Philippines whale sharks video


This video says about itself:

1 June 2018

Jonathan travels to Oslob, Cebu, Philippines to swim with wild whale sharks that are actually fed every day for the tourists. We used to joke about “chumming” for an animal that eats mostly plankton, but in Oslob, they are actually doing it, and making thousands of people into shark lovers along the way.

Do you think feeding the whale sharks is OK? Or wrong? Please leave us a comment, but please be polite.

Surprise! This shark looks like a male on the outside, but it’s made babies. Bigeye houndsharks found off India’s coast had female reproductive systems, by Yao-Hua Law, 10:00am, July 10, 2018.

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Lemon sharks video


This video says about itself:

Lemon Sharks Hunt Trevally | BBC Earth

23 June 2018

The shallows give lemon sharks the chance to catch fish that would normally outrun them.

Great white sharks dive deep, new research


This video says about itself:

21 July 2017

Watch OCEARCH’s video showing the process of tagging [great white shark] Mary Lee.

Video courtesy: OCEARCH

Read WTOP’s articles on Shark Week here.

From the University of Washington in the USA:

Great white sharks dive deep into warm-water whirlpools in the Atlantic

June 18, 2018

Summary: Tracking data from two great white sharks reveals that they spend more time deep inside warm-water eddies, suggesting that’s where they like to feed.

It’s always good to know where great white sharks are likely to be swimming. That’s true if you’re a nervous beachgoer, a fishing boat trying to avoid illegal bycatch, or a marine biologist hoping to conserve this vulnerable species.

A study from the University of Washington and Woods Hole Oceanographic Institution looked at the movements of adult female white sharks in the Gulf Stream and North Atlantic Ocean. Results showed, surprisingly, that they prefer warm-water eddies — the clockwise-spinning whirlpools in the ocean — and tend to spend more time deep inside these slowly spinning features.

The open-access study was published in May in Scientific Reports.

“We’ve decimated some open-ocean shark populations to a fraction of what they were 100 years ago. And yet we don’t know the basics of their biology”, said lead author Peter Gaube, a senior oceanographer at the UW’s Applied Physics Laboratory. “If we know where those sharks, or turtles or whales might be in the open ocean, then the fisheries can avoid them, and limit their bycatch.”

Gaube investigates how ocean eddies, or whirlpools, influence the behavior of marine animals. His previous study, on loggerhead sea turtles, similarly found that they prefer the anticyclonic, or clockwise-spinning, eddies. These features trap large amounts of water at the ocean’s surface and are most often warm, clear and low in nutrients.

The new study analyzes movements of two female great white sharks tagged in September 2012 off Cape Cod and in March 2013 off Jacksonville, Florida. The tricky job of tagging the animals was done by OCEARCH, a nonprofit that focuses on tagging and tracking sharks. One shark just had a position tag, while the other had a second tag that also recorded temperature and depth. The sharks were tracked for nearly 6 years, with one still reporting its position regularly, as they swim north with the Gulf Stream and then out into the open ocean.

The high-tech tags are made by Wildlife Computers in Redmond, Washington. The early shark-tagging projects could just offer rough ideas of where sharks were swimming, Gaube said. But since precise satellite position networks were made available to the public, and with improvements in computing and batteries, the tags can now collect detailed information as sharks travel throughout the marine environment.

Researchers took the data from the two sharks and compared their position in the ocean with sea-surface height data from satellites showing where the huge, swirling warm- and cold-water eddies were located at that time.

“These eddies are everywhere, they cover 30 percent of the ocean’s surface,” Gaube said. “It’s like what you see if you’re walking along a river, and these eddies form behind rocks, but it happens on a different scale in the ocean: Instead of being a little thing that disappears after a few seconds, they can be the size of the state of Massachusetts, and can persist for months to years. You could be in the middle of an eddy in a ship and you’d probably never know it. The water may be a little warmer, and it could be a little clearer, but otherwise you wouldn’t know.”

Analysis shows that the two sharks spent significantly more time in warm-water eddies than the cold-water eddies that spin the other way. Sharks lounged the longest at about 450 meters (about a quarter of a mile) deep inside the warm-water eddies, especially during the daytime, likely feeding on the abundant fish and squid at these depths. They were more likely to come to the surface at night.

This preference goes against common wisdom, because it’s the cold-water eddies that generally bring nutrient-rich water up from the depths of the ocean, and satellite images show that cold-water eddies are rich in marine plant life. This study is the first to show that sharks gravitate toward eddies, and that they prefer the warmer variety.

“White sharks are effectively warm-blooded”, Gaube said. “They have to keep their body temperature elevated. We believe that these warm eddies allow white sharks to forage longer at depth, where most of the biomass in the open ocean is found. One reason that the sharks might prefer them is by diving in these warm eddies, they can spend more time in the deeper water.”

