A series of recent shark attacks along Australia’s coastline has heightened public concern and renewed scientific scrutiny of a long-term rise in shark bite incidents, even as researchers caution that no single factor can fully explain the trend.

The latest incident occurred off Sydney when 34-year-old Leah Stewart suffered severe injuries from a suspected great white shark attack while swimming at a patrolled beach. Stewart was in clear water, between safety flags and during daylight hours, circumstances generally regarded by experts as reducing the likelihood of a shark encounter. She remains in critical condition after undergoing the amputation of one arm.

The attack has intensified anxiety among swimmers, surfers and beachgoers in Australia’s largest city. Sydney’s beaches have experienced several shark-related incidents in recent months, prompting some regular ocean users to reconsider entering the water.

Among them is Rob Harcourt, an emeritus professor at Macquarie University and head of its marine predator research group. A long-time surfer and swimmer, Harcourt says the recent incidents have had a noticeable psychological impact on coastal communities.

According to Harcourt, many experienced surfers have become reluctant to enter the water following the attacks. He describes a sense of unease that extends beyond those directly affected, reflecting broader fears about changing conditions in Australia’s coastal waters.

Australia ranks second globally behind the United States in the number of shark bites involving humans. However, while global trends have remained relatively stable, Australian data indicate a sustained increase in incidents over recent decades.

Researchers point out that Australia’s major population centers overlap with the habitats of three shark species most commonly associated with serious attacks: the great white shark, tiger shark and bull shark.

Data compiled through the Australian Shark Incident File show that during the 1950s, the country recorded an average of approximately 3.1 unprovoked shark incidents each year. These incidents include bites and attempted bites but exclude encounters involving provocation or activities such as spearfishing.

The number of incidents increased gradually over subsequent decades before accelerating in the early 2000s. During that period, annual incidents averaged around 12. In the current decade, the figure has risen to approximately 21 incidents per year.

Fatalities have also increased. Records indicate that shark-related deaths averaged about 1.7 annually during the 1950s. That figure has risen to approximately 3.8 deaths per year so far during the 2020s.

Experts note that improvements in emergency response capabilities may have prevented an even larger increase in fatalities. Faster medical intervention, enhanced rescue services and the widespread availability of tourniquet kits at surf lifesaving clubs have improved survival prospects for victims suffering traumatic injuries.

Interpreting the rise in incidents remains challenging. Population growth alone does not provide a complete explanation because available statistics do not account for how many people enter the water, how frequently they do so or whether they participate in activities that increase exposure to shark habitats.

Researchers have examined numerous possible contributing factors. A review of shark bite studies identified approximately 40 variables that have been proposed as influencing risk. These range from the growing popularity of surfing and other board sports to environmental factors such as proximity to river mouths and coastal ecosystem changes.

Despite these theories, scientists acknowledge that many proposed explanations remain insufficiently studied. Comprehensive research examining the relative importance of individual factors remains limited.

One area attracting increasing attention is the effect of ocean warming. Scientists say rising sea temperatures are altering marine ecosystems and influencing the distribution and behavior of numerous species, including sharks.

Warmer waters may encourage some shark species to spend longer periods in coastal areas where human populations are concentrated. This could increase the likelihood of encounters between sharks and people without necessarily indicating a substantial increase in shark numbers.

At the same time, monitoring programs have not detected clear evidence of dramatic population growth among the species most often associated with serious attacks. Data collected through shark net programs suggest that changes in shark abundance alone may not account for the rising number of incidents.

Researchers emphasize that shark behavior, prey availability, environmental conditions and human activity patterns likely interact in complex ways. These factors can vary significantly across regions and seasons, making it difficult to identify a single national explanation.

The challenge for scientists is compounded by the rarity of shark bites relative to the millions of recreational visits made to Australian beaches each year. Because serious incidents remain uncommon, establishing statistically robust conclusions can be difficult.

For coastal communities, however, recent attacks have reinforced concerns about safety in the ocean. While experts continue to investigate the drivers behind the increase, they stress that the overall risk of a shark attack remains low despite the upward trend in incidents.

Researchers argue that understanding how climate change, marine ecosystems and human behavior intersect will be critical to improving risk assessments and informing public safety measures. Until clearer answers emerge, Australia’s growing number of shark encounters is likely to remain a subject of public debate and scientific investigation.

Nearly 90 years after a strange marine carcass was discovered inside the stomach of a sperm whale off the coast of Canada, scientists, cryptozoologists and marine historians remain divided over whether the remains represented an unknown species or a decomposed basking shark, one of the Pacific Ocean’s most elusive and heavily persecuted marine animals.

The mystery dates back to October 1937, when workers at a whaling station in Haida Gwaii recovered a 3-metre carcass from a sperm whale caught in waters off the Pacific coast. Witnesses described the creature as having a dog-like head, a camel-shaped nose, a reptilian body and a horse-like tail. The remains were reportedly coated in a thin white layer.

