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.

Advertisements

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/).

Whale shark Anne’s new world record


This December 2017 video is called BEAUTIFUL COUPLE OF WHALE SHARKS SPOTTED IN THE SAUDI RED SEA.

From the Smithsonian Tropical Research Institute in Panama:

Whale shark logs longest-recorded trans-Pacific migration

April 26, 2018

Summary: A whale shark named Anne swam all the way across the Pacific from Coiba National Park in Panama to the Marianas Trench, setting a record as the longest-recorded migration.

Little is known about the world’s largest living fish, gentle giants reaching 12 meters (40 feet) in length. Researchers from the Smithsonian Tropical Research Institute (STRI) and colleagues tracked a female whale shark from the eastern Pacific to the western Indo-Pacific for 20,142 kilometers (more than 12,000 miles), the longest whale shark migration route ever recorded.

STRI marine biologist Héctor M. Guzmán tagged a female whale shark (Rhincodon typus) near Coiba Island in Panama, the largest island off of the coast of Central America, a National Park, World Heritage Site and marine protected area. His team named the shark Anne for conservationist Anne McEnany, president and CEO of the International Community Foundation (ICF). The multi-year project also tagged 45 additional sharks in Panama with sponsorship from Christy Walton’s Candeo Fund at the ICF, along with STRI and Panama’s science and technology bureau (SENACYT).

Guzmán estimated Anne’s position based on signals from a Smart Position and Temperature (SPOT) tag tethered to the shark, received by the Advanced Research and Global Observation Satellite (ARGOS). The tag only communicates with the satellite when the shark swims near the surface. Anne remained in Panamanian waters for 116 days, then swam toward Clipperton Island (France), nearing Cocos Island (Costa Rica) en route to Darwin Island in the Galapagos (Ecuador), a site known to attract groups of sharks. 266 days after she was tagged, the signal disappeared, indicating that Anne was too deep to track. After 235 days of silence, transmissions began again, south of Hawaii. After a nine-day stay, she continued through the Marshall Islands until she arrived at the Marianas Trench, a canyon in the ocean floor near Guam in the Western Pacific where movie director James Cameron located the deepest point on the Earth’s surface almost 11,000 meters (36,000 feet) below sea level.

Whale sharks dive to more than 1900 meters (6000 feet). But it is unknown what the animal was doing in this area.

“We have very little information about why whale sharks migrate,” said Guzmán. “Are they searching for food, seeking breeding opportunities or driven by some other impulse?”

“Despite being the world’s largest fish, it’s amazing to me how little we know about this species”, said Scott Eckert, co-author and biology professor at Principia College. “When I first began working on them, their taxonomy was debated, and it still wasn’t clear how they reproduced.”

Found in warm, tropical and sub-tropical waters, it is thought that about a quarter of whale sharks live primarily in the Atlantic, whereas about three-fourths live in the Indo-Pacific. Tourists are drawn to sites where 500 or more whale sharks gather: in Oman, Australia, Galapagos, Mexico, Mozambique and the Seychelles. Large groups are also reported from Taiwan, Southern China and the Gujarat coast of India.

Genetic studies show that whale sharks across the globe are closely related, indicating that they must travel long distances to mate. Whale sharks have been tracked for shorter distances along similar routes, but this report is the longest-recorded migration to date and the first evidence of a potential trans-Pacific route. Like Anne, other whale sharks appear to follow the North Equatorial Current for most of the distance. Large females can swim an average of 67 kilometers (about 40 miles) per day.

The whale shark is one of only three known filter-feeding sharks, feeding on plankton, fish eggs, krill, crab larvae as well as small squid and fish (and, accidentally, plastic, which they cannot digest). As such, they are not considered to be particularly dangerous, and tourism companies that offer the opportunity to swim very close to whale sharks are common near areas where they aggregate in large numbers. But their size also attracts fishing boats. They are sought after for their fins and meat, for their teeth (used for crafts and sold to tourists) and for cartilage and oil with purported medicinal value. Juvenile whale sharks often end up as bycatch in tuna and other fisheries.

Whale sharks were classified as endangered in 2016. During the past 75 years, it is estimated that nearly half of the world’s whale sharks have disappeared. In many parts of the world, whale sharks have legal protection, but regulations are often not enforced. Guzman’s data were used to design and draft local and regional policies for the protection of the species. Fishing, capture and sale of whale sharks are prohibited in Panama by Executive Decree No. 9, signed in 2009. In 2014, Panama’s environmental authority passed an additional resolution regulating whale shark watching in Coiba National Park and the Isla Canales de Afuera marine reserve. The resolution includes a Whale Shark Watching Manual but unfortunately, tourism activities are not well organized and the authorities are not present to enforce the regulations.

“Whale sharks in Coiba have already changed their behavior to avoid the surface and tourists”, Guzman said. “These studies are critical as we design international policy to protect transboundary species like the whale sharks and other highly migratory marine species.”

Diving for extinct Megalodon shark teeth


This video from the USA says about itself:

1 December 2017

Jonathan Bird goes to South Carolina with Cameraman Tim to meet Alan Devier, a world-renown shark tooth hunter and dive for fossilized Megalodon shark teeth in the murky depths of the Cooper River.

JONATHAN BIRD’S BLUE WORLD is an Emmy Award-winning underwater science/adventure program.

Shark evolution video


This video says about itself:

A timeline Of SHARK EVOLUTION (prehistoric till present day)

12 April 2018

Sharks are 450 million years old and have been on this planet longer than almost any other animal. They have lived through every major mass extinction event and have survived long past many of their competitors. With over 3,000 species spanning nearly half a billion years, sharks are one of the most evolutionarily successful animals to ever live. Tracking their evolutionary history, we can learn about these amazing species and how they came to their modern forms.

Most of the sharks on the planet have developed in the Cenozoic era, except for the truly ancient sharks from the Cretaceous period. The newest shark species to enter the water is the Hammerhead Shark. Hammerhead Shark evolution only dates back about 20 million years. Currently there are around 440 species of shark swimming in our oceans, however every year scientists are finding more unique species.

Time line of shark evolution

1. 514 million years ago : Metaspriginna was the oldest known fish-a sector of all jawed vertebrates.
2. 370 million years ago : Cladoselache was the earliest and most well-known shark. Its jaw was fused to its head.
3. 330 million years ago : Falcaus had a dorsal spine and large eyes w.r.t to its tiny body.
4. 320 million years ago : Stetacanthus had tooth-like skin preventing injury
5. 290 million years ago : Helicoprion had a jaw curved into a swirl shape. By this time sharks were able to grow teeth faster.
6. 180 million years ago : Hybodus had extremely sharp canine teeth and flat grinders in the back like a modern day bull shark.
7. 100 million years ago : Ginsu shark was one of the most modern sharks of its time.
8. 55 million years ago : Otodus was huge (30ft-39ft in length). It was the earliest known relative of all mackerel sharks.
9. 15.9 million years ago : Megalodon, meaning BIG TOOTH was one of the largest and fiercest predators ever. Fossil remains of megalodon suggest that this giant shark reached a length of about 59+ ft.