Second, recent studies suggest that the “twilight zone,” below the depths that satellites can see, contains many more fish than previously believed — and much more than at the surface. Those patterns might be different than the ones we can easily detect from space.

“Could these ‘ocean deserts’ actually be super productive at depth? That’s what we think might be happening”, Gaube said.

Some recent deep-sea net surveys have found larger, toothy fish like pomfret below the surface in anticyclonic eddies, which could provide a motivation for the sharks to dive there.

“These sharks are 2,800 pounds. It’s hard to imagine that they’re just eating krill and small fish all of the time they’re in the open ocean”, Gaube said. “If they can find pomfret and lots of squid in these eddies, then sharks can really get a meal out of that.”

Data collected by sharks could help to protect this “twilight zone” as it’s just beginning to be targeted by major fisheries, Gaube said. And information about where great white sharks like to hang out could help conserve this vulnerable species.

“Maybe if we understand the biology of these animals, how they use these features, we could say, ‘OK, do not fish anticyclonic eddies during this time of year, because you’re more likely to catch white sharks'”, Gaube said. “Instead of cordoning off a particular area, we could say there’s this feature, it moves every day, let’s make a ‘mobile marine protected area’ and not touch it because we know it’s a hot spot for great white sharks.”

Why whale sharks gather, new research


This 2016 video says about itself:

GoPro Awards: Ocean Ramsey and a Whale Shark

17 July 2016

Captured and submitted by GoPro Awards recipients Ocean Ramsey and Juan Oliphant.

Join shark biologist and freediver Ocean Ramsey as she films with whale sharks in the Philippines to document migrating populations. Whale shark populations are at an all-time low due to finning, fishing by catch, entanglement, speedboat prop collisions, and death by ingestion of floating debris.

To learn more about how you can help, visit here.

Shot 100% on the HERO4® camera from ‪http://GoPro.com.

From the University of York in England:

Secret to whale shark hotspots

June 8, 2018

A study has uncovered the secret to why endangered whale sharks gather on mass at just a handful of locations around the world.

The new insights into the habits of the world’s largest fish will help inform conservation efforts for this mysterious species, say the researchers.

Large groups of whale sharks congregate at only around 20 locations off the coasts of countries including Australia, Belize, the Maldives and Mexico. Why the sharks, which can reach more than 60 feet in length, choose these specific locations has long perplexed researchers and conservationists.

The new study, by researchers at the University of York in collaboration with the Maldives Whale Shark Research Programme (MWSRP), has found that the shark “aggregation sites” show many common characteristics — they are all in areas of warm, shallow water in close proximity to a sharp sea-floor drop off into deep water.

The researchers suggest that these sites provide the ideal setting for the filter-feeding sharks to search for food in both deep water and the warm shallows, where they can bask near the surface and warm up their huge bodies.

Supervising author of the study, Dr Bryce Stewart from the Environment Department at the University of York, said: “Sharks are ectotherms, which means they depend on external sources of body heat. Because they may dive down to feed at depths of more than 1,900 metres, where the water temperature can be as cold as 4 degrees, they need somewhere close by to rest and get their body temperature back up.

“Steep slopes in the sea bed also cause an upwelling of sea currents that stimulate plankton and small crustaceans such as krill that the whale sharks feed on.”

However, these perfectly contoured locations are not without their drawbacks due to human activity. Sharks swimming in shallow waters close to the surface are vulnerable to boat strikes caused by vessels ranging from large ships to tourist boats hoping to spot them.

Lead author of the paper Joshua Copping, who carried out the research while studying for a masters in Marine Environmental Management at the University of York, and is now working on a PhD at the University of Salford, said: “Individual whale sharks can be identified by their unique pattern of spots and stripes which allows researchers to follow specific sharks that visit these aggregation sites. That means we have a good idea of the rate and extent of injuries at each of these locations and sadly it’s generally quite high.”

Boat strikes, along with accidental trapping in fishing nets, and the targeted hunting of the species for their fins and meat, have contributed to an alarming decrease in global whale shark numbers in the past 75 years.

By highlighting what makes these areas important to the whale shark, the researchers hope this study will also highlight the importance of managing these areas carefully in order to minimise human impact on the shark’s habitat and behaviour.

Dr Stewart added: “The more we know about the biology of whale sharks the more we can protect them and this research may help us to predict where whale sharks might move to as our climate changes.

“Not only do we have an ethical responsibility to conserve this miraculous animal for future generations, but they are also extremely valuable to local people on the coastlines where they gather, which are often in developing countries. While a whale shark can be worth as much as $250,000 USD dead, alive it can provide more than $2 Million USD over the course of its life span.”

