Big whale sharks’ small food, video


This 5 June 2019 video, recorded in the Sea of Cortez in Mexico, says about itself:

This Marine Behemoth’s Favorite Food is Practically Microscopic

The whale shark is one of the largest creatures in the sea – which makes it particularly ironic that its diet is composed almost entirely of one of the smallest: plankton.

Advertisements

Holding sharks, how to do it


This 26 May 2019 video says about itself:

In this season 5 excerpt, Jonathan learns from master shark handler Neal Harvey how to put a shark into tonic immobility and then pick it up!

Sand tiger sharks return to US shipwrecks


This December 2016 video from the USA says about itself:

Sand Tiger Sharks of North Carolina | JONATHAN BIRD’S BLUE WORLD

Jonathan heads to North Carolina to explore the offshore shipwrecks of the “Graveyard of the Atlantic” which have become home to Sand Tiger sharks. The sharks are unwitting bodyguards to small fish seeking protection from predators and have developed a clever way to hide from the fish and to hover with perfect buoyancy control.

JONATHAN BIRD’S BLUE WORLD is an Emmy Award-winning underwater science/adventure program that airs on public television in the United States.

From Duke University in the USA:

Sand tiger sharks return to shipwrecks off N.C. coast

Coast’s hundreds of shipwrecks are important habitats for vulnerable shark species

April 22, 2019

Summary: A study reveals shipwrecks off North Carolina’s coast are important habitats for sand tiger sharks, whose population plummeted in the 1980 and 1990s. Photos taken months and even years apart by scuba divers show female sand tiger sharks returning to the same shipwrecks. The photos were uploaded to the citizen-science program Spot A Shark USA which used specialized software to ID the sharks.

Photos taken months, and in some cases years, apart by scuba divers show female sand tiger sharks returning to the same shipwrecks off the North Carolina coast, a new study co-led by scientists at Duke University reveals.

This display of “site fidelity” by the sharks suggests the shipwrecks are important habitats for the fierce-looking but docile species, which experienced dramatic population drops toward the end of the last century and is listed as globally vulnerable by the International Union for Conservation of Nature (IUCN).

“Their population is estimated to have dropped by as much as or more than 75 percent in the 1980s and 1990s and we don’t know if it has stabilized or is still declining, in large part because we’ve mostly had to rely on anecdotal sightings,” said Avery B. Paxton, a visiting scholar at the Duke University Marine Laboratory in Beaufort, North Carolina and lead author of the study.

“Having photographic evidence that these wrecks form an important habitat the sharks return to from time to time gives us a focal point for ongoing research so we can better understand how the species is faring,” she said.

“We’re now trying to figure out why they return. They could be using the wrecks as rest stops along their migratory paths, but they could also be returning here for mating or possibly to give birth. There are all kinds of hypotheses our team is testing,” said Paxton, who formerly was a postdoctoral researcher at the South-East Zoo Alliance for Reproduction & Conservation.

She and her colleagues published their peer-reviewed paper April 22 in Ecology.

Having access to photos taken by citizen scientists, including images uploaded to the Spot A Shark USA program led by the North Carolina Aquariums, was vital to the study’s success.

“This area is called the Graveyard of the Atlantic for a reason — it has hundreds of wrecks. As researchers, we can’t have eyes underwater at each of them,” Paxton said. “Being able to rely on scuba divers and other citizen scientists who are out there and have cameras with them extends our reach.”

Each sand tiger shark has a unique pattern of brown spots on its skin that acts like a fingerprint, allowing scientists to identify individual sharks and distinguish them from others of their species.

By analyzing and comparing the spot patterns on sharks in divers’ photos dating back to 2007, Paxton and her colleagues identified six female sand tiger sharks that have returned to the same wrecks, or to similar wrecks close by, at intervals ranging from one to 72 months apart.

“This is the first time we’ve been able to document site fidelity to habitats in offshore waters along the East Coast,” Paxton said. “Previous studies have shown similar behavior patterns in Australia and Africa and in estuarine habitats such as Delaware Bay, so what we are finding off North Carolina definitely fits into global patterns.”

Male sharks may also exhibit site fidelity to wrecks off the North Carolina coast, but so far no matching photos have been found to prove it.

That may change as more and more citizen scientists share their images, said Hap Fatzinger, director of the North Carolina Aquarium at Fort Fisher and a co-author of the study.

“Through collaborations and strong partnerships, Spot A Shark USA is engaging recreational divers to become citizen scientists and provide essential data to expand our knowledge,” Fatzinger said. “By increasing community engagement, we are creating stronger connections to local, regional and global concerns for sharks and healthy ocean ecosystems.”

Erica Blair, a graduating senior at Duke and a co-author of the new study, helped map the unique spot patterns on the sharks’ skin that were used to confirm their identities. Brian Silliman, Rachel Carson Associate Professor of Marine Conservation Biology at Duke’s Nicholas School of the Environment, also co-authored the study.

Great white sharks scared of killer whales


This video says about itself:

This Is The Biggest Great White Shark Ever Caught On Camera

Great white sharks are… big. Obviously. But a few years ago, divers met up with Deep Blue, probably the biggest great white shark ever caught on camera. So what do we know about the massive great white?

