Melissa Márquez
‘Swimming with whale sharks’ is on the bucket list of most people, but Brad Norman does it for a living. “I look forward to every time I have a chance to swim with the big fish,” says Norman, who is also CEO of the not-for-profit Ecocean.
It’s something he’s done thousands of times, but he still remembers the day he swum with one of Ningaloo’s most famous of these individuals, Stumpy. “I still remember the day I swam [with him] more than two decades ago. The exhilaration of seeing a creature the size of a bus emerging from the blue and swimming straight at me will never be forgotten.”
A circumglobal species, the whale shark (Rhincodon typus) lives in tropical and warm temperate oceans. The species is famous for migrating over thousands of kilometres, yet also resides year-round in certain regions, such as off the Indian Ocean coast of Tanzania in Africa. Despite being a solitary species, whale sharks are known to form seasonal, predictable aggregations at more than 20 sites worldwide, usually during periods of high productivity.
One of these sites is in Western Australia.
Every year, more than 200 types of coral spawn on the world heritage–listed Ningaloo Reef (“Nyinggulu”), luring the mysterious whale shark to Australian waters from March to July. Visitors from all over the world flock to snorkel with these gentle giants. Half-day and full-day eco-tours of whale shark swims are offered at both Exmouth and Coral Bay during these months, with the season often stretching through September or even October nowadays. These tourists clamour for photos of these gentle giants, and they even participate in photo-ID programs to help researchers learn more about them. This citizen science-derived data has been used to develop mark-recapture models, determine residency, annual abundance, and even evaluate long-term philanthropy.
And it all started because Norman looked up.
Instead of the model being used to study stars in the sky, it now studied the constellations which call the ocean home.
“I’d been working on whale shark photoidentification since 1995 and was able to prove that the pattern of spots on the skin of each shark was unique to each individual, and that photos could be used to monitor the species,” says Norman. “I started collecting hundreds of images but matching these by eye became challenging.” Based on the knowledge that whale shark’s skin pattern resembles stars in the night sky, and that NASA Hubble Space Telescope scientists map stars using a pattern-matching algorithm, Norman adapted the algorithm with the help of NASA astrophysicist Zaven Arzoumanian and information architect Jason Holmberg.
Instead of the model being used to study stars in the sky, it now studied the constellations which call the ocean home. “Together with scarring and other markers, spot patterns captured in photographs of whale shark flanks have been used, in the past, to make identifications by eye. We have automated this process by adapting a computer algorithm originally developed in astronomy for the comparison of star patterns in images of the night sky.” By integrating this software into the Shark Book website, any person who took a picture of a whale shark would be contributing to experts’ knowledge about these species worldwide – and help monitor their local populations.
This endangered species, however, only spends a short time in the protected waters of the World Heritage site. In order to conserve and manage mobile marine species, such as whale sharks, it is essential to understand how movement behaviour and space-use varies across individuals and populations.
Outside of the protected areas, Norman relies on satellites to ‘photograph’ whale sharks through the tags scientists attach to their dorsal fins. What comes out is not a photograph of the individual itself but of its movements. In the sky, these satellites are monitoring every data point – and what they’ve captured is concerning.
Globally, marine traffic has increased due to over 80% of international trade being carried by sea. This results in collisions with endangered megafauna on these ‘marine highways’ that cut through migratory routes of marine animals and have largely gone undetected or unreported until now. A combination of satellite-tracked movements of whale sharks and vessel activity indicates that 92% of sharks’ horizontal space use and nearly 50% of their vertical space use overlaps with persistent traffic from large vessels (>300 gross tons). “Even after accounting for the random technical failures of transmitters, we found 24% of tags stopped transmitting in busy shipping lanes, most likely due to whale sharks being lethally struck and sinking to the ocean floor,” the authors clarify.
The International Union for Conservation of Nature (IUCN) Red List of Threatened Species upgraded whale sharks from vulnerable to endangered, as a 50% decrease in whale shark populations has been documented over the past 75 years, according to research. While it has been thought that industrial fishing fleets aren’t a major cause of whale shark decline, this study shows that is not the case.
“Rapid industrialisation is definitely a cause of impact to whale shark populations. They get caught in fishing nets, get hit by ships, and are at risk of ingesting microplastics and other pollutants which clog their gills,” says Chloe Winn, a field assistant of the Maldives Whale Shark Research Programme.
And while many would think that whale sharks are safe within marine parks, like Shark Bay, Norman has also recently uncovered that over 18% of marine parks had extreme shipping exposure (an excess of 365 vessels per year). “Around all of Australia, 39% of satellite-tag reports from whale shark satellite-tag reports were in moderate shipping-exposure areas (>90 ships per year),” explains the research report.
The satellite-linked tags have also shown that whale sharks throughout the Indian Ocean vary in their exposure to anthropogenic impacts known to threaten this endangered species such as shipping or illegal fishing; the findings of his study emphasize the need for whale shark conservation efforts to be tailored to specific aggregations in order to mitigate regional threats to the species. Norman and his co-authors stress that the implementation of these efforts beyond national jurisdictions and addressing global conservation issues, such as the consequences of climate change and human population growth, requires multinational coordination.
The protection of these animals can be facilitated by multinational efforts, as well as by the simple interaction between a shark and a person.
The protection of these animals can be facilitated by multinational efforts, as well as by the simple interaction between a shark and a person. A tourist’s simple snap of their camera and uploading to the Shark Book website can become the photo that changes everything for researchers – and for these creatures. Or, as Brad Norman has done, following your dreams can even lead you to becoming a whale shark researcher! The relationship between whale sharks and researchers here is special, having developed a symbiotic relationship where they exchange parasite removal for research data. “As it turns out the whale sharks actually don’t mind the procedure at all,” University of Western Australia adjunct senior research fellow Dr Mark Meekan laughs. “In fact, some of them even slow down and stop and will actually let me get up the front of them and scrape lots of parasites off. I think that whale sharks probably look at me and go ‘what on earth is that inelegant, poorly swimming thing’, and when I start scraping the copepods off the lips, like, ‘oh my god, it’s the biggest cleaner fish I’ve ever seen’.”
If you would like to visit the whale sharks of Ningaloo, the Department of Biodiversity, Conservation and Attractions has published a guideline on best standard practices for how to interact with them. And to learn about the latest whale shark research done in the area, tune into the new ABC documentary series ‘Ningaloo Nyinggulu.’
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The Ultramarine project – focussing on research and innovation in our marine environments – is supported by Minderoo Foundation.