The carcass was placed on a platform assembled from wooden crates and photographed before an image appeared on the front page of a regional newspaper on 31 October 1937. The discovery quickly became linked to local stories about “Cadborosaurus,” a legendary marine cryptid said to inhabit the waters of the Salish Sea and the Pacific Northwest.

No biological samples from the carcass survive today, leaving researchers to rely entirely on a small number of black-and-white photographs and eyewitness testimony. The absence of physical evidence has allowed competing interpretations of the discovery to persist for decades.

John Kirk, president of the British Columbia Scientific Cryptozoology Club, argues that the remains belonged to an unidentified marine species rather than a known shark. Kirk has cited interviews with whaling station workers, including one flenser involved in removing the carcass from the whale.Kirk contends that scientific institutions prematurely dismissed the discovery.

He has also pointed to a second alleged Cadborosaurus specimen discovered in 1968 near Naden Harbour, southeast of Haida Gwaii, which was later discarded after museum officials identified it as a fetal baleen whale.“We lost a massive discovery here because of misidentification,” Kirk said in interviews discussing the case.

He has maintained that the 1937 remains possessed hair-like structures inconsistent with shark anatomy and argued the carcass more closely resembled a marine mammal than a reptile or fish.Most marine biologists, however, reject the theory that the remains represented an unknown species. They instead identify the carcass as a decomposing basking shark, a species once common off the coast of British Columbia before government eradication campaigns sharply reduced its population.

Basking shark are the second-largest fish species in the world and can exceed 10 metres in length. Unlike most sharks, they feed passively on plankton near the water’s surface. Because their skeletons are composed primarily of cartilage rather than bone, their bodies undergo dramatic transformations during decomposition.

Ben Speers-Roesch, a marine biologist at the University of New Brunswick, said decomposing basking sharks often create what scientists call the “pseudo-plesiosaur carcass” phenomenon. As the shark’s gill structures collapse and soft tissue deteriorates, the remains can appear to have a long neck, small head and paddle-like appendages resembling extinct marine reptiles.

“With a long spinal cord and a small head at the end, it looks like a mythological sea serpent,” Speers-Roesch said, noting that unfamiliarity with shark decomposition can lead observers to misidentify carcasses.Marine scientists have cited similar cases elsewhere.

In 1977, the Japanese fishing vessel Zuiyō Maru recovered a decomposed carcass off the coast of New Zealand that some initially believed represented a surviving plesiosaur. Subsequent amino acid analysis determined the remains belonged to a basking shark.Speers-Roesch acknowledged that the 1937 Canadian photographs differ slightly from typical basking shark carcasses because of how the remains were displayed after recovery.

He also noted that juvenile basking sharks have occasionally been found inside sperm whales, making the scenario biologically plausible.“The mystery has persisted because it has elements that are not as easily identifiable as a basking shark,” he said. “But so much of the carcass captures what we know about basking sharks and how they decompose.”

The debate over the Cadborosaurus photographs has increasingly intersected with renewed scientific attention on basking sharks themselves. Once abundant in Pacific waters near Vancouver Island, the species became the target of official eradication programs during the mid-20th century.

In 1955, the Canadian federal government launched a campaign to eliminate basking sharks after the animals were blamed for damaging salmon fishing nets. Authorities equipped patrol vessels with large blades mounted on their bows, devices locally described as “razor-billed shark slashers.”Scott Wallace, a former fisheries scientist who authored a 2007 federal report classifying the species as endangered in British Columbia waters, said the vessels intentionally rammed sharks at the surface.

“They simply cut them in half,” Wallace said in accounts describing the program.Government estimates indicate at least 413 basking sharks were deliberately killed during the following 14 years, while another 1,500 may have died through fishing-net entanglements. Additional mortality occurred through a short-lived commercial fishery targeting shark liver oil. Scientists estimate that as many as 2,600 sharks, representing more than 90% of the regional population, were eliminated.

The eradication campaign formed part of broader marine predator control policies implemented during the period. Fisheries authorities also targeted seals, sea lions and orcas around salmon fishing grounds. In the early 1960s, officials installed a .50-calibre machine gun on a coastal island for use against killer whales, although records indicate the weapon was never deployed.

Today, basking sharks are protected under Canadian federal law. It is illegal to kill, harm or capture the species in British Columbia waters, and federal recovery plans remain in place. Fisheries officials have nevertheless stated that recovery of the population could take up to 200 years.

Interest in the species resurfaced after a rare basking shark sighting off the British Columbia coast in 2024 renewed scientific and public attention on the animals and the history of their decline.For cryptozoologists such as Kirk, the absence of definitive proof continues to sustain theories that unknown marine species may still inhabit the Pacific depths.

Marine scientists, however, argue the case ultimately demonstrates how limited human understanding remains when interpreting rare ocean phenomena, especially when decomposition dramatically alters the appearance of marine animals.