What If There Were No Sharks?

By Mindy Weisberger - Senior Writer 3 days ago Animals

What would the oceans look like if all of the sharks disappeared

Sharks are magnificent predators that represent an impressive evolutionary success story. They've swum the oceans for more than 400 million years, diversifying over time to inhabit rivers and lakes as well. About 500 known species are alive today, and there are likely even more yet to be discovered.

Sharks can be huge, like the massive whale shark (Rhincodon typus); or human-hand-size, like the pocket shark (Mollisquama parini). However, it's the great white shark (Carcharodon carcharias) that typically commands the public's imagination. These sharks have a reputation for aggressiveness toward people, shaped by decades of terrifying portrayals in movies. In fact, these fearful pop-culture portraits of great whites are so pervasive that they might lead some people to wonder if the world would be better off with no sharks at all.

But what might the oceans look like if all of the sharks disappeared? 

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Sharks and rays to be given new international protections

25 August 2019

Countries have agreed to strengthen protections for 18 threatened species of sharks and rays, including those hunted for their meat and fins.

The proposal was passed at the Convention on International Trade in Endangered Species (CITES) on Sunday.

The newly protected species include mako sharks, wedgefishes and guitarfishes.

A demand for shark fin soup is one of the driving factors in the depleting numbers of sharks in the ocean.

The proposal, which was tabled by Mexico and requires ratification this week, means that the species can no longer be traded unless it can be proven that their fishing will not impact the possibility of their survival.

The number of sharks killed each year in commercial fisheries is estimated at 100 million, with a range between 63 million and 273 million, according to The Pew Trust.

Makos, the fastest shark species, have almost disappeared completely from the Mediterranean and numbers are diminishing rapidly in the Atlantic, Northern Pacific and Indian oceans.

Although 102 countries voted in favour of the move, 40 - including China, Iceland, Japan, Malaysia and New Zealand - opposed it.

Some argued that there was not enough evidence to show that mako sharks were disappearing as a result of fishing.

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Mediterranean sharks risk 'disappearing': conservationists

JULY 12, 2019

Sharks—the sea's top predators for millions of years—are at risk of disappearing from the Mediterranean as overfishing and plastic pollution choke populations of the endangered hunters, conservationists warned Friday.

The World Wildlife Fund (WWF) said that more than half of shark and ray species in the Mediterranean were under threat, and that almost a third of them have been fished to the brink of extinction.

Its report, released ahead of Shark Awareness Day, singled out Libya and Tunisia as the worst culprits, with each country's fishery hauling in about 4,200 tonnes of sharks a year—three times that of the next biggest Mediterranean fisher, Italy.

While some species are targeted for food, many of the sharks fished in the Mediterranean are bycatch caught up in nets set for other fish.

The WWF said it had recorded more than 60 shark species entangled in fishing nets across the Mediterranean.

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Hundreds of sharks and rays tangled in plastic

JULY 5, 2019

by University of Exeter

Hundreds of sharks and rays have become tangled in plastic waste in the world's oceans, new research shows.

University of Exeter scientists scoured existing published studies and Twitter for shark and ray entanglements, and found reports of more than 1,000 entangled individuals.

And they say the true number is likely to be far higher, as few studies have focussed on plastic entanglement among shark and rays.

The study says such entanglement—mostly involving lost or discarded fishing gear—is a "far lesser threat" to sharks and rays than commercial fishing, but the suffering it causes is a major animal welfare concern.

"One example in the study is a shortfin mako shark with fishing rope wrapped tightly around it," said Kristian Parton, of the Centre for Ecology and Conservation on Exeter's Penryn Campus in Cornwall.

"The shark had clearly continued growing after becoming entangled, so the rope—which was covered in barnacles—had dug into its skin and damaged its spine.

"Although we don't think entanglement is a major threat to the future of sharks and rays, it's important to understand the range of threats facing these species, which are among the most threatened in the oceans.

"Additionally, there's a real animal welfare issue because entanglements can cause pain, suffering and even death."

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Satellites used to protect endangered sharks

By Helen Briggs BBC News

8 April 2019

Satellites scanning the oceans are a valuable new tool to protect sharks, according to scientists.

