Great white sharks separated into three distinct population groups up to 200,000 years ago and continue to mix only within these separate groups, new research has found.
Lead investigators in a global collaboration, scientists at the University of Aberdeen have applied cutting-edge novel genome analyses to white shark populations around the world for the first time, with their results published in the journal Current Biology.
They found that there are three distinct geographic lineages which seldom interbreed; a southern Pacific Ocean population (Indo-Pacific), a northern Pacific Ocean population and a population in the North Atlantic and Mediterranean.
The discovery means the global populations of white sharks are at greater risk of extinction than previously thought as each rely on a smaller number of the species, with individuals from one lineage unlikely to make up shortfalls in another.
The research at Aberdeen was led by Dr Catherine Jones in partnership with Nord University, the Oslo Sequencing Centre, Potsdam University, and with collaborators around the world, including the Guy Harvey Research Institute at NSU, Florida, the MedSharks project, Italy, and Oceans Research Institute, South Africa, enabling the collection of biopsies throughout much of the white shark’s range.
READ MORE: Scots university to lead UK's push for ‘near-unhackable’ quantum internet
Dr Jones said: “At the end of the Penultimate Ice Age – between 100,000 to 200,000 years ago – white shark populations appear to have divided into three discrete lineages which seldom interbreed.
“This separation can still be observed today as modern major ocean currents seem to act as boundaries of the areas occupied by each group.
“If all the white sharks belonged to a single large, integrated global population, it would not matter so much if they vanished from a specific area. But if white sharks comprise separate genetically distinct populations, such as in the Mediterranean, and this were lost, unique genetic diversity would also be lost.”
Researchers say understanding the distribution and health of these distinct groups is key to future protection of the species.
Professor of Aquatic Biosciences at Nord University in Norway, Les Noble, who also holds an honorary position at the University of Aberdeen added: “Successful conservation requires recognition of management units, but this has been unavailable for white sharks, which were suspected to exist as a single global population.”
“Although not widely appreciated man’s future is increasingly bound up with that of white sharks. As top predators they play a crucial role in maintaining the health and diversity of local marine ecosystems which are responsible for 20% of protein in our diet. In the last 50 years white shark abundance has almost halved, and it is recognized as critically endangered in Europe.
Galice Hoarau, Professor of Molecular Ecology at Nord University, says “The lack of interbreeding suggests offspring from cross lineage matings may not be viable. Should recent forecasts of changes in strength and direction of major ocean currents over the next 50 years be accurate, breakdown of these geographic boundaries between lineages may allow more unproductive matings, further endangering white shark populations and the diversity, health and productivity of ocean ecosystems.”
The researchers suggest conservation efforts are likely to become critical in the next 50 years.
Dr Jones said: “It has long been considered that sharks lost from one area would be compensated for with the movement and matings of sharks from other locations. Our findings suggest this is clearly unlikely and this, together with bycatch fishing, depletion of their food reserves, pollution, and poaching, could put this iconic apex predator in real danger of extinction.”
Why are you making commenting on The Herald only available to subscribers?
It should have been a safe space for informed debate, somewhere for readers to discuss issues around the biggest stories of the day, but all too often the below the line comments on most websites have become bogged down by off-topic discussions and abuse.
heraldscotland.com is tackling this problem by allowing only subscribers to comment.
We are doing this to improve the experience for our loyal readers and we believe it will reduce the ability of trolls and troublemakers, who occasionally find their way onto our site, to abuse our journalists and readers. We also hope it will help the comments section fulfil its promise as a part of Scotland's conversation with itself.
We are lucky at The Herald. We are read by an informed, educated readership who can add their knowledge and insights to our stories.
That is invaluable.
We are making the subscriber-only change to support our valued readers, who tell us they don't want the site cluttered up with irrelevant comments, untruths and abuse.
In the past, the journalist’s job was to collect and distribute information to the audience. Technology means that readers can shape a discussion. We look forward to hearing from you on heraldscotland.com
Comments & Moderation
Readers’ comments: You are personally liable for the content of any comments you upload to this website, so please act responsibly. We do not pre-moderate or monitor readers’ comments appearing on our websites, but we do post-moderate in response to complaints we receive or otherwise when a potential problem comes to our attention. You can make a complaint by using the ‘report this post’ link . We may then apply our discretion under the user terms to amend or delete comments.
Post moderation is undertaken full-time 9am-6pm on weekdays, and on a part-time basis outwith those hours.
Read the rules here