Two new papers reveal important insights into whales in the Northern Indian Ocean

Last week two new papers were published revealing important information about feeding and parasites in blue whales off Sri Lanka and humpback whale song off the Goan coast of India.  Read the full abstracts of these papers below:

de Vos A, Faux CE, Marthick J, Dickinson J, Jarman SN. 2018. New Determination of Prey and Parasite Species for Northern Indian Ocean Blue Whales. Frontiers in Marine Science, 5.

Press release: A study on the diet of Northern Indian Ocean blue whales has just been published in the journal Frontiers in Marine Science. The study revealed that while globally blue whale populations feed predominantly on Euphausiidae (krill), Northern Indian Ocean blue whales feed predominantly on Sergestid shrimps. This demonstrates that blue whales can locate and feed on dense swarms of other types of prey when they occur. Within the Indian Ocean, sergestids are present in the top 300 m of the water column, which correlates with the deep scattering layer in the area. This need to dive deeper in search of prey likely explains the prevalence of fluke up diving amongst blue whales in Sri Lankan waters relative to other parts of the world.

This study also found the presence of Acanthocephalan parasites in the stomach and intestines of the Northern Indian Ocean blue whales. While these parasites have previously been recorded in other ocean basins, this is the first record for this region. This finding highlights the need for further studies on parasitic flora and long-term monitoring of health of these cetaceans for their proper management and conservation.

The lead author, Dr. Asha de Vos, founder of The Sri Lankan Blue Whale Project the flagship project of Oceanswell was particularly excited about the implications of this finding. She said, “These findings highlight the need to continue long-term research efforts, study and evaluate species within their habitat ranges, understand their behavioural adaptations, and tailor-make management and conservation decisions based on their needs”. Co-author Dr. Simon Jarman from Curtin University and CSIRO further added, “Analysis of DNA from environmental samples can generate a lot of new ecological knowledge. This is a nice example of the sorts of information we can uncover with molecular analyses.”    To learn more about this research please contact Dr. Asha de Vos; Founder, Oceanswell: asha@oceanswell.org

Shyam Kumar Madhusudhana, Bishwajit Chakraborty & G. Latha (2018):
Humpback whale singing activity off the Goan coast in the Eastern Arabian Sea, Bioacoustics, DOI: 10.1080/09524622.2018.1458248

This paper also discusses the relevance of this study in relation to the wider Arabian Sea humpback whale population:  “Formal collaborative studies in the Arabian Sea region are in their early stages. Cursory comparison of vocalizations from this study with those collected off Oman from the same year provides some indication of shared themes (2017 email exchanges between S Madhusudhana and researchers S Cerchio, AJ Willson and MS Willson studying humpback whales along the coast of Oman; unreferenced, personal communication); however, this requires further dedicated analysis. These preliminary findings concur with comparison of historical song samples between Hallaniyat Bay in Oman and Sri Lankan side of the Gulf of Mannar that were found to have ‘virtually the same content’ (Whitehead 1985). Understanding regional transmission of song patterns is considered as a gateway to evaluating the connectivity between humpback whales in the Arabian Sea, and considered a priority for conservation management measures (Minton et al. 2015). Further collaboration on evaluation of song structure between these data-sets is warranted.”
Watch this space for the next steps in this exciting story that started with the recording of humpback whale song on both sides of the Arabian Sea in the early 1980s!