A review of evidence suggests endangered sharks can be protected from threats such as illegal fishing, using the technology.

Whales, turtles and birds are already being monitored from space, raising hopes that the technique can be applied in the conservation of other species.

Many sharks are on the brink of extinction.

Populations of sharks, rays and skates (elasmobranchs) have declined dramatically over the past 50 years.

"New technologies such as this are going to be really important to the conservation of sharks," said Michael Williamson of the Zoological Society London (ZSL) and King's College, London.

Over-fishing is one of the biggest causes of the decline in sharks, through accidental or illegal targeting.

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'Wiped out before our eyes': Hawaii offers bold plan to stop shark killings

Proposed law would protect any shark or ray in state waters and be first of its kind in US

Breena Kerr in Maui

Fri 8 Feb 2019 23.00 GMTFirst published on Fri 8 Feb 2019 11.00 GMT

Sharks could soon become more numerous in Hawaii waters – and advocates say that’s a good thing.

Lawmakers in Honolulu advanced a proposed ban on killing sharks in state waters on Wednesday, after receiving hundreds of calls and letters of support from around the country. The law, which would provide sweeping protection for any shark, rather than select species, could be the first of its kind in the United States.

“These amazing animals are getting wiped out before our eyes, and people don’t even realize what they’re missing out on,” said Ocean Ramsey, a Hawaii-based shark conservationist, researcher and tour operator who has been instrumental in lobbying for the bill, in an interview with the Guardian. Last month, a photo of Ramsey swimming with a 6-metre (20ft) great white shark off the coast of Oahu went viral.

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UK fish and chip shops are selling endangered sharks, DNA tests prove

People buying generic fish such as rock could in fact be eating a range of shark species

Patrick Barkham

Thu 31 Jan 2019 10.00 GMT Last modified on Thu 31 Jan 2019 18.55 GMT

Fish and chip shops and fishmongers are selling endangered sharks to an unwitting public, according to researchers who used DNA barcoding to identify species on sale.

Most chip shop fish sold under generic names such as huss, rock, flake and rock salmon turned out to be spiny dogfish, a shark species classified as endangered in Europe by the International Union for the Conservation of Nature’s red list.

Researchers at the University of Exeter also found fins of shark species unknowingly sold by a British wholesaler included scalloped hammerheads, which are endangered globally, as well as shortfin mako and smalleye hammerhead sharks.

Other species sold in fish and chip shops and fishmongers included starry smooth-hounds, nursehounds and blue sharks.

It was illegal to catch spiny dogfish in the EU until 2011 but the fish is now permitted to be sold as bycatch – when it is brought up in nets that target other species.

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Who's tougher? Baby sharks or daddy sharks?

January 3, 2019, Florida Atlantic University

It's not just their teeth and jaws that people find intriguing. It's also their funky shapes and unique skeletal makeup that capture attention. Unlike humans and most land animals, sharks have mineralized cartilage skeletons instead of bones. This allows them to move at unbelievable speeds through the water. Since cartilage weighs less than bone and is less dense, sharks can bend, swim, and maneuver in the ocean much differently than their bony fish counterparts.

Because sharks vary in size and shape, there is great diversity in their morphology, physiology and how they swim. For example, the common thresher shark relies on its tail to stun prey when feeding, and the size of its vertebrae and their mechanics may explain why it depends on a strong and long tail that operates like a whip. To move this way requires low stiffness and toughness, or a lower resistance to deformation and ability to absorb energy, respectively.

A shark's vertebral column is governed by dynamic and complex interactions among tissue composition and morphology, and there are many differences in growth, mineralization and mechanical properties.

Scientists from Florida Atlantic University's Charles E. Schmidt College of Science and the National Marine Fisheries Service, National Oceanic and Atmospheric Administration (NOAA), predicted that the solid central part of the vertebrae in mature, older sharks would be stiffer and tougher. So they decided to put their theory to a test.

They examined cartilage mechanics from six species of sharks under biologically relevant conditions along the length of their bodies and over a range of ages. They looked at small, infant (young of year) sharks, immature sharks and mature sharks from each of six different species: the dusky shark (Carcharhinus obscurusp); the porbeagle (Lamna nasus); and charismatic sharks like the great white shark (Carcharodon carcharias); the shortfin mako (Isurus oxyrinchus) and the common thresher shark (Alopias vulpinus).