Co-author James Hancock from MWSRP added; “Whale sharks can travel huge distances around the globe and the existence of such a small number of known aggregation sites suggested there had to be something about the depth and shape of the underwater terrain in these areas that makes them appealing.

“It’s very exciting to have narrowed down some of the key reasons why whale sharks choose these specific areas. However, the main focus of this research was on costal aggregations which are largely made up of young sharks — exactly where the rest of the demographic hang out is still unclear.”

Zebra sharks off Oman, video


This video says about itself:

2 March 2018

Jonathan and cameraman Bill travel to the Daymaniat Islands in Oman in search of zebra sharks (also called leopard sharks in some parts of the world). The diving in Oman is fabulous! They encounter huge schools of fish, cuttlefish, sea turtles and finally…the elusive zebra shark. All while diving in 110° F heat!

JONATHAN BIRD‘S BLUE WORLD is an Emmy Award-winning underwater science/adventure series featuring underwater cinematographer/naturalist Jonathan Bird.

This zebra shark demanded a belly rub from the diver cleaning its tank.

First silky sharks seen off Saba, Caribbean


This 2015 video is called Shark experts are surrounded by exceptionally large silky sharks in Cuban waters.

From BioNews:

First silky shark sightings by Saba Conservation Foundation!

Whilst nurse sharks and Caribbean reef sharks are regularly spotted on the Saba Bank, it’s not every day that you see silky sharks. During a routine visit to the Saba Bank, a research team from the Saba Conservation Foundation (SCF), Saba Bank Management Unit, made history a few weeks ago when Oceaware’s Guido Leurs spotted around 10 juvenile silky sharks (Carcharhinus falciformis). This was the first time that silky sharks had been reported from the Saba Bank.

Some of the defining characteristics of the silky shark include a small, rounded first dorsal fin that originates behind the end of the pectoral fins, a much smaller second dorsal fin with a free tip that is twice as long as the height of the fin together with long, slender pectoral fins that typically have dusky tips.

These slender oceanic sharks get their name from the smooth, silky texture of their skin which is caused by dermal denticles that are unusually densely packed. Silky sharks inhabit both deep oceans and shallow coastal waters and are highly migratory.

The silky shark population in the Western Atlantic follows the Gulf Stream as well as the movements of tuna and swordfish, their main food source. Their appetite for these schooling fish makes them extremely vulnerable to by-catch, and many silky sharks are caught and killed in pelagic longline fisheries or are trapped in purse seines targeting tuna and swordfish.

There are also targeted silky shark fisheries in operation in the Caribbean and Gulf of Mexico, where they are caught by longlines.

Silky sharks are ranked amongst the three most important sharks in the global shark fin trade – with up to 1.5 million fins being traded annually from this species. Population data for this species shows a worrying downwards trend since the early 1990s, especially in the northwest and western central Atlantic. The IUCN Red List status of the silky shark was adjusted in 2017 from “Near Threatened” to “Vulnerable” due to an estimated 47-54% decline of the global population over three generations.

Silky sharks are especially vulnerable to exploitation because of their life history characteristics: a long gestation period, a slow growth rate, small litters and a long reproductive period. Safeguarding the future of this highly migratory species will require a cooperative approach between all countries through which it migrates, and an increase in safe havens like the Yarari Sanctuary and the Saba Bank.

More information is here.

Great white shark research and conservation


This 2015 video is called Australia. The Great White Shark | Full Documentary.

From the Monterey Bay Aquarium in the USA:

White shark researchers tap data from electronic tags to gain insights into survival rates

May 9, 2018

Summary: Researchers have tagged juvenile white sharks for nearly two decades, tracking their movements in coastal waters of the Northeastern Pacific. Now they’ve tapped those data in a new way, gaining the first empirical estimate of annual survival rates for young white sharks and quantifying the role fishing plays in the rate of white shark deaths.

Tagging in Southern California and Mexico shows most shark deaths are due to unintentional capture in fishing gear, highlighting the value of best practices that support protected species’ recovery. The results are published today in the Journal of Applied Ecology.

Researchers in the United States and Mexico have tagged juvenile white sharks for nearly two decades, tracking their movements in coastal waters of the Northeastern Pacific. Now — drawing on methods used to study mountain lions, coyotes, moose and other terrestrial animals — they’ve tapped those data in a new way, gaining the first empirical estimate of annual survival rates for young white sharks and quantifying the role fishing plays in the rate of white shark deaths.

The study, “Juvenile survival, competing risks, and spatial variation in mortality risk of a marine apex predator,” published today in the Journal of Applied Ecology, confirms that unintentional capture in fishing gear (bycatch) is the greatest cause of death for young white sharks, a protected species in both Mexico and the United States.

