Our directory of things of interest

University Directory

‘Gentle giants’ urgently need conservation management

  • Written by  Lucy Hodge-Sellers
  • Published in Wildlife
‘Gentle giants’ urgently need conservation management (Image: www.simonjpierce.com)
17 Aug
Whale sharks have been found to not travel far from familiar coastlines, putting them at risk from human activities

The largest living fish on Earth roams less than previously thought, a new study finds. Whale sharks are solitary creatures which have been previously difficult to monitor due to high individual mobility. However, research in the Indo-Pacific region, carried out by Dr Clare Prebble, Whale Shark Project researcher for the Marine Megafauna Foundation (MMF) has discovered that whale shark aggregations segregated by life stage and gender, experience minimal interactions between one another and limited movement across specific aggregation sites.

Prebble found that despite their high mobility many whale sharks, particularly juvenile males, are predominantly localised in specific coastal areas, as well as around islands in the tropics and subtropics. They have been observed targeting predictable feeding opportunities such as fish spawning events, but have shown low levels of movement between three major feeding sites in the Western Indian Ocean (Mozambique and Tanzania) and the Arabian Gulf (Qatar), where groups rarely swam more than a few hundred kilometres north or south from their established individual areas.

Whale Shark spot ID(Image: Wild Me. Wildbook for Whale Sharks - whaleshark.org)

The whale sharks were monitored by the MMF using various innovative methods of data collection, from ‘biological passports’ to photo identification. With photo IDs, the MMF used the natural markings on each animal to identify individuals. Each shark has a unique spot pattern, much like a human fingerprint, which is thought to remain unchanged throughout their life. A shark’s pattern is photographed and run through software on the Wild Book for Whale Sharks platform (www.whaleshark.org), a system that has been adapted from NASA software used to identify star constellations. This database compares each photograph to all the identified sharks in the world and informs the MMF which shark is which.

online article whale spots(Image: Wild Me. Wildbook for Whale Sharks - whaleshark.org)

However, the MMF’s newest data collection technique is the biochemical analysis of tissue biopsies, known as ‘stable isotope analysis’. This involves the production of ‘isoscapes’ – the mapping of isotopic gradients over a range of geographic scales. Isotopes vary spatially within ecosystems, with heavier variants found more in near-shore environments than offshore, and more at higher latitudes in the poles than at the equator. These isotopes are passed up through the food web to the tissues of consumers (such as the whale sharks).

‘Every time a whale shark eats something it is accumulating evidence of where and what it was eating, like putting a stamp in a passport,’ explains Dr Prebble. ‘When we look at the isotopic composition of their tissues, it’s like we’re leafing through their passport looking at what they’ve been doing the last few weeks or months.’

The whale shark is considered an endangered species by the International Union for the Conservation of Nature (IUCN) Red List. The Indo-Pacific whale shark population is thought to have shrunk by 63 per cent over the past 75 years, with more than half of the world’s population having been killed since the 1980s alone. Today, the world’s largest feeding areas only host a few hundred sharks at most.

onlinearticle shutterstock 185719748 2

As they are long-lived, slow-growing, and late to mature, whale sharks are particularly vulnerable to human threats. The WWF claims that ‘demand for their meat, fins and oil remains a threat to the species, particularly by unregulated fisheries. They are victims of by-catch, the accidental capture of non-target species in fishing gear. Whale shark tourism [worth over $100million each year worldwide] presents a threat to the species as it can interrupt their feeding and sharks can be injured by boat propellers.’

The incidental catching of whale sharks in gillnets results in an estimated 50 to 60 per cent of accidentally captured sharks being released alive and five to ten per cent dying. The fate of the remaining 30 to 40 per cent captured unfortunately remains unknown due to inaccurate reporting. The IUCN claims that ‘restrictions on mesh size, net length and fishing locations can help to avoid whale shark catch. Training in safe release, or provision of by-catch reduction technologies (deliberate weak points in nets or other ways to avoid entanglement) could help to reduce the likelihood of shark injury or mortality when interactions occur.’

onlinearticle shutterstock 685576858 2

With the MMF now understanding that many whale sharks are highly localised, with their worlds much more intertwined with our own than previously thought, it is urging conservation management techniques be established. ‘Our results show that we need to treat each site separately, and ensure good conservation management is in place, as the sharks may not re-populate if they’re impacted by people’s activities,’ Prebble claims. As a range of threats including potential future concerns such as climate change and increased marine pollution events occur, a lack of conservation could potentially lead to higher mortality, displacement from preferred habitats and the rising concern of extinction.

red line


Geographical Week

Get the best of Geographical delivered straight to your inbox by signing up to our free weekly newsletter!

red line

Related items

Geographical Week

Get the best of Geographical delivered straight to your inbox every Friday.


Subscribe to Geographical!

University of Winchester


Aberystwyth University University of Greenwich The University of Winchester




Travel the Unknown


Like longer reads? Try our in-depth dossiers that provide a comprehensive view of each topic

  • The Human Game – Tackling football’s ‘slave trade’
    Few would argue with football’s position as the world’s number one sport. But as Mark Rowe discovers, this global popularity is masking a sinister...
    Essential oil?
    Palm oil is omnipresent in global consumption. But in many circles it is considered the scourge of the natural world, for the deforestation and habita...
    Hung out to dry
    Wetlands are vital storehouses of biodiversity and important bulwarks against the effects of climate change, while also providing livelihoods for mill...
    The true cost of meat
    As one of the world’s biggest methane emitters, the meat industry has a lot more to concern itself with than merely dietary issues ...
    Mexico City: boom town
    Twenty years ago, Mexico City was considered the ultimate urban disaster. But, recent political and economic reforms have transformed it into a hub of...


NEVER MISS A STORY - Follow Geographical on Social

Want to stay up to date with breaking Geographical stories? Join the thousands following us on Twitter, Facebook and Instagram and stay informed about the world.

More articles in NATURE...


The demand for horseshoe crab blood – vital for testing…


One of the problems in getting accurate climate science out…


Italy is divided over the future of its wolves and…


A Scottish tidal power project in the Pentland Firth has…


The world’s first full global analysis of beaches reveals the…


With the recent Saddleworth Moor fire, it can be easy…


Whale sharks have been found to not travel far from…


The Lone Star tick is spreading across North America, carrying…


Earlier this week, Indonesia was struck by a series of…


Efforts to reduce the energy drain of the internet are…


Coal’s rising popularity among climate-apathetic leaders is a worrying trend,…


Sharing the ideas of climate justice with a little humour…


Rising bedrock under the West Antarctic Ice Sheet could prevent…


Officially declared the world’s ‘most overfished sea’, the Mediterranean is…


An interview with biologist Chris D Thomas, author of ‘Inheritors…


Some may see using the 50mm lens as a regressive…


With the war against plastic gaining publicity and popularity, one…


India’s booming domestic dog population is attacking some of the…


Soaring sales of air conditioning units over the next thirty…


Well-meaning promises and actions don't always have the best outcomes.…