Hammerhead sharks, new research

This 2016 video from Mexico is called Face to face with huge smooth hammerhead in Cabo San Lucas.

From Nova Southeastern University in the USA:

New shark research targets a nearly endangered species

September 15, 2020

They are some of the most iconic and unique-looking creatures in our oceans. While some may think they look a bit “odd”, one thing researchers agree on is that little is known about hammerhead sharks. Many of the 10 hammerhead shark species are severely overfished worldwide for their fins and in need of urgent protection to prevent their extinction.

To learn more about a declining hammerhead species that is data-poor but in need of conservation efforts, a team of researchers from Nova Southeastern University’s (NSU) Save Our Seas Foundation Shark Research Center (SOSF SRC) and Guy Harvey Research Institute (GHRI), Fisher Finder Adventures, the University of Rhode Island and University of Oxford (UK), embarked on a study to determine the migration patterns of smooth hammerhead sharks (Sphyrna zygaena) in the western Atlantic Ocean. This shark, which can grow up to 14-feet (400 cm), remains one of the least understood of the large hammerhead species because of the difficulty in reliably finding smooth hammerheads to allow scientific study.

To learn about smooth hammerhead behavior, the research team satellite-tagged juvenile hammerhead sharks off the US Mid-Atlantic coast and then tracked the sharks for up to 15 months. The sharks were fitted with fin-mounted satellite tags that reported the sharks’ movements in near real-time via a satellite link to the researchers.

“Getting long-term tracks was instrumental in identifying not only clear seasonal travel patterns, but importantly, also the times and areas where the sharks were resident in between their migrations,” said Ryan Logan, Ph.D. student at NSU’s GHRI and SOSF SRC, and first author of the newly published research. “This study provides the first high resolution, long term view of the movement behaviors and habitats used by smooth hammerhead sharks — key information for targeting specific areas and times for management action to help build back this depleted species.”

The researchers found that the sharks acted like snowbirds, migrating between two seasonally resident areas — in coastal waters off New York in the Summer and off North Carolina in the Winter. Their residency times in these two locations coincided with two environmental factors: warmer surface water temperatures and areas with high productivity — indicative of food-rich areas.

“The high-resolution movements data showed these focused wintering and summering habitats off North Carolina and New York, respectively, to be prime ocean “real estate” for these sharks and therefore important areas to protect for the survival of these near endangered animals,” said Mahmood Shivji, Ph.D., director of NSU’s GHRI and SOSF SRC, who oversaw the study.

Identifying such areas of high residency provides targets for designation as “Essential Fish Habitat” — an official title established by the US Government, which if formally adopted can subsequently be subject to special limitations on fishing or development to protect such declining species.

The tracking data also revealed a second target for conservation. The hammerheads spent a lot of resident time in the winter in a management zone known as the Mid-Atlantic Shark Area (MASA) — a zone already federally closed for seven-months per year (January 1 to July 31) to commercial bottom longline fishing to protect another endangered species, the dusky shark. However, the tracking data showed that the smooth hammerheads arrived in the MASA earlier in December, while this zone is still open to fishing.

“Extending the closure of the MASA zone by just one month, starting on December 1 each year, could reduce the fishing mortality of juvenile smooth hammerheads even more,” said Shivji. “It’s particularly gratifying to see such basic research not only improving our understanding of animal behavior in nature but also illuminating pathways for recovery of species and populations that have been overexploited so we can try and get back to a balanced ocean ecosystem.”

The tracks of the smooth hammerheads (and other shark species) can be found here.

Shark and bony fish evolution, new research

This 9 September 2020 video from England says about itself:

410-Million-Year-Old Fish Fossil Virtual 3D CT Scan

Virtual three-dimensional model of the braincase of Minjinia turgenensis generated from CT scan.

Credit: Imperial College London/Natural History Museum

From Imperial College London in England:

Ancient bony fish forces rethink of how sharks evolved

September 7, 2020

Sharks’ non-bony skeletons were thought to be the template before bony internal skeletons evolved, but a new fossil discovery suggests otherwise.