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World's strangest sharks and rays 'on brink of extinction'

By Helen Briggs BBC News

4 December 2018

Some of the world's most unusual sharks and rays are on the brink of extinction because of threats such as commercial fishing, scientists have said.

A shark that uses its tail to stun prey and a ray half the length of a bus are on the list of 50 species.

The scientists say sharks have a bad image and people do not understand how important and threatened they are.

And losing even one of these "living fossils" would wipe out millions of years of evolutionary history.

"The biggest myth around sharks is definitely the perception that they are dangerous, that they are man-eating machines - they're not," marine biologist Fran Cabada told BBC News.

"There have been some negative interactions recorded but they are very infrequent and they're not intentional."

This is the first time sharks, rays and chimeras (fish with cartilage in place of bones) have been assessed for the Edge (Evolutionarily Distinct and Globally Endangered) of Existence programme.

Most sharks are at the top of the food chain, which makes them crucial to the health of the oceans.

Losing them would have a big impact on other fish populations and, ultimately, human livelihoods.

"They have very few relatives on the tree of life, so they are very unique and losing them will actually represent a big, big loss," said Fran Cabada.

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Getting a grip on the slow but unique evolution of sharks

Date:  October 8, 2018

Scientists at the RIKEN Center for Biosystems Dynamics Research (BDR) in Japan, in collaboration with other Japanese institutes and aquariums, have decoded the whole genomes of two shark species for the first time and improved the whale shark genome sequences released previously. By analyzing the genomes and comparing them with those of other vertebrate species, they have constructed an overview of their unique life histories and evolutionary paths. This work was published online in Nature Ecology and Evolution.

Advances in genome sequencing have made it possible to compare genomes from different species, giving us insights into their evolutionary histories and characteristics. While data for many organisms are available, to date, genome sequencing for sharks has been hampered by their huge genomes, which are even larger than the human genome. The notable exception is the elephant shark, although strictly speaking this fish is not professionally classified as a true shark.

Sharks have many unique characteristics, including their body structures, reproductive systems, way of sensing, and extreme longevity -- a shark species is known to live for more than three centuries. Fully decoded shark genomes will be a tremendous help to research aimed at discovering the molecular bases for these qualities. With this ultimate goal in mind, a research team led by Shigehiro Kuraku at RIKEN BDR analyzed shark genomes using cutting-edge DNA sequencing technologies and comparative bioinformatics that were able to deal with gigabase-scale sequences. They chose two primary species -- the brownbanded bamboo shark and the cloudy catshark -- because they can be raised in aquariums, making it relatively easy to constantly obtain live specimen. They also performed an improved assembly of the whale shark genome, which had been previously released.

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Sharks Get Bigger Home Protected by Mexican Navy

By Laura Geggel, Senior Writer | July 22, 2018 08:03am ET

Sharks can finally breathe a sigh of relief. Their home in Mexico's Revillagigedo National Park — North America's largest marine protected area — is now protected by none other than the Mexican navy, thanks in large part to a team of dedicated researchers.

This expansive upgrade didn't happen overnight. Rather, the hard work of researchers, who spent years tagging and tracking sharks, has finally translated into political policy, making the park's extension a reality.

"I'm very excited," James Ketchum, who helped tag the sharks while a graduate student at the University of California, Davis, and is now the conservation director of Palagíos Kakunjá, a nongovernmental organization for marine conservation, said in a statement published by UC Davis. "It shows all these years of work have been useful for something." [In Photos: Mexico's New Ocean Reserve Protects Stunning Biodiversity]

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Sharks love jazz but are stumped by classical, say scientists

A study at Macquarie University in Sydney found that sharks could recognise jazz – if there was food on offer

Ben Beaumont-Thomas

Thu 10 May 2018 10.21 BSTLast modified on Thu 10 May 2018 22.00 BST

Researchers at Sydney’s Macquarie University have discovered that sharks can recognise jazz music.

