Dakhteh, S. M. H., and Van Waerebeek, K. (2016). Omura’s whale Balaenoptera omurai stranding on Qeshm Island, Iran, Persian Gulf: further evidence for a wide (sub)tropical distribution. J. Mar. Biol. Oceanogr. 5:3. doi: 10.4172/2324-8661.1000161
*also known as the Arabian Gulf in many ASHW range countries
Lake Bled, Slovenia

Arabian Sea Whales at the 2023 IWC Scientific Committee Meeting

This year the annual IWC Scientific Committee (SC) meeting was held in Bled, Slovenia between the 24th April and the 6th May 2023. A few ASWN members had the opportunity to attend the meeting in person or virtually, including Gianna Minton, Andrew Willson, Sal Cerchio, Tim Collins, Aida al Jabri and Moazzam Khan. 

Arabian Sea Humpback Whales (ASHW) were identified as a priority candidate for a Conservation Management Plan (CMP) in 2010. During this year’s meeting the IWC SC congratulated  the significant progress that has been made towards the development of a joint CMS-IWC CMP for ASHWs despite the current obstacles. The efforts of Arabian Sea Whale Network members were acknowledged by the Committee members as essential to creating the framework to develop a CMP. The Committee commended stakeholders in Oman for hosting a workshop focusing on Conservation Management of  ASHW at national and regional levels, and further reiterated the importance of regional collaboration. 

A number of documents and papers were presented by ASWN members at the meeting including the following: 

  • The annual ASWN Progress Report (SC/69A/CMP/04Rev1): featured contributions from several ASWN members, including updates on both regional-level activities and  projects, sightings and stranding reports, and capacity building conducted at local and national levels throughout the region. The report highlighted the lack of  sightings of ASHWs in the Arabian Gulf in past years despite the increased observation and reporting efforts. The sub-committee on CMS encouraged both, the work of the ASWN, and continued progress towards developing and implementing a regional CMP.
  • Cetacean Surveys in Oman (SC/69A/CMP/07): Findings surveys conducted between November 2019 and November 2022 further reinforced the need for continued monitoring of species of whales’ relative abundance, distribution and health in relation to changing oceanographic conditions in the Arabian Sea.
  • Sightings of whales in the Northern Arabian Sea along the coast of Pakistan in 2022 and 2023 (SC/69A /CMP/05): reports on the past year’s results of  the WWF Pakistan crew-based observer programme, which still includes some humpback whale sightings despite a lack of funding for the captains that share sightings data.
  • Variation in songs of Arabian Sea humpback whales (SC/69A/CMP/10): indicates continued isolation of ASHW from other Indian Ocean humpback whale populations, a slow rate of song change in the Arabian Sea, and connectivity between Oman and India.
  • Acoustic monitoring for baleen whale vocalizations off southern Oman from 2020 to 2022 (SC/69A/CMP/12): reported frequent detections of blue whale songs from NWIO and CIO populations; indicating the two populations’ range overlap in southern Oman.
  • Geospatial analysis of ASHW habitat preference and ship strike risk assessment (SC/69A/HIM/07): presented a ship strike risk analysis and a suggestion  that routing vessels 40 nm further offshore from the current shipping lane off the Arabian Sea coast of Oman would reduce ship trike risk by as much as 88%.
  • A note on humpback whales (Megaptera novaeangliae) in the central Indian Ocean (SC/69A/ForInfo/33): described a bimodal pattern of occurrence of humpback whales in the CIO using information collated from various sources, including social media and a citizen science project.
  • Arabian Sea Humpback Whale (Megaptera novaeangliae) Singing Activity off Netrani Island, India (SC/69A/ForInfo/52 ): describes humpback whale song recorded by a passive acoustic recorder moored off of southern India.
  • Remote and non-invasive quantification of ‘Tattoo Skin Disease-Like’ dermatopathy in endangered Arabian Sea humpback whales using drone photography (SC/69A/ForInfo/68): Drone aerial photography was used as a complementary approach to images obtained during boat-based surveys to identify and quantify TSD-L lesions.
  • A report from the ASHW Biotelemetry ICG (SC/69A/SMP26):  described discussions related to the risks and potential value of continuing satellite tagging to address the key data gaps following previous tagging  studies.  The document includes recommendations to adopt rigorous tagging protocols following best practices that were endorsed by the committee. 

