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.

How steelhead trout build their nests


This January 2020 video from Oregon in the USA says about itself:

The Guardian Who Stands Watch For North Umpqua Steelhead

There was a time not long ago when poachers came to Steamboat Creek along the North Umpqua River and dropped sticks of dynamite into pools filled with hundreds of steelhead. Then, a man named Lee Spencer started spending every day there — to watch the fish and keep poachers at bay.

From the GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre in Germany:

Eavesdropping on trout building their nests

Seismic sensors can record signals produced by fish building spawning pits

July 28, 2020

Steelhead trout (Oncorhynchus mykiss) stir up the sediment of the river bed when building their spawning pits, thus influencing the composition of the river bed and the transport of sediment. Until now, this process could only be studied visually, irregularly and with great effort in the natural environment of the fish. Now, researchers led by Michael Dietze of the GFZ German Research Centre for Geosciences in Potsdam have used seismic sensors (geophones) to analyze the trout’s nest-building process in detail. The study was published in the journal Earth Surface Processes and Landforms.

To lay their eggs, trout use their caudal fins to dig pits up to three metres long on each side and ten centimetres deep into the river bed. The aim of the researchers was to locate these spawning pits and to analyze the chronological sequence of the construction process. To this end, the researchers set up a network of seismic stations on a 150-meter section of the Mashel River in the US state of Washington. The geophones embedded in the earth are highly sensitive and detect the slightest vibrations in the ground. Small stones moved by the fish caused short frequency pulses in the range of 20 to 100 hertz and could be distinguished from background frequencies of flowing water, raindrops and even the pulses of passing airplanes. “The same signal arrives at each of the stations slightly delayed. This enabled us to determine where the seismic wave was generated,” says Dietze, first author of the study.

The researchers listened to the construction of four spawning pits for almost four weeks from the end of April to the end of May. The geophones revealed that the trout were mostly busy building their nests within eleven days of the measurement period. The fish preferably started at sunrise and were active until early noon, followed by another period in the early evening. The trout dug in the sediment for between one and twenty minutes, typically at two- to three-minute intervals with 50 to 100 tail strokes. This was followed by a break of about the same length.

“Normally, the nest-building behaviour of the trout was recorded only very irregularly, at most weekly. We can now resolve this to the millisecond. In the future, we want to extend the method to the behaviour of other species, for example animals that dig along the banks and destabilize them,” explains Dietze. The new measurement method might support fish and behavioural biology and provide a more accurate picture of the biotic and abiotic contribution of sediment transport in rivers. “Fish can move as much sediment as a normal spring flood. The biological component can therefore play a very important role,” said Dietze.

Locally extinct fish back in the Netherlands


This 28 July 2020 Dutch video is about a rare fish species, the allis shad.

It had been considered extinct in the Netherlands, because of pollution, overfishing, and human-made obstacles in rivers had stopped its migration from the North Sea up the river Rhine.

Recently, a small opening was made in the Haringvliet dam, to enable fish to travel up the Rhine.

This week, researchers discovered two adult allis shad fish in the Haringvliet.

Lahontan Cutthroat Trout in Nevada, USA


This video from the USA says about itself:

The Pyramid Lake Lahontan Cutthroat Trout was declared extinct in the 1940’s as a result of a badly planned diversion dam on the Truckee River. Built with no consideration of the downstream Indigenous Peoples of the Pyramid Lake Paiute Tribe and their cherished homeland, the dam desiccated the lake and destroyed the habitat of its native fish. However, the fish made a near-impossible return, aided by the efforts of biologists, tribal litigators, and a carpenter.

This documentary was completed as part of a graduate study in media innovation at the University of Nevada, Reno. It premiered at the Wild and Scenic Film Festival in Nevada City, California in January of 2019.

From the University of Nevada, Reno in the USA:

Lahontan Cutthroat Trout thrive at Paiute’s Summit Lake in far northern Nevada

July 22, 2020

Summit Lake in remote northwest Nevada is home to the only self-sustaining, robust, lake population of Lahontan Cutthroat Trout, North America’s largest freshwater native trout species. Research to understand the reasons why this population continues to thrive, where others have not, will be used to protect the fish and its habitat — as well as to apply the knowledge to help restore other Nevada lakes that once had bountiful numbers of the iconic fish that historically reached 60 pounds.

A team of researchers from the University of Nevada, Reno and the Summit Lake Paiute Tribe has been studying the watershed ecosystem and recently authored two papers published in scientific journals describing their findings about the relatively small desert terminal lake.

This project is part of a 9-year collaboration to conserve habitats and promote a healthy ecosystem for the lake. University researchers Sudeep Chandra and Zeb Hogan — as well as students from their aquatics ecosystems lab and Global Water Center — work with the tribe’s Natural Resources Department, formerly led by fish biologist William Cowan before he retired from the U.S. Fish and Wildlife Service.