From the Monterey Bay Aquarium in the USA:

White sharks flee feeding areas when orcas present

Electronic tag data reveals white sharks do not return until following season; elephant seals benefit

April 16, 2019

Summary: New research challenges the notion that great white sharks are the most formidable predators in the ocean. The research team documented encounters between white sharks and orcas at Southeast Farallon Island off California. In every case examined by the researchers, white sharks fled the island when orcas arrived and didn’t return there until the following season. Elephant seal colonies in the Farallones also indirectly benefited from the interactions.

New research from Monterey Bay Aquarium and partner institutions published today in Nature Scientific Reports challenges the notion that great white sharks are the most formidable predators in the ocean. The study “Killer Whales Redistribute White Shark Foraging Pressure On Seals” shows how the great white hunter becomes the hunted, and the elephant seal, the common prey of sharks and orcas, emerges as the winner.

“When confronted by orcas, white sharks will immediately vacate their preferred hunting ground and will not return for up to a year, even though the orcas are only passing through,” said Dr. Salvador Jorgensen, senior research scientist at Monterey Bay Aquarium and lead author of the study.

The research team — which included Jorgensen and Monterey Bay Aquarium scientist Scot Anderson, and research partners from Stanford University, Point Blue Conservation Science and Montana State University — documented four encounters between the top predators at Southeast Farallon Island in the Greater Farallones National Marine Sanctuary, off San Francisco, California. The scientists analyzed the interactions using data from 165 white sharks tagged between 2006 and 2013, and compiled 27 years of seal, orca and shark surveys at the Farallones.

“The research in this paper combines two really robust data sources,” said Jim Tietz, co-author of the study and Farallon Program Biologist at Point Blue Conservation Science. “By supplementing the Aquarium’s new shark tagging data with Point Blue’s long-term monitoring of wildlife at the Farallon Islands National Wildlife Refuge, we were able to conclusively show how white sharks clear out of the area when the orcas show up.”

In every case examined by the researchers, white sharks fled the island when orcas arrived and didn’t return there until the following season.

Elephant seal colonies in the Farallones also indirectly benefited from the interactions. The data revealed four to seven times fewer predation events on elephant seals in the years white sharks left.

“On average we document around 40 elephant seal predation events by white sharks at Southeast Farallon Island each season,” Anderson said. “After orcas show up, we don’t see a single shark and there are no more kills.”

Each fall between September and December white sharks gather at the Farallones to hunt for young elephant seals, typically spending more than a month circling Southeast Farallon Island. Transient orcas also feed on elephant seals, but only show up occasionally at the island.

To determine when orcas and sharks co-occurred in the area, researchers compared data from the electronic shark tags with field observations of orca sightings. This made it possible to demonstrate the outcome on the rare instances when the predators encountered each other.

Electronic tags showed all white sharks began vacating the area within minutes following brief visits from orcas. Sometimes the orcas were only present for less than an hour. The tags then found the white sharks either crowded together at other elephant seal colonies farther along the coast or headed offshore.

“These are huge white sharks. Some are over 18 feet long (5.5 meters), and they usually rule the roost here,” Anderson said. “We’ve been observing some of these sharks for the past 15 to 20 years — and a few of them even longer than that.”

The study’s findings highlight the importance of interactions between top predators, which aren’t well-documented in the ocean.

“We don’t typically think about how fear and risk aversion might play a role in shaping where large predators hunt and how that influences ocean ecosystems,” Jorgensen said. “It turns out these risk effects are very strong even for large predators like white sharks — strong enough to redirect their hunting activity to less preferred but safer areas.”

The researchers drew no conclusions about whether orcas are targeting white sharks as prey or are bullying the competition for the calorie-rich elephant seals.

“I think this demonstrates how food chains are not always linear,” Jorgensen said. “So-called lateral interactions between top predators are fairly well known on land but are much harder to document in the ocean. And because this one happens so infrequently, it may take us a while longer to fully understand the dynamics.”

Diver woman petting Bahamas sharks, video


This 29 March 2019 video says about itself:

Petting Sharks like Dogs?! | Blue Planet Live | BBC Earth

Cristina Zenato is the woman who isn’t afraid to hug sharks.

Cristina Zenato caresses her sharks in the warm Bahamas waters, the animals seem to like the suit’s touch on their skin and stop in her lap for a quick stroke.

Bahamas sharks, BBC video


This 26 March 2019 video says about itself:

Sharks in the Bahamas | Blue Planet Live | BBC Earth

Watch the new promo for Blue Planet Live! BBC One will air the program at 8 pm on Wednesday 27th March for the UK audience and BBC Earth will air at 3 pm for the Canada Audience.

Steve Backshall dives with tiger and hammerhead sharks in the Bahamas. Here shark fishing is illegal and the booming population helps the local economy by means of underwater tourism.

Diver meets sharks in Bahamas waters


This 19 March 2019 video says about itself:

Come face to face with several species of sharks at Tiger Beach, while on expedition with conservationist Jim Abernethy. Shark diving generates millions of dollars every year in the Bahamas, where the apex predators are protected by the government and there is a $5,000 fine for shark fishing.