Feb.24, 2015 at 3:56 pm, under Shark News Stories
Great white sharks (Carcharodon carcharias) grow and reach sexual maturity at much slower rates than previously believed, according to a press release from NOAA Fisheries. A study completed in 2014 and published online last month in the journal of Marine & Freshwater Research used carbon-14 dating and vertebral band pair counts of 81 white shark specimens, collected in the western North Atlantic Ocean, to develop a growth curve for the species. According to the results, female white sharks reach sexual maturity at approximately 33 years of age, while males reach maturity at approximately 26 years. Additionally, the results of the study indicate that the life-span of white sharks could exceed 70 years, which places them among one of the longest living species of fish.
The latest findings on the growth rates and life-span of white sharks provides important information for conservation efforts of the species. Low reproduction rates coupled with slow growth and maturation rates could potentially put the species at greater risk for population decline, since losses in populations are not quickly replaced. Great white sharks are a protected species in U.S. waters and legally must be released live, if captured. However, individual white sharks are sometimes killed as a result of incidental by-catch from commercial fisheries, so it is important that these types of incidents be managed to protect the welfare of white shark populations, as a whole.
For more information, check out NOAA Northeast Fisheries Science Center press release,
and the Marine and Freshwater Research journal article,
Feb.20, 2015 at 2:43 pm, under Shark Videos
Samsung is promoting it’s head-mounted Gear VR display with some 360-degree footage of great white shark diving off Port Lincoln, Australia. Head-mounted displays like the Gear VR and Occulus Rift offer viewers an immersive experience that can simulate a completely different environment.
I shot some similar white shark footage using the Kolor Abyss 360 rig at Isla de Guadalupe, Mexico, last September. This footage should be compatible with both the Samsung Gear VR and Occulus. If you don’t have a head-mounted display, you can still take advantage of the 360-degree effect, using your mouse to click and drag to change the angle.
Check out the 360-degree great white shark video
Nov.23, 2014 at 3:47 pm, under Shark News Stories
The following was shared with us by shark researcher Michelle Jewell…
Stealthy seals use subsurface structures to sneak by white sharks
Written by Michelle Jewell (@ExpatScientist)
Predators are highly influential in ecosystems because of the many top-down effects they can have. The most obvious and direct way predators influence an ecosystem is by eating and reducing the number of prey animals in the system, but another equally important way is the indirect influence they have on the behaviour of prey animals.
If you have avoided parking on a risky-looking street, taken a different route between classes to avoid a bully, or abandoned a forest hike because of snapping twigs in the distance, you have been indirectly affected by perceived ‘predators’. In the wild, prey animals will also change their behaviour when they perceive that predators are around, and these altered behaviours often influence other species, ultimately shaping the ecosystem.
My research has focused on these same principles of predator/prey interactions in the ocean, and a great place to study oceanic predators and their prey are Cape fur seal colonies in South Africa. Every summer (November), Cape fur seals give birth to thousands of pups, and by winter (April – September) these ‘young-of-the-year’ seals begin to venture off their islands to swim offshore to the fishing grounds with the adults. These young-of-the-years are typically slow, plump from months of a mostly fat milk diet, and – most importantly – naïve. White sharks take advantage of this naivety and aggregate around seal colonies every winter. Young-of-the-year pups are forced to learn how to avoid sharks quickly or suffer some rather permanent consequences. This means that during a full year, every seal colony goes through a period of high white shark presence (winter) and very low to no white shark presence (summer). Therefore, we are able to study how seals act ‘normally’ during the summer when there are no/very few sharks and how they change their behaviour in the winter to avoid white sharks.
Also, there are many different kinds of seal colony islands along the coast, which lets us ask more questions about how seals use their environment to avoid sharks. I conducted my study at the Dyer Island/Geyser Rock system, which is home to ‘Shark Alley’ as well as many shallow reefs, kelp forests, and shipwrecks. About 100km to the east is another seal colony called Seal Island, which is a world-famous spot to see white sharks predate on seals, but this island system lacks the abundant nearby structures/reefs/kelp forests that are present at Geyser Rock. By looking at these two different kinds of islands, we can also examine how structures – or ‘refugia’ – may alter how seals avoid white sharks at Geyser Rock from how seals avoid white sharks at Seal Island.
Research Conducted by Marine Dynamics a Shark Cage Diving Operator in Gansbaai South Africa
Do all of these structures and anti-predatory tactics of Cape fur seals change white shark movements around Geyser Rock? Most definitely! Check out that study and infographic!
For more information, check out the detailed scientific publication in Behavioral Ecology & Sociobiology.
Big thanks to Michelle for sharing her research and awesome infographic! For more from Michelle check out her Michelle’s Expat Scientist blog.
Sep.10, 2014 at 1:03 pm, under Shark Videos
Vimeo user Edwar Herreño recently added a video documenting six killer whales (Orcinus orca) hunting a tiger shark (Galeocerdo cuvier) off Cocos Island. The orcas appear to use a team effort to huntand appear and then drown the shark in the video. The video description says that the orcas fed on the shark after killing it.
Aug.13, 2014 at 2:33 pm, under Opinions in the media
Much like last year’s mockumentary “Megalodon: The Monster Shark Lives”, Discovery Channel’s first episode of this year’s Shark Week has come under fire for it’s fictional account of “Submarine,” a giant man-eating great white shark with roots in a South African urban legend. “Shark of Darkness: Wrath of Submarine” plays out like a documentary, though it’s actually just an account of fictional events, plagued with less-than-convincing acting and special effects, in the eyes of many viewers.
Twitter was lit up with disgruntled viewers on Sunday night when the episode premiered, and numerous online media outlets have since voiced their distaste in Discovery’s decision to peddle out another faux “documentary.”
In Discovery’s defense, the show did contain the following vague disclaimer.
Events have been dramatized, but many believe Submarine exists to this day.
While most viewers realized from the get-go that this is a piece of fiction, others bought into it as a real-life account of a ‘monster shark’ with an appetite for humans. “Submarine” was noted to have an “insatiable taste for human blood,” and had adapted methods to attack humans more efficiently.
Is this really the kind of message Discovery Channel should be sending its viewers about sharks?
You can check some other opinions about Shark of Darkness by following the links below.