“An objective to implement holistic management at Summit Lake is to blend science with traditional knowledge to protect and conserve natural ecologic processes, species diversity and tribal cultural practices,” Cowan said. “The partnership with the Global Water Center, as well as many other researchers, agencies, and organizations has complemented this objective by implementing science-based research and technological advances to investigate the viability of trout in the Summit Lake watershed.”

Monitoring data, including climate, hydrology, fish and wildlife population trends and habitat integrity, is used to develop, revise or validate the tribe’s management plans and regulations. This approach is a stark contrast to when the lake ecosystem and associated resources were at risk of irreversible impacts caused by non-point source pollution, irrigation diversions, livestock grazing, and the unknown affects caused by exporting trout eggs for establishment or supplementation of other populations.

“Our team at the University wants to support the efforts initiated by the Summit Lake Tribe,” Chandra, a professor in the College of Science, said. “Our goals are to assist them in developing their science-based program to protect Nevada’s only strong, self-sustaining lake population of Lahontan Cutthroat Trout. We believe that investigations in this robust ecosystem like Summit, where there is little human impact, could improve recovery efforts in other lake systems that are less fortunate and that have lost their trout like the Walker and Tahoe. Surprisingly there are still few comparative investigations of these lake ecosystems and how they could support trout during a time for increasing global changes.”

The Lahontan Cutthroat Trout, with its crimson red-orange slash marks on the throat under the jaw and black spots scattered over steel gray to olive green scales, is Nevada’s state fish and holds a cultural significance to the Summit Lake Paiute Tribe while providing the tribe with bountiful food and fish resources.

As an important traditional food source, Lahontan Cutthroat Trout composed a large part of Tribal member’s diets and were the focus of many gatherings held to honor the fish and to learn oral history, traditional practices, and cultural resources from elders of the tribe.

“The tribe has exercised their sovereignty to protect, manage and enhance tribal homelands, including the lake ecosystem and associated resources by working with federal agencies and other organizations that enable the tribe to holistically manage and protect the land, water and resources that fish, wildlife and tribal members depend on for survival,” Cowan said.

Climate Change, drought impacts watershed

The lake is about one square mile of surface area, has a mean depth of 20 feet with the southern end generally deeper with about 50 feet of depth at the deepest. The lake elevation decreased about 13 feet during the severe drought in the western United States that lasted from 2012 to 2016.

“One thing we learned is that the climatically induced drought can change the hydrology, or flow of water and connections of stream to lake, but even with these changes, the trout populations remain relatively stable in the lake,” Chandra said. “They look for the opportunity to spawn every year and likely wait for better conditions with higher flows for better access to upstream spawning grounds.

“So it is critical to support the tribe’s efforts to protect the watershed and understand how the long term changes in water resources, like the flow of water, will change with pending climate change projections for the Great Basin.”

James Simmons, doctoral student with the Ecology, Evolution and Conservation Biology program at the University said the population appears resilient to today’s climate disturbances/drought, which is very positive, but should the frequency and severity of drought increase in the future, will the population remain resilient in the face of continued low abundance, survival, spawners and a skewed sex ratio.

“I think the key going forward will be for the tribe to try to understand how the long-term flow of water in the watershed will be impacted by the future changing climate in the Great Basin — so that the tribe can formulate a game plan to get ahead of any potential negative repercussions,” he said. “Like cutthroat populations across the western U.S., this population faces unknown impacts from climate change.

“Declining abundance and diverging male and female abundance under changing drought cycles and conditions may have negative long term consequences. The prediction of increased frequency, severity and duration of drought and an increased percentage of rain may decrease abundance, reduce the effective population size and skew the sex ratio at Summit Lake.”

The research team found that connections between the upper watershed and the lake are essential for maintaining a healthy population during a drought. During the drought of 2012-2016, Summit Lake had a strong, stable population of naturally reproducing Lahontan Cutthroat Trout. The numbers of trout spawning up Mahogany Creek, one of the lake’s only inflow streams, was also relatively stable in number. Some of the trout in the lake migrated all the way to the upper watershed, about eight miles.

“Lahontan Cutthroat Trout can live in streams and lakes,” Chandra said. “The trout that live in lakes need rivers to spawn to keep their populations healthy. The numbers do show with little to no major changes to the watershed by human development, there is still a highly variable amount of spawning from lake to stream.”

Stream flow studied

Adequate stream flow is necessary for spawning and movement to the lake-dwelling component of the population. In rivers where flow is regulated, enough flow must be preserved in the spring to allow “lake spawners” to come upstream and in the fall to allow juveniles to migrate to the lake.

“Healthy habitat and ecological connectivity between habitats, such as no man-made migration barriers and adequate stream flow, should be preserved throughout as much of the watershed as possible (and of course between the stream and the lake) to facilitate movement for both stream- and lake-dwelling fish, and to support a robust overall population,” Teresa Campbell, a biologist and staff researcher in the University’s Global Water Center and lead author of one of the scientific papers, said.

“Strong connectivity between healthy stream and lake habitats is crucially important to the long-term survival of the Summit Lake Lahontan Cutthroat Trout because it seems that the exchange of individual fish across habitats contributes to the resilience and vitality of the population as a whole.”

