Blue whales are fascinating animals. At 24-30 metres in size (longer than a basketball court docket) they’re the most important creatures on Earth. They’re additionally among the many rarest. Estimates counsel that there are solely round 5,000 to fifteen,000 blue whales left on the planet.
Their populations skilled a 89-97% decline attributable to industrial whaling actions worldwide that began within the North Atlantic in 1868. Blue whales had been primarily valued for his or her blubber, remodeled into oil and utilized in cosmetics and cleaning soap, for the lubrication of business gear, and as lamp oil. In 1978, the final deliberate seize of a blue whale was recorded off Spain.
In the present day, blue whales are present in all oceans besides the Arctic. They normally migrate from their summer season feeding grounds the place they nearly solely feed on krill to their winter breeding grounds. Nonetheless, their migration patterns are nonetheless poorly understood, significantly within the Indian Ocean, the place restricted analysis has been carried out.
Traditionally, the Seychelles archipelago – off the coast of east Africa – was an opportunistic whaling floor for Soviet whaling fleets en path to and from the Antarctic. Within the waters of the northern Indian Ocean, whalers illegally killed greater than 1,200 blue whales, together with 500 close to the Seychelles, between 1963 and 1966.
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Since then, no devoted analysis had occurred to evaluate the abundance of blue whales on this area till 2020, once I partnered with the College of Seychelles, Oceanic Movies (UK) and my colleague, Kate Stafford, to analyze.
We carried out two expeditions in November 2020 and 2021. After surveying about 5,500km throughout the northern Seychelles, we had a complete of 5 sightings of as much as 10 blue whales.
This was an outstanding discovering. We had been ready to not see any blue whales because of the excessive degree of looking that occurred pretty not too long ago and completely no info was accessible because the final blue whale was killed within the area in 1964.
When blue whales had been sighted, we approached them slowly to acquire particulars of their group dimension and behavior. Pictures of each left and proper sides of the dorsal area had been taken to establish them.
As a result of colouration patterns are distinctive to every animal, we knew that not less than 5 people had been recognized throughout this expedition.
After sharing our footage with different analysis teams engaged on blue whales within the Indian Ocean, no “match” was discovered. This implies the whales we recognized in Seychelles may need been photographed for the primary time ever!
Though blue whales are now not hunted and are protected by a number of worldwide conventions, they’re nonetheless listed as endangered on the IUCN (Worldwide Union for the Conservation of Nature) Purple Listing of Threatened Species. They face a spread of threats. As an illustration, transport site visitors causes noise air pollution that can alter communication and result in collisions. Local weather change can also be affecting the distribution and abundance of their key meals, krill.
Discovering the whales
The blue whale’s huge oceanic habitat and elusive nature make them extremely difficult to check. Furthermore, their deep dives and in depth migrations spanning hundreds of kilometres current logistical hurdles for researchers aiming to trace their actions and behavior.
Understanding their ecology, inhabitants dynamics and conservation due to this fact requires revolutionary and resource-intensive analysis strategies, reminiscent of systematic surveys from giant vessels or planes to evaluate their abundance or satellite tv for pc tagging to analyze their actions and migrations.
Our expeditions consisted of vessel-based visible surveys that targeted on the deep waters (500−2,000 metres) off the northern portion of the Mahé Plateau.
As well as, for over a 12 months, we positioned a hydrophone (an underwater microphone able to recording whale vocalisations) in an space the place blue whales had been prone to happen. This allowed us to substantiate that blue whales in Seychelles had been extra widespread than we thought however extremely seasonal (regardless that we recorded blue whale calls all year long), primarily from December to April.
This technique additionally revealed that our expeditions (in November of 2020 and 2021) didn’t happen when blue whales had been probably the most plentiful. It signifies that our future surveys must happen in the course of the months of March and April, when their abundance is at its peak.
Their songs matched these of blue whales recorded close to Sri Lanka (about 3,100km from Seychelles), within the central tropical Indian Ocean. The seasonality in Seychelles is much like the presence of blue whales in Sri Lanka, which can also be highest from December to April.
Jeremy J. Kiszka/Florida Worldwide College
After spending 5 weeks scanning the ocean, we recorded a complete of 23 species of whales and dolphins in 30 days of energetic search effort, which is exceptional.
We recorded over 100 sightings of Bryde’s whales (Balaenoptera edeni), a non-migrating whale species solely residing in tropical and subtropical waters, but in addition many sperm whales (Physeter macrocephalus) and beaked whales. The presence of all these species in Seychelles means that the atmosphere is productive sufficient to help giant portions of cetaceans. We’ll additional examine this sooner or later, significantly to make sure that these extraordinary animals, together with blue whales, persist in these waters.
Of the 4 subspecies of blue whale that we all know exist, three are recognized to be current within the Indian Ocean. We imagine that the pygmy blue whale is the subspecies visiting Seychelles, based mostly on the bodily traits of the animals we noticed and, most significantly, the character of their name.
The pygmy blue whale is mostly smaller than different subspecies. It usually reaches lengths of round 21-24 metres. Different blue whale subspecies, such because the Antarctic blue whale, can develop to 30 metres or extra. The pygmy blue whale is primarily discovered within the southern hemisphere and has acoustic traits which can be distinct from others, significantly Antarctic blue whales.
What’s subsequent?
Due to our blue whale discoveries, now we have engaged with native tourism operators and the federal government, significantly to establish measures to restrict the impression of the potential growth of whale watching as an exercise. These are constructive steps in direction of their conservation. The involvement of native college students on the College of Seychelles and younger researchers can also be vital for the long-term sustainability of analysis and conservation initiatives.
We nonetheless know so little about blue whales. However the knowledge collected in Seychelles offers us hope and encourages us to do extra.
We now want to extend our analysis efforts to evaluate the abundance of those blue whales in Seychelles and uncover why they’re utilizing Seychelles’ waters. Do they only breed or feed in these waters, or each?
We additionally need to acquire additional insights into what they eat and the way the altering local weather is affecting their distribution and behavior within the tropical waters of the Indian Ocean.