The discovery of a 410-million-year-old fish fossil with a bony skull suggests the lighter skeletons of sharks may have evolved from bony ancestors, rather than the other way around.

Sharks have skeletons made of cartilage, which is around half the density of bone. Cartilaginous skeletons are known to evolve before bony ones, but it was thought that sharks split from other animals on the evolutionary tree before this happened; keeping their cartilaginous skeletons while other fish, and eventually us, went on to evolve bone.

Now, an international team led by Imperial College London, the Natural History Museum and researchers in Mongolia have discovered a fish fossil with a bony skull that is an ancient cousin of both sharks and animals with bony skeletons. This could suggest the ancestors of sharks first evolved bone and then lost it again, rather than keeping their initial cartilaginous state for more than 400 million years.

The team published their findings today in Nature Ecology & Evolution.

Lead researcher Dr Martin Brazeau, from the Department of Life Sciences at Imperial, said: “It was a very unexpected discovery. Conventional wisdom says that a bony inner skeleton was a unique innovation of the lineage that split from the ancestor of sharks more than 400 million years ago, but here is clear evidence of bony inner skeleton in a cousin of both sharks and, ultimately, us.”

Most of the early fossils of fish have been uncovered in Europe, Australia and the USA, but in recent years new finds have been made in China and South America. The team decided to dig in Mongolia, where there are rocks of the right age that have not been searched before.

They uncovered the partial skull, including the braincase, of a 410-million-year-old fish. It is a new species, which they named Minjinia turgenensis, and belongs to a broad group of fish called ‘placoderms‘, out of which sharks and all other ‘jawed vertebrates’ — animals with backbones and mobile jaws — evolved.

When we are developing as foetuses, humans and bony vertebrates have skeletons made of cartilage, like sharks, but a key stage in our development is when this is replaced by ‘endochondral’ bone — the hard bone that makes up our skeleton after birth.

Previously, no placoderm had been found with endochondral bone, but the skull fragments of M. turgenensis were “wall-to-wall endochondral.” While the team are cautious not to over-interpret from a single sample, they do have plenty of other material collected from Mongolia to sort through and perhaps find similar early bony fish.

And if further evidence supports an early evolution of endochondral bone, it could point to a more interesting history for the evolution of sharks.

Dr Brazeau said: “If sharks had bony skeletons and lost it, it could be an evolutionary adaptation. Sharks don’t have swim bladders, which evolved later in bony fish, but a lighter skeleton would have helped them be more mobile in the water and swim at different depths.

“This may be what helped sharks to be one of the first global fish species, spreading out into oceans around the world 400 million years ago.”

Prehistoric big shark Megalodon, how big?

From the University of Bristol in England:

True size of prehistoric mega-shark finally revealed

September 3, 2020

To date only the length of the legendary giant shark Megalodon had been estimated. But now, a new study led by the University of Bristol and Swansea University has revealed the size of the rest of its body, including fins that are as large as an adult human.

There is a grim fascination in determining the size of the largest sharks, but this can be difficult for fossil forms where teeth are often all that remain.

Today, the most fearsome living shark is the Great White, at over six metres (20 feet) long, which bites with a force of two tonnes.

Its fossil relative, the big tooth shark Megalodon, star of Hollywood movies, lived from 23 to around three million years ago, was over twice the length of a Great White and had a bite force of more than ten tonnes.

The fossils of the Megalodon are mostly huge triangular cutting teeth bigger than a human hand.

Jack Cooper, who has just completed the MSc in Palaeobiology at the University of Bristol’s School of Earth Sciences, and colleagues from Bristol and Swansea used a number of mathematical methods to pin down the size and proportions of this monster, by making close comparisons to a diversity of living relatives with ecological and physiological similarities to Megalodon.

The project was supervised by shark expert Dr Catalina Pimiento from Swansea University and Professor Mike Benton, a palaeontologist at Bristol. Dr Humberto Ferrón of Bristol also collaborated.

