Marine Life

Rare mako shark 'could survive catastrophe' with genetic lifeline

New research has found that species resilience gained through genetic diversity within the population of Atlantic shortfin mako sharks could be its best hope of surviving a catastrophic event such as climate change... if we can just stop overfishing them.

03/02/2025
Words by Rob Hutchins
Photography by Ron Watkins
Additional photography by Mark Conlin

The discovery of a diversity lifeline for the endangered shortfin mako shark could be its best chance for surviving a ‘catastrophic event’ such as climate change, but geneticists behind the revelation have warned it won’t mean anything if we fail to “urgently curb overfishing”.

With its reputation as the fastest shark in the sea, the shortfin mako is also among the world’s most endangered species. It currently holds an ‘Endangered’ status on the International Union for the Conservation of Nature’s Red List of Threatened Species, and has also found its place on Appendix II of the Convention on Trade in Endangered Species of Wild Fauna and Flora.

Overfishing is currently driving sharks to the edge of existence. Recent scientific assessments have shown that more than one-third of sharks, rays, and chimaeras are threatened with extinction from a host of pressures, including habitat loss and degradation, deep-sea mining, and pollution.

Researchers argue, however, that the greatest concern lies in the unsustainable global demand for the meat, fins, and other products from sharks. Today, two-thirds of all these threatened species of shark are at risk from overfishing alone.

But nature has thrown the shortfin mako a lifeline; a couple of lifelines to be more precise.

“There’s some good news here. Despite decades of heavy overfishing, shortfin mako sharks in the Atlantic Ocean still show relatively high levels of genetic diversity,” said Professor Mahmood Shivji, director of the Save Our Seas Foundation Shark Research Centre and Guy Harvey Research Institute, Nova Southern University. 

Genetic diversity is a lifeline for a species on the edge of extinction. Professor Shivij has explained that the greater the diversity in a population, the higher their ‘resilience’. What this means is that the more variation there is among a species, the better chances that species can adapt to changes or survive a catastrophe.

“What that means for shortfin mako sharks is that if we can prevent further erosion of this genetic diversity by urgently curbing overfishing, we have more hope for this species to retain the resilience needed for its populations to adapt to our fast-changing climate and survive,” Professor Shivij continued. “But shortfin mako sharks have to be a conservation priority.”

A large, wide-ranging ocean predator, the shortfin mako will typically encounter numerous fisheries across its range. As a result, the species has been fished – usually for its lucrative fins and meant – to critical levels. 

Recent reviews of the ecological role of sharks in our ocean ecosystem show that large predators tend to play an outsized role in how the ecosystems function. Some big sharks influence their prey’s behaviour, or that of their competitors. The shortfin, for instance, has evolved to outpace prey like tuna and other swift swimmers, such as swordfish and mackerel.

To date, there has been little data on the genetic status of the shortfin mako to guide the conservation and management efforts around it. Populations are currently managed as two presumed separate populations (or stocks), and assessments indicate that northern Atlantic mako sharks are indeed overfished. 

Independent scientific surveys using data from satellite tags deployed on shortfin mako sharks suggest, however, that fishing mortality may be as much as ten times higher than some estimates from previous fisheries models.

So, what about this genetic diversity?

In his paper, Connections across open water: A bo-organelle, genomics-scale assessment of the Atlantic-wide population dynamics in a pelagic, endangered apex predator shark published recently in Evolutionary Applications, Professor Shivij and his colleague, Dr Andrea Bernard acknowledge that as a wide-ranging, open-ocean shark, the shortfin mako mixes freely with few physical or genetic barriers.

Data compiled by the researchers suggests that both the male  and female shortfin mako sharks – which grow much larger than the males –  are ranging and reproductively spreading their genes across the Atlantic.

“But when we look at the mitochondrial DNA – the genetic material inherited only from mothers – we see a contrasting picture,” said Professor Shivij. 

In fact, the results from sequencing entire mitochondrial genomes from shortfin mako sharks across the Atlantic have shown that there is a distinct genetic structure for both the northern and southern hemisphere populations. 

“This is scientific-speak, telling us that the populations in each hemisphere differ and are genetically distinct from each other,” said Professor Shivij. “In fact, the results suggest that although female shortfin mako sharks may well be as wide-ranging as their male counterparts, they return to key sites in one hemisphere to pup.”

If we’re to protect this important genetic diversity, the paper has argued, the management of two distinct Atlantic populations – the northern Atlantic and southern Atlantic shortfin mako sharks – has to be considered.

“We were very surprised to see this result. Typically, in most of the species we study, we see pretty low diversity,” said Professor Shivij. 

The hammerhead shark, for instance, stands in contrast to these findings. A species being overfished to the edge of extinction, the hammerhead’s vulnerability is greater because “it lacks the diversity to adapt to our rapidly changing climate”, even if we were to combat overfishing. 

“Predicting how species will respond to rising temperatures and changing ocean chemistry is complex and under continuously evolving scientific scrutiny. The relatively high levels of genetic diversity still present in the shortfin mako shark provide optimism that this magnificent large ocean predator has a good chance to adapt and survive in our changing world – if the current overfishing of it comes to an end.”

Click here for more from the Oceanographic Newsroom. 

Words by Rob Hutchins
Photography by Ron Watkins
Additional photography by Mark Conlin

Printed editions

Current issue

Back issues

Enjoy so much more from Oceanographic Magazine by becoming a subscriber.
A range of subscription options are available.