More broadly, data from pop-up archival tags (PAT tags) — which have been used worldwide to track tens of thousands of individual ocean animals, including white sharks — represent “a widely-available, untapped data source that could dramatically increase our understanding of marine population ecology,” said lead author Dr. John Benson, an assistant professor at the University of Nebraska.

Benson, who primarily studies terrestrial predators, conducted the white shark study as a postdoctoral researcher at Monterey Bay Aquarium. The aquarium — together with colleagues at California State University, Long Beach; Aquatic Research Consultants in San Pedro, Calif.; and the Ensenada Center for Scientific Research and Higher Education (CICESE) in Baja California — has been tagging and tracking juvenile white sharks since 2002.

Research results at a glance

Data from 37 sharks tagged since 2002 revealed that:

  • The overall estimated annual survival rate for young white sharks was 63 percent. Though this study did not address broad trends in the white shark population in the Northeastern Pacific, the researchers note that protection of white sharks in 1994 has likely resulted in a reduction in fishing-related mortality. The increase in juvenile shark sightings over the last 15 years may be an early indication of a positive sign for population recovery.
  • Fisheries bycatch was the main source of mortality for juvenile white sharks in the region, highlighting the need to follow best practices related to incidental catch in coastal commercial and sport fisheries. Only two young white sharks tagged by researchers died of natural (non-fishing) causes.
  • Overall mortality risk for young white sharks was lower for larger animals, which could be attributed to smaller sharks being more abundant, or simply more susceptible to capture in gillnets.

According to Benson, the paper adds to scientific understanding of white sharks, and shows how models that estimate survival rates for top predators on land — data obtained from radio telemetry and tracking collars — can be applied to ocean species that carry PAT tags.

“We always learn things from adjacent fields,” said Dr. Salvador Jorgensen, principal white shark scientist at the Monterey Bay Aquarium and senior coauthor on the paper. “Before coming to the aquarium, John made his name studying mountain lions in Southern California. We were excited to see how the methodologies John was using for land-based predators could be applied in the ocean.”

Taking a new approach

Benson realized that data from PAT tags opened the door to a new approach to estimate survival rates for young sharks, using what are called known-fate models.

“Because the PAT tags record detailed data on temperature and diving, it is possible to reconstruct the fate of the shark in the final minutes of each track,” said Jorgensen.

The technique hinges on being able to determine the fate of individual animals — data that PAT tags provide. If a tagged shark was eaten by a predator, or if it died in a fishing net, the tag recorded those data.

By applying known-fate models to those data, researchers estimated survival and mortality rates for the population at large. They also determined that fisheries bycatch was the main source of mortality for juvenile white sharks in the Northeastern Pacific, and that juveniles were at significantly greater risk of mortality when in Mexican waters.

Protections are in place

In California, it is illegal to target and land white sharks, and coastal waters are permanently closed to all gillnets within three miles of shore. In Baja California and throughout Mexico, targeting and landing white sharks is prohibited all year. However, gillnet fishing in coastal waters is still permitted for other species. Data from the study show that juvenile white sharks are an estimated nine times less likely to get entangled in California compared with Baja.

“We are learning that the gillnet regulations in California, although originally designed to protect sport fishing interests, have done a lot to protect juvenile white sharks,” said Dr. Chris Lowe, director of the Shark Lab at CSU Long Beach and a coauthor of the paper.

The study also revealed that juvenile white shark mortality in gillnets is reduced when nets are checked by fishermen every 6 to 12 hours, so the young sharks can be released alive.

“In terms of reducing white shark mortality, avoiding setting nets close to shore and checking them frequently appear to be the best practices,” Lowe said.

Coauthor Oscar Sosa-Nishizaki, a professor at CICESE, stressed that engaging with local fishermen in Mexico is critical to reducing mortalities and improving recovery prospects for the Northeastern Pacific white shark population.

“It’s the best way to go,” he said. “Mexican fishing communities play a vital role in enabling this research as well as helping us solve any issues as they arise.”

CICESE doctoral student Emiliano García-Rodríguez, another coauthor, added: “It’s very important to work with the fishermen, because we want to know whenever they incidentally catch a white shark.”

“This research suggests the importance of a collaborative approach to management in California and Mexico, and opportunities to innovate on best practices that can support fishermen, research and protections for white sharks,” Jorgensen said.

Other co-authors on the study include John O’Sullivan, director of collections at Monterey Bay Aquarium; Chuck Winkler of Aquatic Research Consultants; and Connor F. White, white shark researcher with CSU Long Beach.

Additional information about this study and other white shark research is available on the aquarium’s Future of the Ocean blog (futureoftheocean.wordpress.com/).