Their findings are published today in the journal Scientific Reports.

Jack Cooper said: “I have always been mad about sharks. As an undergraduate, I have worked and dived with Great whites in South Africa — protected by a steel cage of course. It’s that sense of danger, but also that sharks are such beautiful and well-adapted animals, that makes them so attractive to study.

“Megalodon was actually the very animal that inspired me to pursue palaeontology in the first place at just six years old, so I was over the moon to get a chance to study it.

“This was my dream project. But to study the whole animal is difficult considering that all we really have are lots of isolated teeth.”

Previously the fossil shark, known formally as Otodus megalodon, was only compared with the Great White. Jack and his colleagues, for the first time, expanded this analysis to include five modern sharks.

Dr Pimiento said: “Megalodon is not a direct ancestor of the Great White but is equally related to other macropredatory sharks such as the Makos, Salmon shark and Porbeagle shark, as well as the Great white. We pooled detailed measurements of all five to make predictions about Megalodon.”

Professor Benton added: “Before we could do anything, we had to test whether these five modern sharks changed proportions as they grew up. If, for example, they had been like humans, where babies have big heads and short legs, we would have had some difficulties in projecting the adult proportions for such a huge extinct shark.

“But we were surprised, and relieved, to discover that in fact that the babies of all these modern predatory sharks start out as little adults, and they don’t change in proportion as they get larger.”

Jack Cooper said: “This means we could simply take the growth curves of the five modern forms and project the overall shape as they get larger and larger — right up to a body length of 16 metres.”

The results suggest that a 16-metre-long Otodus megalodon likely had a head round 4.65 metres long, a dorsal fin approximately 1.62 metres tall and a tail around 3.85 metres high.

This means an adult human could stand on the back of this shark and would be about the same height as the dorsal fin.

The reconstruction of the size of Megalodon body parts represents a fundamental step towards a better understanding of the physiology of this giant, and the intrinsic factors that may have made it prone to extinction.

Sea angels, sharks or rays?

This April 2020 video from California in the USA is called Angel Shark Quest | JONATHAN BIRD’S BLUE WORLD.

From the University of Vienna in Austria:

Between shark and ray: The evolutionary advantage of the sea angels

Threatened with extinction despite perfect adaptation

August 4, 2020

Summary: Angel sharks are sharks, but with their peculiarly flat body they rather resemble rays. An international research team has now investigated the origin of this body shape. The results illustrate how these sharks evolved into highly specialized, exclusively bottom-dwelling ambush predators and thus also contribute to a better understanding of their threat from environmental changes

The general picture of a shark is that of a fast and large ocean predator. Some species, however, question this image — for example angel sharks. They have adapted to a life on the bottom of the oceans, where they lie in wait for their prey. In order to be able to hide on or in the sediment, the body of angel sharks became flattened in the course of their evolution, making them very similar to rays, which are closely related to sharks.

Flattened body as indication for a successful lifestyle

The oldest known complete fossils of angel sharks are about 160 million years old and demonstrate that the flattened body was established early in their evolution. This also indicates that these extinct angel sharks already had a similar lifestyle as their extant relatives — and that this lifestyle obviously was very successful.

Angel sharks are found all over the world today, ranging from temperate to tropical seas, but most of these species are threatened. In order to understand the patterns and processes that led to their present low diversity and the possible consequences of their particular anatomy, the team has studied the body shapes of angel sharks since their origins using modern methods.

Today’s species are very similar

For this purpose, the skulls of extinct species from the late Jurassic period (about 160 million years ago) and of present-day species were quantitatively analysed using X-ray and CT images and prepared skulls employing geometric-morphometric approaches. In doing so, the evolution of body shapes could be explained comparatively, independent of body size.

The results show that early angel sharks were different in their external shape, whereas modern species show a comparably lower variation in shape. “Many of the living species are difficult to identify on the basis of their skeletal anatomy and shape, which could be problematic for species recognition,” explains Faviel A. López-Romero.