Actions recommended for the ASW by the Scientific Committee at IWC-SC Meeting 2023

Discussion of the body of work presented led the IWC Scientific Committee to draw the following conclusions and recommendations:

Excerpt from  Annex F ,  page 18-19 – recommendations for Arabian Sea humpback whales

The sub-committee applauded the stakeholder engagement workshop held in Oman to advance ASHW conservation and the potential benefits of a CMP. 

Noting that a) in 2008 the population of ASHW was estimated at 82 individuals, and that since then SC has repeatedly expressed concern about the urgent need for conservation management interventions; b) detection of ASHW song during the breeding season declined from 59% of monitored hours in 2011-12 to 2% in the 2021/2022 season, and that sightings of ASHW in formerly core habitat have become sporadic, coinciding with sea surface temperature anomalies which are at or above an upper threshold for ASHW; c) a weakening of the northwest Indian Ocean monsoon is causing deoxygenation and denitrification of surface waters, which is negatively influencing ecosystem productivity including sardines, an important ASHW prey; d) a 35% regional increase in the volume of vessel traffic between 2008 and 2018 has increased the risk of ship strike within ASHW core habitat; and e) two thirds of animals observed in the western Arabian Sea have scarring associated with fisheries interactions:

The committee commended efforts fostered by authorities to study the ASHW population and expressed deep concern for the population based on its current status and the degrading condition of its habitat, strongly reiterated that the Arabian Sea humpback whales are priority candidates for a CMP, and welcomed efforts to encourage range states to develop a joint CMS-IWC CMP. The sub-committee strongly recommended the following actions as a matter of absolute urgency throughout the ASHW range:

  1. produce a synthesis of ASHW distribution, identification of important habitats and potential threats throughout its range, and use these to develop marine spatial management plans across the region to mitigate impacts in high-risk areas with a focus on both commercial and artisanal fisheries interactions, and impacts from commercial shipping and ship strike risk assessments using multi-species and dynamic species distribution modelling approaches;
  2. support the continuation of the crew-based observer programme in Pakistan (SC/69A/CMP/05), and, where possible, replicate this approach throughout the region especially in areas where systematic cetacean surveys are not feasible;
  3. continue the use of UAVs to assess body condition in conjunction with other metrics to assess seasonal and annual variation and to evaluate health, scarring, and foraging success and that photographic data collected in Oman from 2019-2022 is used to conduct an updated visual health assessment using the same methodology as used by Minton et al. (2022);
  4. conduct continuous and simultaneous passive acoustic monitoring in ASHW identified habitat in both the western Arabian Sea (different parts of Oman’s waters, Socotra and the Gulf of Aden) and eastern Arabian Sea (Pakistan, India, Sri Lanka and the Maldives) to: (a) describe and assess changes in spatiotemporal distribution throughout the Arabian Sea and (b) use song structure variation as an indicator of movements of individuals, potential sub-structure within the population, and monitor for future mixing with other populations;
  5. conduct further satellite telemetry studies specifically aimed at filling important data gaps in the temporal distribution and sex composition of existing data, including assessing movement behaviour of individuals during the periods February and June to October, and increasing the sample size of females;
  6. collate and analyse stranding data throughout the suspected ASHW range to better understand trends in whale distribution and mortality;
  7. complete genetic analyses of the Megaptera indica type specimen in comparison with genetic samples from Oman in order to clarify the taxonomic status of ASHW; and
  8. regularly update abundance and trend estimates with the most recently available photographic mark-recapture data.

Furthermore, the subcommittee noted that the lack of funding for dedicated coordination of the network was potentially hindering progress toward a CMP, and recommended that funding be sought to support coordination and capacity building opportunities for a range country scientist to take on this role.  The subcommittee also discussed stranding records of Bryde’s whales from Pakistan and UAE. Given the limited information on Bryde’s whales in the region the committee recommended regional collaboration to conduct more dedicated research to better address the status of the species across the region. 

The complete report of the 2023 IWC-SC Meeting can be found here.