In a paper published in Animal Cognition, the researchers, led by Catarina Vila Pouca, trained juvenile Port Jackson sharks to swim over to where jazz was playing, to receive food. It has been thought that sharks have learned to associate the sound of a boat engine with food, because food is often thrown from tourist boats to attract sharks to cage-diving expeditions – the study shows that they can learn these associations quickly.

The test was made more complex with the addition of classical music – this confused the sharks, who couldn’t differentiate between jazz and classical. “It was obvious that the sharks knew that they had to do something when the classical music was played, but they couldn’t figure out that they had to go to a different location,” said researcher Culum Brown. “The task is harder than it sounds, because the sharks had to learn that different locations were associated with a particular genre of music, which was then paired with a food reward. Perhaps with more training, they would have figured it out.”

Vila Pouca added: “Sharks are generally underestimated when it comes to learning abilities – most people see them as mindless, instinctive animals. However, they have really big brains and are obviously much smarter than we give them credit for.” She said that the evidence would hopefully prompt more conservation work.

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Why sharks like it hot - but not too hot

By Helen BriggsBBC News

13 March 2018

Scientists have calculated the water temperature at which tiger sharks are most active and abundant.

They say the sharks, which are second only to great whites in attacking people, prefer a balmy 22C.

Shark populations may shift range as the oceans heat up, bringing them into greater conflict with humans, according to the scientific study.

For instance, tiger sharks may move into waters off Sydney in both winter and summer months.

Dr Nicholas Payne of Queen's University Belfast and the University of Roehampton led the research.

"Our study suggests that 22 degrees is not too cold for the animals and it's not too hot for them," he said. "It's about right in terms of their optimal preference for temperature."

Cold blooded

Most sharks are cold blooded. Their body temperatures match the temperature of the water around them.

The research, reported in the journal Global Change Biology, could lead to new ways to predict when and where tiger shark attacks might happen.

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Stress test: New study finds seals are stressed-out by sharks

Researchers test the effects predators have on their prey's cortisol levels in the wild

Date:  December 6, 2017

Source:  University of Miami Rosenstiel School of Marine & Atmospheric Science

Summary:

While a little added stress may be helpful to flee a dangerous situation, or to meet an approaching deadline, it's no secret that prolonged exposure to the stress hormone cortisol is linked to health problems. So, what effects does stress have on animals in the wild that need to navigate the same waters as the ocean's top predator -- great white sharks?

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Snack attack: alligators like to eat sharks, study reveals

Researchers find alligators preying on small sharks in Atlantic and Gulf

‘The frequency of one predator eating the other is really about size dynamic’

Oliver Milman in New York

Tuesday 17 October 2017 22.20 BSTLast modified on Tuesday 17 October 2017 23.37 BST

American alligators are frequently seen ambling around golf courses in Florida as players warily compete their rounds. But new research suggests the reptiles partake in a far more outlandish habit when away from the greens – eating sharks.

US researchers have documented instances of alligators preying upon small sharks along the Atlantic and Gulf coasts. A study, published in the journal Southeastern Naturalist, claims to be the first scientific study of the largely unseen struggle between the two feared predators.

“The frequency of one predator eating the other is really about size dynamic,” said James Nifong, a researcher at Kansas State University. “If a small shark swims by an alligator and the alligator feels like it can take the shark down, it will, but we also reviewed some old stories about larger sharks eating smaller alligators.”

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Endangered sharks, rays further threatened by global food markets

Using DNA barcoding technology, University of Guelph researchers discover a majority of the shark fins and manta gills sold around the world are from endangered species.

Date: August 25, 2017

Source: University of Guelph

Summary:

A majority of shark fins and manta ray gills sold around the globe for traditional medicines come from endangered species, a study has revealed. Using cutting-edge DNA barcoding technology, researchers found 71 per cent of dried fins and gills collected from markets in Canada, China and Sri Lanka came from species listed as at-risk and therefore banned from international trade.

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Sharks show novel changes in their immune cancer-related genes

January 30, 2017

A new genomics study of shark DNA, including from great white and great hammerhead sharks, reveals unique modifications in their immunity genes that may underlie the rapid wound healing and possibly higher resistance to cancers in these ocean predators. This research brings us a few steps closer to understanding, from a genetic sense, why sharks exhibit some characteristics that are highly desirable by humans.