Angel sharks are well adapted, but react slowly to environmental changes

It has been shown that in living species the individual parts of the skull skeleton are more closely integrated than in their extinct relatives. This led to a reduced variability in appearance during the evolution of angel sharks. “The effect of integrating different parts of the skull into individual, highly interdependent modules can lead to a limited ability to evolve in different forms, but at the same time increases the ability to successfully adapt to specific environmental conditions,” explains Jürgen Kriwet.

In the case of the angel sharks, increasing geographical isolation resulted in the development of different species with very similar adaptations. “But modular integration also means that such animals are no longer able to react quickly to environmental changes, which increases their risk of extinction,” concludes Jürgen Kriwet.

Bad sharks news

This July 2019 video says about itself:

Sharks 101 | National Geographic

Sharks can rouse fear and awe like no other creature in the sea. Find out about the world’s biggest and fastest sharks, how sharks reproduce, and how some species are at risk of extinction.

From the University of Exeter in Engeland, 22 July 2020:

Microplastics have been found in the guts of sharks that live near the seabed off the UK coast.

University of Exeter scientists studied four species of demersal (seabed-dwelling) shark.

Of the 46 sharks examined, 67% contained microplastics and other human-made fibres.

From James Cook University in Australia, 22 July 2020:

A massive global study of the world’s reefs has found sharks are ‘functionally extinct’ on nearly one in five of the reefs surveyed.

Professor Colin Simpfendorfer from James Cook University in Australia was one of the scientists who took part in the study, published today in Nature by the Global FinPrint organisation. He said of the 371 reefs surveyed in 58 countries, sharks were rarely seen on close to 20 percent of those reefs.

How tiger sharks travel, new research

This 2018 video is called Tiger shark face-off.

From Florida Atlantic University in the USA:

Study first to show tiger sharks’ travels and desired hangouts in the Gulf of Mexico

Using satellite telemetry, FAU Harbor Branch scientist and team document core habitat use

July 15, 2020

Summary: From 2010 to 2018, scientists tagged 56 tiger sharks of varying life stages to track their movements via satellite. Movement patterns varied by life stage, sex, and season. Some of their core habitats overlapped with locations designated by NOAA as Habitat Areas of Particular Concern and also were found near 2,504 oil and gas platforms. Findings may help inform studies into potential climate change, oil spills, and other environmental impacts on tiger shark movement in the Gulf of Mexico.

Like other highly migratory sharks, tiger sharks (Galeocerdo cuvier) often traverse regional, national and international boundaries where they encounter various environmental and human-made stressors. Their range and habitat use in the Gulf of Mexico, a complex marine environment significantly impacted by the Deepwater Horizon Oil Spill in 2010, has been understudied and remains unknown.

Using sophisticated satellite telemetry, a study is the first to provide unique insights into how tiger sharks move and use habitats in the Gulf of Mexico across life-stages. Data from the study, just published in PLOS ONE, provide an important baseline for comparison against, and/or predicting their vulnerability to future environmental change such as climate variability or oil spills.

For the study, Matt Ajemian, Ph.D., lead author and an assistant research professor at Florida Atlantic University’s Harbor Branch Oceanographic Institute, and a team of scientists examined size and sex-related movement and distribution patterns of tiger sharks in the Gulf of Mexico. They fitted 56 tiger sharks with Smart Position and temperature transmitting tags between 2010 — following the Deepwater Horizon Oil Spill — and 2018 — spanning shelf waters from south Texas to south Florida and examined seasonal and spatial distribution patterns across the Gulf of Mexico. The tags transmitted whenever the fin-mounted tags broke the sea surface, with orbiting satellites estimating shark positions based on these transmissions. Ajemian also analyzed overlap of core habitats among individuals relative to large benthic features including oil and gas platforms, natural banks, and bathymetric breaks.

