Elusive Sailback Shark Rediscovered After 50 Years

Sagumai et al. / Journal of Fish Biology, 2025

Every so often the animal kingdom just throws out a curveball that we’re not prepared for—like in 1970 when fishermen reeled in a freakish-looking shark and then it was never seen again.

Well 50 years later, that shark—so unique that it was declared a new genus—has finally been found again, confirming that the fishermen’s encounter wasn’t just a well-remembered dream.

Meet the sailback houndshark, believed to be endemic to the water’s of Papua New Guinea, and perhaps even to a single stretch of ocean called Astrolabe Bay. A group of fisherfolk reported that 5 of the sharks had been caught while a team of scientists were on the island conducting research for the country’s National Plan of Action on Sharks and Rays.

They had been caught incidentally at the mouth of a river that drains into the Astrolabe Bay, but had been sold as secondary catch since the meat is not prized by locals. Two years later, another was caught that turned out to be the first male sailfin houndshark ever seen.

A male and a female of the species were recently featured in a paper published in the Journal of Fish Biology. A curious predator, they have a large head but small mouth, and true to their name sport an elongated fin reminiscent of a sail on a yacht. Luckily for the shark, it is considered inferior on the market for Asian shark fin.

“Much remains unknown about its biology, ecology and population dynamics,” study corresponding author Jack Sagumai from the WWF Pacific division told the Australian Broadcasting Corporation. “Support is still needed to better understand the life history and ecology of this species.”

Papua New Guinea has several shark species known to inhabit nowhere else in the world’s oceans, so it’s possible the sailfin is one more of these so-called “microendemic” populations. Susceptible to even small changes in ecosystem, it’s likely the shark will require protection, but the first step to knowing how is to know the species, and the first scientific description will go a long way toward achieving that.

The authors write that the animal embodies “a unique evolutionary lineage of triakid sharks” (or houndsharks, containing about 40 species across nine genera) and that uniqueness could make it an important marine biodiversity “icon” for Papua New Guinea.“Monitoring and management options are currently being initiated as a precautionary approach to conserve this unique and rare species of shark,” the authors conclude. Elusive Sailback Shark Rediscovered After 50 Years

Read More........→September 11, 2025

South Africa’s great white sharks are changing locations – they need to be monitored for beach safety and conservation

South Africa is renowned for having one of the world’s biggest populations of great white sharks (Carcharodon carcharias). Substantial declines have been observed, however, in places where the sharks normally gather on the coast of the Western Cape province. Sharks congregate at these locations to feed, interact socially, or rest.

In Cape Town, skilled “shark spotters” documented a peak of over 300 great white shark sightings across eight beaches in 2011, but have recorded no sightings since 2019. These declines have sparked concerns about the overall conservation status of the species.

Conserving great white sharks is vital because they have a pivotal role in marine ecosystems. As top predators, they help maintain the health and balance of marine food webs. Their presence influences the behaviour of other marine animals, affecting the entire ecosystem’s structure and stability.

Marine biologists like us needed to know whether the decline in shark numbers in the Western Cape indicated changes in the whole South African population or whether the sharks had moved to a different location.

To investigate this problem, we undertook an extensive study using data collected by scientists, tour operators and shore anglers. We examined the trends over time in abundance and shifts in distribution across the sharks’ South African range.

Our investigation revealed significant differences in the abundance at primary gathering sites. There were declines at some locations; others showed increases or stability. Overall, there appears to be a stable trend. This suggests that white shark numbers have remained constant since they were given protection in 1991.

Looking at the potential change in the distribution of sharks between locations, we discovered a shift in human-shark interactions from the Western Cape to the Eastern Cape. More research is required to be sure whether the sharks that vanished from the Western Cape are the same sharks documented along the Eastern Cape.

The stable population of white sharks is reassuring, but the distribution shift introduces its own challenges, such as the risk posed by fisheries, and the need for beach management. So there is a need for better monitoring of where the sharks are.

Factors influencing shark movements

We recorded the biggest changes between 2015 and 2020. For example, at Seal Island, False Bay (Western Cape), shark sightings declined from 2.5 sightings per hour in 2005 to 0.6 in 2017. Shifting eastward to Algoa Bay, in 2013, shore anglers caught only six individual sharks. By 2019, this figure had risen to 59.

The changes at each site are complex, however. Understanding the patterns remains challenging.

These predators can live for more than 70 years. Each life stage comes with distinct behaviours: juveniles, especially males, tend to stay close to the coastline, while sub-adults and adults, particularly females, venture offshore.

Environmental factors like water temperature, lunar phase, season and food availability further influence their movement patterns.

Changes in the climate and ocean over extended periods might also come into play.

As adaptable predators, they target a wide range of prey and thrive in a broad range of temperatures, with a preference for 14–24°C. Their migratory nature allows them to seek optimal conditions when faced with unfavourable environments.

Predation of sharks by killer whales

The movement complexity deepens with the involvement of specialist killer whales with a taste for shark livers. Recently, these apex predators have been observed preying on white, sevengill and bronze whaler sharks.

Cases were first documented in 2015 along the South African coast, coinciding with significant behavioural shifts in white sharks within Gansbaai and False Bay.

Although a direct cause-and-effect link is not firmly established, observations and tracking data support the notion of a distinct flight response among white sharks following confirmed predation incidents.

More recently, it was clear that in Mossel Bay, when a killer whale pod killed at least three white sharks, the remaining sharks were prompted to leave the area.

Survival and conservation of sharks

The risk landscape for white sharks is complex. A study published in 2022 showed a notable overlap of white sharks with longline and gillnet fisheries, extending across 25% of South Africa’s Exclusive Economic Zone. The sharks spent 15% of their time exposed to these fisheries.

The highest white shark catches were reported in KwaZulu-Natal, averaging around 32 per year. This emphasised the need to combine shark movement with reliable catch records to assess risks to shark populations.

As shark movement patterns shift eastward, the potential change in risk must be considered. Increased overlap between white sharks, shark nets, drumlines (baited hooks) and gillnets might increase the likelihood of captures.

Beach safety and management adaptation

Although shark bites remain a low risk, changing shark movements could also influence beach safety. The presence of sharks can influence human activities, particularly in popular swimming and water sports areas. Adjusting existing shark management strategies might be necessary as distributions change.

Increased signage, temporary beach closures, or improved education about shark behaviour might be needed.

In Cape Town, for example, shark spotters have adjusted their efforts on specific beaches. Following two fatal shark incidents in 2022, their programme expanded to Plettenberg Bay. Anecdotal evidence highlights additional Eastern Cape locations where surfers and divers encounter more white sharks than before.

Enhanced monitoring and long-term programmes

Further research is required to understand the factors behind the movements of sharks and their impact on distribution over space and time. Our study underscores the importance of standardising data collection methods to generate reliable abundance statistics across their entire range. Other countries suffer from the same problem.

Additionally, we propose establishing long-term monitoring programmes along the Eastern Cape and continuing work to reduce the number of shark deaths.

Sarah Waries, a master’s student and CEO of Shark Spotters in Cape Town, contributed to this article.

Alison Kock, Marine Biologist, South African National Parks (SANParks); Honorary Research Associate, South African Institute for Aquatic Biodiversity (SAIAB), South African Institute for Aquatic Biodiversity; Alison Towner, Marine biologist, Rhodes University; Heather Bowlby, Research Lead, Fisheries and Oceans Canada; Matt Dicken, Adjunct Professor of Marine Biology, Nelson Mandela University, and Toby Rogers, PhD Candidate, University of Cape Town

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Read More........→September 21, 2023