United States diver discovers megalodon shark teeth


This 5 October 2019 video from South Carolina in the USA says about itself:

I found huge megalodon shark teeth while scuba diving in the Cooper River. Huge thanks to Captain Alan Devier for putting us onto an amazing site. This was a very exciting diving adventure! I can’t wait to do this again! Who else enjoys finding shark teeth?

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How great white sharks feed, new research


This 19 September 2019 video says about itself:

Wildlife expert Steve Backshall dives with the ocean’s ultimate predator, the Great White Shark, in the waters off Guadalupe Island, Mexico.

From the Research Organization of Information and Systems:

Technology provides insight into how white sharks hunt

October 2, 2019

White sharks are top predators in the marine environment, but unlike their terrestrial counterparts, very little is known about their predatory activity underwater, with current knowledge limited to surface predation events. Now, a team of international scientists has used video- and data-logging technology to shed new light on predator-prey interactions of these mighty sea creatures.

Their findings were published on July 4, 2019 in Marine Ecology Progress Series.

The white shark is an iconic species found in surface- and deep-waters in all major oceans of the world. With a lifespan that can stretch 70 years or more, these formidable predators can reach over six meters (20 feet) in size when fully mature. They prey on marine mammals, such as seals, as well as fish, and are responsible for more shark bites on humans than any other shark.

“Their breaching behavior — where they jump out of the water to catch seals — observed in South Africa, is especially famous, and has attracted the attention of a lot of people, including scientists,” said Yuuki Watanabe, associate professor in marine biology at the National Institute of Polar Research in Japan and lead author of the study.

“Although breaching behavior can be seen from boats and is well studied, what happens underwater is mostly unknown,” Watanabe added. “Moreover, in other aggregation sites of white sharks, including our study site in Australia, breaching behavior is rarely seen, suggesting that different hunting strategies are employed by these sharks.”

To gain a better understanding of the strategies white sharks use to scout and hunt their prey, the researchers needed to dive deeper — literally. “That’s why we decided to attach video cameras and other sensors to white sharks to directly observe their underwater hunting behavior on seals,” explained Watanabe, who has been engaged in biologging research for many years and has made unique discoveries about the ecology of marine life.

The international research team, including Watanabe and his colleague Charlie Huveneers (associated professor at Flinders University in Australia), lured sharks to their research boat by throwing ‘chum’ into the shark inhabited waters off Neptune Islands Marine Park in Australia. Chum, a fishy bait mixture consisting of fish blood and flesh, is very effective at attracting sharks due to their highly developed sense of smell. Using a deployment pole, metal clamps containing a data logging package were placed onto the front edge of the dorsal fins of eight white sharks. The data loggers included an accelerometer that recorded swim speed, depth and water temperature at one second intervals. It also recorded triaxial acceleration (measurements of body movement across three perpendicular axis) at shorter intervals. The data-logging package fitted onto three of the sharks also contained a tiny video camera, which recorded video footage for six hours at pre-programmed intervals. After 1-2 days, the data logger packages detached from the shark and were located and recovered on the surface using radio signals. The researchers then analyzed the accelerometer records and linked them to the video footage.

Acceleration data recorded by these devices allowed researchers to distinguish behavioral patterns while the animals were out of view by measuring tailbeat movement frequency.

“We obtained video footage showing how a white shark chased a seal in the water. In Japanese, we say ‘seeing is worth of a thousand words.’ This is also the case for ecological studies of marine animals,” said Watanabe.

The video footage showed one of the sharks attacking a seal. During this event, the attached data logger recorded intensive swimming action with a rapid burst in lateral acceleration, tailbeat frequency and swim speed. After analyzing 150 hours of recorded acceleration data, the researchers identified seven potential predation events at various depths ranging from the surface to a depth of 53 meters (174 feet). These predation events occurred both at nighttime and during the twilight hours of dawn and dusk, which partially contrasts with the breaching behavior observed by white sharks hunting seals in South African coastal waters that primarily occurs at dawn and dusk.

These findings suggest that white sharks do not only prey on seals on the surface (attacking from below after searching for a seal silhouetted against the surface, illuminated by the sunlight shining from above) with the momentum of their upward thrust causing them to leap into the air in a breaching motion, as observed in South Africa. At the study site in Australia, sharks also actively search and pursue seals in deeper waters, and this predatory activity is not limited to dawn and dusk but rather also occurs at night, suggesting that white sharks do not depend on vision to locate and hunt their prey.

The researchers would like to get more footage of seal-hunting behavior of sharks to understand variations. “It appears that hunting strategies of white sharks in South Africa are very different to those in Australia, and we would like to understand what kinds of factors (biological or non-biological) are driving the difference,” he explained.

How basking sharks dive, new research


This 2015 video says about itself:

Breaching Basking Sharks | World’s Weirdest

Basking sharks have weird ways of ridding themselves of parasites.

From the University of Exeter in England:

Basking sharks exhibit different diving behavior depending on the season

September 26, 2019

Tracking the world’s second-largest shark species has revealed that it moves to different depths depending on the time of year.