“While all life stages of tiger sharks are known to occur in the Gulf of Mexico, detailed habitat use has never been quantified,” said Ajemian. “This is rather striking as this marine system faces numerous human-madeResults showed significant ontogenetic and seasonal differences in distribution patterns as well as across-shelf stressors, complex tri-national management, and indications of size reductions in recreational landings for large sharks.”

Results showed significant ontogenetic and seasonal differences in distribution patterns as well as across-shelf (i.e., regional) and sex-linked variability in movement rates. Prior studies into tiger shark horizontal movements in the western North Atlantic Ocean have been restricted primarily to males or females separately, in disparate locations. By simultaneously tracking many males and females of varying life stages within the same region, the researchers observed sex and size-specific differences in distribution and movement rates, as well as associations with large-scale habitat features. For example, researchers found evidence of tiger shark core regions encompassing the National Oceanographic and Atmospheric Administration designated Habitat Areas of Particular Concern during cooler months, particularly by females. These are specifically bottom features of the Gulf that rise up from the edges of the continental shelf, and include places like the Flower Garden Banks National Marine Sanctuary. Additionally, shark core regions intersected with 2,504 oil and gas platforms, where previous researchers have observed them along the bottom.

Results showed significant ontogenetic and seasonal differences in distribution patterns as well as across-shelf (i.e., regional) and sex-linked variability in movement rates. Prior studies into tiger shark horizontal movements in the western North Atlantic Ocean have been restricted primarily to males or females separately, in disparate locations. By simultaneously tracking many males and females of varying life stages within the same region, the researchers observed sex and size-specific differences in distribution and movement rates, as well as associations with large-scale habitat features. For example, researchers found evidence of tiger shark core regions encompassing the National Oceanographic and Atmospheric Administration designated Habitat Areas of Particular Concern during cooler months, particularly by females. These are specifically bottom features of the Gulf that rise up from the edges of the continental shelf, and include places like the Flower Garden Banks National Marine Sanctuary. Additionally, shark core regions intersected with 2,504 oil and gas platforms, where previous researchers have observed them along the bottom.

The scientists note that future research may benefit from combining alternative tracking tools, such as acoustic telemetry and genetic approaches, which can facilitate long-term assessment of tiger shark movement dynamics and help identify the role of the core habitats identified in this study.

“This research is just a first glimpse into how these iconic predators use the Gulf of Mexico’s large marine ecosystem,” said Ajemian.

Nine walking shark species discovered

This 20 June 2020 video says about itself:

Scientists have discovered 9 species of ‘walking’ sharks.

In US news and current events today, researchers have confirmed that walking sharks branched from their nearest ancestor 9 million years ago, making them the most recently evolved type of shark. These sharks, who use their fins to ‘walk’ on the ocean floor, have been found off the coasts of Australia, Indonesia & New Guinea. Scientists have discovered a total of 9 species of walking sharks over the past 2 decades.

Read more here.

New shark species discovered off Japan

From ScienceDaily:

A new character for Pokémon? Novel endemic dogfish shark species discovered from Japan

June 11, 2020

Summary: A new endemic deep-water dogfish shark: Squalus shiraii, was discovered in the tropical waters of Southern Japan by an international team of scientists. The finding brings the amount of spurdog shark species inhabiting Japanese waters to six.

Newly discovered creatures can often be as impressive and exciting as the ones from the Japanese movies and shows. Many of those fictional characters, including inhabitants of the famous Pokémon universe, might have their analogues among the real animals native to Japan. Maybe, a new species of the dogfish shark published in the open-access journal Zoosystematics and Evolution is also “a real Pokémon” to be?

A new deep-water dogfish shark: Squalus shiraii, was discovered in the tropical waters of Southern Japan by an international team of scientists, led by Dr. Sarah Viana from South African Institute for Aquatic Biodiversity.

The new shark has the body length of 59-77 cm and some unique characteristics such as tall first dorsal fin and caudal fin with broad white margins. Currently, the species is known exclusively as a Japanese endemic, occurring in the tropical shallow waters of Southern Japan in the North-western Pacific.