Sharks and rays are well known to be highly efficient wound healers, and suspected to show a greater resistance to cancers, though this needs further study. These properties are likely tied to their immune systems, which have been fine-tuned over 400 million years of evolution.

A study by the Nova Southeastern University (NSU) Save Our Seas Shark Research Center and Guy Harvey Research Institute (GHRI) and the Cornell University College of Veterinary Medicine just published in the journal BMC Genomics (lead author, postdoctoral associate Nicholas Marra,) now provides the first evidence that some shark and ray immunity genes have undergone evolutionary changes that may be tied to these novel immune system abilities.

"The immune system of sharks and rays has been battle-tested and evolved over hundreds of millions of years," said Mahmood Shivji. Ph.D., director of NSU's Save Our Seas Shark Research Center and Guy Harvey Research Institute. "Using genomics approaches to understanding their immunity genesis is likely to produce many more exciting discoveries, some of which could potentially translate into human medical benefit. Now we have another important reason to make sure we don't lose these marvelous and ecologically critical animals to overfishing, as is currently occurring in many parts of the world. We've just scratched the surface in terms of learning what these ancient animals can teach us, as well as possibly provide us in terms of direct biomedical benefits."

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Examining the social networks of sharks

Date: October 4, 2016

Source: University of Delaware

Thanks to movies like "Jaws," we tend to think of sharks as loners who prefer to do their own thing. But if the ocean were a mixer, they'd actually be networking their fins off, not standing in the corner staring at their iPhones.

New research conducted at the University of Delaware found that sharks prefer to travel in groups of various sizes and spend a surprising amount of time together. Some individuals even spent up to 95 consecutive hours together over the course of the year.

Researchers gathered this data by using a novel tagging procedure to collect tens of thousands of interactions between 300 or so tagged sand tiger sharks along the Eastern Seaboard. They also documented interactions between sand tigers and seven other fish species.

The findings, published in the Nature journal Scientific Reports, could help researchers in future efforts to improve the life cycle of sand tiger sharks.

Documenting shark encounters in the open ocean

The project began in summer 2012, when UD researchers tagged 20 sand tiger sharks with implanted acoustic transceivers to study their interactions and movements. When the scientists recovered the tags from two male sand tiger sharks in 2013, the downloaded data told an unexpected story.

"Based on previous work, we knew that during the summer the sand tiger population formed groups in the Delaware Bay, with male and female adults and juveniles all together in the same places, sometimes very close together," said Danielle Haulsee, the paper's lead author and a doctoral student in the College of Earth, Ocean, and Environment's School of Marine Science and Policy.

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How do shark teeth bite? Reciprocating saw, glue provide answers

Date: September 8, 2016

Source: University of Washington

Sharks have a big reputation for their teeth. The ocean predators use their buzz saw mouths to efficiently dismantle prey, ranging from marine mammals and sea turtles to seabirds and -- as Hollywood likes to remind us -- an occasional human.

There are more than 400 species of sharks in the world and each has a unique tooth shape. Some are simple triangles, while others are deeply notched or spear-shaped. But despite this variety, scientists haven't detected a difference in how different shark teeth cut and poke tissue.

A recent University of Washington study sought to understand why shark teeth are shaped differently and what biological advantages various shapes have by testing their performance under realistic conditions. The results appeared in August in the journal Royal Society Open Science.

"When you have all these different tooth shapes, there should be some functional reason. That issue was fundamentally troubling to me," said senior author Adam Summers, a UW professor of biology and of aquatic and fishery sciences. "It seemed likely what we were missing is that sharks move when they eat."

Sharks shake their heads rapidly when they bite their prey, so evaluating how teeth perform while in a side-to-side motion was critical to the study tests, which took place during a summer marine biology course at the UW's Friday Harbor Laboratories on San Juan Island.

Summers and his collaborators affixed three different types of shark teeth to the blade of a reciprocating power saw, then cut through thick slices of Alaska chum salmon at a speed that mimicked the velocity of head-shaking as a shark devours its prey.

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