Basking sharks spend most of the summer months at the ocean’s surface, but dive to deeper depths in winter.

This seasonal variation in behaviour is likely caused by environmental conditions: sharks could be exploring different areas of the ocean to deal with changes in food abundance.

Basking sharks also perform “yo-yo” dives towards late winter and early spring. “Yo-yo” dives are rapid and repeated movements between deep and surface waters.

Whilst performing these dives, several of the studied sharks reached depths of over 1000 m, and two were tracked as far as 1500 m below the surface.

Dr Phil Doherty, a postdoctoral researcher at the University of Exeter’s Penryn Campus and lead author of the study, said: “We do not know exactly why the sharks are performing these dives. They may be sampling the water column in efforts to detect prey, or attempting to re-orientate themselves for navigation purposes.”

Dr Doherty and his colleagues from the University of Exeter teamed up with Scottish Natural Heritage, MarAlliance, Manx Basking Shark Watch and Wave Action to study how the movements and diving behaviour of basking sharks change throughout the year.

The team attached satellite tags to 32 of these gentle giants off the coast of Scotland from a boat and monitored their movements. The tags collected data on depth and temperature, along with ambient light levels, which can be used to estimate the sharks’ location each day.

The collected data reveal a seasonal change in diving behaviour, it also showed that basking sharks move to different depths depending on the time of day.

“We found that sharks spent most of the summer near the surface of the water, occupying the top few metres during the day, moving down to depths of 10-25 m at night. But in winter, they did the opposite, spending the majority of time between 50 and 250 m, but more often shallower during the night,” said Dr Doherty.

Moving to shallower depths during the day and diving down at night is referred to as “reverse diel vertical migration.” All three planktivorous sharks — basking sharks, whale sharks and megamouth sharks — have been shown to display this behaviour.

Scientists believe that it enables them to track their main food source, plankton. Like basking sharks, plankton can remain close to the ocean’s surface during the summer and move to deeper depths to over winter.

Dr Doherty and his team hope to use their study as a starting point for further investigations to identify “depth hotspots” of basking shark activity.

Dr Suzanne Henderson, from Scottish Natural Heritage, said: “It’s great to see further analysis and publication of the data collected in 2012-2014. Behaviour at depth is the most challenging to obtain and understand and this adds to that knowledge for basking sharks.”

Basking sharks are a protected species considered as “threatened” globally, with the north-east Atlantic population considered “endangered”. Understanding their diving behaviour and preferred depths could help determine where shark presence overlaps with different types of fishing gear.

This information could be used to reduce the risk of incidental catch of these sharks by commercial fisheries, although we don’t know to what extent these sharks are at risk in Scottish waters. It could also help inform conservation measures to better protect sharks and their habitat.

Blacktip sharks of Florida, USA


This 22 September 2019 video from the USA says about itself:

Jonathan visits shark biologist Dr. Stephen Kajiura at Florida Atlantic University and learns how he studies huge schools of Blacktip sharks that appear in the winter off the coast of Florida. Using airplanes, drones and of course boats, Dr. Kajiura has learned why these sharks come to Florida in huge numbers every year.

Fluorescent marine animals, video


This 23 August 2019 video says about itself:

The allure of fluorescence in the ocean

Why do so many marine animals have bright fluorescent pigments? This video describes how one function was demonstrated experimentally.

Fluorescence is a process where high-energy light temporarily excites electrons in a molecule. When the molecule relaxes, the energy is re-emitted as a lower-energy photon with a longer wavelength. For example, blue or violet light is often used to excite green, yellow, or red fluorescent emission. Fluorescence is a passive physical property of many molecules, and unlike bioluminescence it is not something that animals can actively turn on and off.

One of the most famous molecules in all of science is Green Fluorescent Protein (GFP). It was first discovered in a bioluminescent jellyfish, and later found in non-luminous corals, sea anemones, and other organisms. These proteins have proven so useful in laboratory and clinical settings that in 2008, the original GFP researchers were awarded the Nobel Prize in Chemistry. Yet despite the many ways that humans use the fluorescent proteins, we don’t really know the ways that the animals use them.

To test how animals might use fluorescence we conducted predator-prey experiments with the flower-hat jellyfish. We found that the fluorescent tentacle tips, when excited by ambient blue light from the environment, were an irresistible attractant to potential prey (a supernormal stimulus; see Tinbergen 1948). We also found evidence for fluorescent structures in a range of other predators.

You might have heard about fluorescent sharks and turtles, but just because something is fluorescent doesn’t mean it’s serving a useful function (see Mazel 2017). Even your own teeth and fingernails are fluorescent, but that is just because of their chemical composition.

For this video, we filmed the fluorescence of animals by shining a blue light on them and putting a yellow filter in front of the lens. The filter blocks out the excitation light but lets the fluorescent light be recorded. You can try it at home with a piece of yellow plastic and a blue LED flashlight. You might be surprised what you find!

Shark tagged from submarine, first time ever


This 9 September 2019 video says about itself:

Shark Tagged From Submarine For First Time In History | National Geographic

For the past year, a research team has developed a new strategy to study the near-threatened bluntnose sixgill shark in deep waters.