13-06-2025
From Gansbaai to Indonesia: The astonishing 38,000km+ voyage of a misidentified white shark
This shark tale almost sank through the mesh of history into the murky deep but through sheer happenstance it improbably surfaced from the depths and into the light of scientific discovery.
In November 2016, a female white shark that had been satellite tagged off the Western Cape coastal town of Gansbaai in May 2012 was caught and killed by longline fishermen in Indonesian waters — but it would take years for the shark's fate to emerge.
The shark, named Alicia, has travelled an astonishing 38,000km by the time her satellite tag stopped emitting 1,000km southeast of Madagascar, according to scientists who have reported their findings in a soon to be published article in the peer-reviewed journal Wildlife Research.
Alicia from there made her way to Indonesia — the longest recorded migration of the species and the first time that a white shark from South African waters turned up in South East Asia.
'This report marks only the second recorded transoceanic dispersal event for the species from South Africa, highlighting that despite extensive research, much remains to be learned about white sharks' dispersal patterns in the southern hemisphere,' the authors write.
'The movement between southern Africa and Southeast Asia surpasses the 11,000km dispersal recorded for another sub-adult female white shark (named Nicole) from Gansbaai, South Africa, to the west coast of Australia.'
A happenstance of history
And this shark tale almost sank through the mesh of history into the murky deep, but through sheer happenstance it improbably surfaced from the depths and into the light of scientific discovery.
The shark's first transmission via satellite from its tag was recorded on 5 June 2012 in South African waters. Its last was sent 22 months later, in April 2014, 1,000km southeast of Madagascar.
After that there was radio silence, the shark's fate unknown as it travelled further through Neptune's realm.
And then, it turned out that Indonesian fishers had the tag as it had been extracted from the shark after it was caught in 2016 on a longline — and they rose to the monetary chum thrown out by an NGO called Project Hiu.
'Project Hiu works with local fishers in Indonesia to conserve sharks and has recently begun deploying satellite tags and offering a monetary reward for observing or recovering any shark tag… The fishers kept the tag and contacted Project Hiu members after learning about the monetary reward,' the scientists report.
The fishers netted an undisclosed amount of cash while researchers reeled in scientific gold.
Project Hiu contacted a company called Wildlife Computers with the serial number. Wildlife Computers provides advanced wildlife telemetry services such as tagging devices — and it had this tag in its database.
'Remarkably, the tag was identified as having been attached to a 390cm TL sub-adult female white shark in May 2012 in South Africa. Through subsequent investigations, including email correspondence and interviews with the fishers, we have determined that in November 2016, a 473cm TL female shark (misidentified at the time as a longfin mako shark) was captured in longline gear off the coast of Indonesia, Southeast Asia,' the authors write.
Scientific advancement and red flags
This astonishingly improbable sequence of events has enriched the scientific knowledge of the species while raising red flags about the misidentification of sharks caught and harvested by the commercial fishing industry in that region and more widely.
'Our shark was misidentified as a longfin mako. Fisheries records indicate about 30 of these are caught and landed in the area each year, and some level of misidentification is thought to be present in these records,' lead author Dylan Irion, an ecologist and PHD candidate at UCT, told Daily Maverick.
'What's worth noting is that the identification guidebook used by enumerators does not include a key for the white shark. It's also notable that this shark was gut-hooked.'
'Gut-hooked' effectively rules out catch and release.
The bottom line is that much of the data in this regard may be unreliable, and catches and mortality of white sharks and other endangered sharks may be much higher than the numbers suggest.
This meandering trip to Indonesia also throws into stunning relief the sheer stamina and adaptability of white sharks. This is a species that can travel bloody far, and it is not fussy about the hoods it moves through.
'In 2013, following a brief window of no satellite transmissions, the shark transmitted a location from inside the uThukela Banks Marine Protected Area located between the cities of Durban and Richards Bay along the South African coast, marking the start of a journey covering about 38,000km over 395 days, transmitting with a mean period of 8.55 hours between transmissions,' the authors write.
'During this time, she encountered a wide range of sea surface temperatures, ranging from 3.8 to 29°C, swam at an average speed of 56km per day and covered a cumulative distance of 37,178km, measured as the straight-line distance between satellite transmissions.'
That fittingly is the equivalent of swimming the distance of the Two Oceans Marathon every day.
'What continues to amaze me is how remarkably adaptable these sharks are, capable of thriving in an incredible range of environments, from the cold kelp forests of the Cape, sub-polar waters of sub-Antarctic, to the warm coral reefs of Indonesia,' Dr Alison Kock, a marine biologist and renowned shark expert at SANParks who was one of the co-authors of the paper, told Daily Maverick.
Mysteries of the deep
This long marine trek also comes against the backdrop of debates about why white sharks have seemingly vanished from previous hotspots for the species, such as Gansbaai.
Research by Kock and other scientists strongly suggests the species has moved eastward to escape the unwanted attention of a pair of orcas who have been preying on white sharks for their nutrient-rich livers.
Other scientists maintain the populations off Gansbaai and other Cape locations were in decline before the liver-loving orcas rocked up, with the commercial fishing industry seen as a prime culprit despite the white sharks' protected status.
The drum lines deployed by KZN Sharks Board's bather safety programme is also reaping a toll. A white shark tagged in Mossel Bay in May was recently killed in a drum line off the coast of Margate.
This correspondent has previously highlighted the jarring fact that when a US video crew came to South Africa in 1969 with the goal of filming white sharks from cages it went straight to Durban to follow commercial whaling vessels.
The crew did not even consider the Cape waters, which get only a brief but tantalising mention in the classic book about the expedition by Peter Matthiessen entitled Blue Meridian: The Search for the Great White Shark.
This suggests that white sharks over five decades ago may not have been abundant in the cold Cape waters. South Africa's white sharks appear for a range of factors to come and go — and when they go, they can clearly go far. DM