Spurdogs are commercially important for the world fish trade taxa. They are caught for a range of purposes: consumption of meat, fins and liver oil. Despite their high occurrence, the accurate identification data of species is scarce, population threats and trends remain unknown.

Japan currently represents one of the world’s leading shark fish trade countries, though, during the last decades the amount of shark catches is decreasing and over 78 elasmobranch species traded in Japanese shark fin markets are now evaluated as threatened.

The new species Squalus shiraii previously used to be massively misidentified with shortspine spurdog, due to the resembling shape of body, fins and snout length. However, there are some differences, defining the specificity of the new species.

“Squalus shiraii has body brown in colour, postventral and preventral caudal margins whitish, dorsal and ventral caudal tips broadly white and black upper caudal blotch evident in adults. S. mitsukurii has body conspicuously black to dark grey and caudal fins black throughout with post-ventral caudal margin fairly whitish and black upper caudal blotch not evident in adults,” shares lead author Dr. Viana.

Scientists propose the name for the newly described species as Shirai’s spurdog in honor to Dr. Shigeru Shirai, the former Japanese expert of the group.

Swimming with whale sharks

This 19 May 2020 BBC video says about itself:

Swim With The Biggest Fish In The Ocean | VR 360 | Seven Worlds, One Planet

Whale sharks share the fishermen’s catch in the seas of Indonesia. These gentle giants were once hunted and killed, but here their numbers are on the rise thanks to this special relationship. Stay in and explore their underwater world.

First fossil great white shark nursery discovered

This September 2014 video says about itself:

Scientists discover a great white shark pupping ground in the Sea of Cortez.

From the University of Vienna in Austria:

First fossil nursery of the great white shark discovered

Paleo-kindergarten ensured evolutionary success millions of years ago

May 22, 2020

Summary: An international research team discovered the first fossil nursery area of the great white shark, Carcharodon carcharias in Chile. This discovery provides a better understanding of the evolutionary success of the largest top predator in today’s oceans in the past and could contribute to the protection of these endangered animals.

The great white shark is one of the most charismatic, but also one of the most infamous sharks. Despite its importance as top predator in marine ecosystems, it is considered threatened with extinction; its very slow growth and late reproduction with only few offspring are — in addition to anthropogenic reasons — responsible for this.

Young white sharks are born in designated breeding areas, where they are protected from other predators until they are large enough not to fear competitors any more. Such nurseries are essential for maintaining stable and sustainable breeding population sizes, have a direct influence on the spatial distribution of populations and ensure the survival and evolutionary success of species. Researchers have therefore intensified the search for such nurseries in recent years in order to mitigate current population declines of sharks by suitable protection measures. “Our knowledge about current breeding grounds of the great white shark is still very limited, however, and palaeo-nurseries are completely unknown,” explains Jaime Villafaña from the University of Vienna.

He and his colleagues analysed statistically 5 to 2 million-year-old fossil teeth of this fascinating shark, which were found at several sites along the Pacific coast of Chile and Peru, to reconstruct body size distribution patterns of great white shark in the past. The results show that body sizes varied considerably along the South American paleo-Pacific coast. One of these localities in northern Chile, Coquimbo, revealed the highest percentage of young sharks, the lowest percentage of “teenagers.” Sexually mature animals were completely absent.

This first undoubted paleo-nursery of the Great White Shark is of enormous importance. It comes from a time when the climate was much warmer than today, so that this time can be considered analogous to the expected global warming trends in the future. “If we understand the past, it will enable us to take appropriate protective measures today to ensure the survival of this top predator, which is of utmost importance for ecosystems,” explains palaeobiologist Jürgen Kriwet: “Our results indicate that rising sea surface temperatures will change the distribution of fish in temperate zones and shift these important breeding grounds in the future.”

This would have a direct impact on population dynamics of the great white shark and would also affect its evolutionary success in the future. “Studies of past and present nursery grounds and their response to temperature and paleo-oceanographic changes are essential to protect such ecological key species,” concluded Jürgen Kriwet.