The study also found that in drought-prone systems, streams should have adequate pool habitat and cover such as trees and woody debris to provide a refuge area from the drought and cooler temperatures for trout.

“During the drought, in the stream, these refuge pools with structure in the form of wood, cobbles, or boulders supported higher densities of stream-dwelling trout,” Campbell said. “Therefore, this habitat type is an important component of healthy stream habitat for trout.”

Forward thinking on the part of the tribe led to early habitat protections for the stream and the lake that now contribute to the success of this population. The tribe took measures to protect much of the stream habitat, erecting grazing enclosures in the 70s that prevented cattle from trampling the stream and allowed the stream to recover into the healthy habitat it is now. This is one of the reasons that trout are thriving here.

“The lake and surface water on the Reservation are further protected by restricting public access and monitoring resources necessary to sustain endemic species diversity in the area,” Cowan said.

The Summit Lake Paiute Tribe Reservation is the most remote Native American reservation in Nevada. Located in the northwest corner of Nevada, the reservation is 50 miles south of the Oregon border and 70 miles east of the California border.

Whitespotted eagle rays’ behavior, new research


This 26 October 2018 video from the USA says about itself:

Off the coast of Sarasota, Florida, lives the spotted eagle ray—a beautiful, yet mysterious, sea creature. Very little is known about the eagle ray, so research teams from Florida Atlantic University and Mote Marine Lab are pioneering new techniques to better understand them. Along with tagging the rays to track their movements, the team records and analyzes the sounds the rays make when they eat. These new research methods could shed light on the rays’ eating habits and give researchers a deeper understanding of the animal, and, by extension, the ocean as a whole.

Join wildlife biologist Wes Larson on a mission across the United States to find the next generation of conservationists.

From Florida Atlantic University in the USA:

Biotelemetry provides unique glimpse into whitespotted eagle rays’ behavior

Ecology of this ‘near threatened’ species in Florida

July 22, 2020

Summary: Researchers are the first to characterize the ecology and fine-scale habitat use of ‘near threatened’ white-spotted eagle rays in Florida while also identifying areas of potential interactions between this species and multiple environmental threats. Biotelemetry provided unique insights into this species’ occupancy, which is not apparent at the landscape-scale. Prolonged observations showed affinities for habitats of considerable recreational and commercial importance, like inlets, channels, and clam aquaculture lease sites close to shore.

The whitespotted eagle ray (Aetobatus narinari), found in estuaries and lagoons throughout Florida, is listed as “near threatened” on the International Union for Conservation of Nature’s “Red List of Threatened Species.” Keeping tabs on this highly mobile species for conservation efforts can be extremely challenging, especially for extended periods of time.

Researchers from Florida Atlantic University’s Harbor Branch Oceanographic Institute used uniquely coded transmitters and acoustic telemetry to give them a leading edge to unravel fine-scale movement, behavior, and habitat use of whitespotted eagle rays in Florida’s Indian River Lagoon. Biotelemetry provided the researchers with unique insights into this species’ occupancy, which is not apparent at the landscape-scale.

Despite being a state-protected species in Florida for more than two decades, this study is the first to characterize the ecology and fine-scale habitat use of whitespotted rays in Florida while also identifying areas of potential interactions between this species and multiple environmental threats. For the study, researchers followed seven mature individuals (six males and one female) and individually tracked them for a total of 119.6 hours. They used a tracking vessel to continuously and manually track the rays between June 2017 and August 2018.

Results of the study, published in the journal Endangered Species Research, show that rays use the deeper portions of the Indian River Lagoon, along Florida’s southeast coast, during the day and shallower portions during the night. In addition, they move faster while in the ocean and lagoonal habitats and slower in channels and inlets. This information suggests that whitespotted eagle rays may spend more time foraging at night in the shallow water of the lagoon than during the daytime. These prolonged observations revealed affinities for habitats of considerable recreational and commercial importance, such as inlets, channels, and clam aquaculture lease sites close to shore.

“Understanding channel use is crucial to evaluating risks and potentially developing strategies to mitigate negative impacts to the whitespotted eagle ray, as both channel and inlet habitats have high levels of human activity such as boating and fishing and are prone to coastal development impacts from dredging,” said Breanna DeGroot, M.S., lead author, research technician and former graduate student working with Matt Ajemian, Ph.D., co-author and an assistant research professor at FAU’s Harbor Branch. “In addition, these high traffic areas experience increased noise and chemical pollution.”

Rays also spent a larger proportion of time in the channels and inlet during the lighter and warmer portions of the day and used shallower depths during the cooler and darker portions of the day. Rate of movement significantly increased with temperature, suggesting that rays are more active during warmer periods. While previous studies have found that whitespotted eagle rays are influenced by tidal cycles, this study did not find any tidal patterns in ray habitat use or distribution.

Because more clammers work on lease sites during the day, interactions between the rays and growout sites may therefore be underestimated. Findings from this study will help to inform statewide conservation plans for the species and provide critical information to hard clam aquaculture farmers and restoration managers for the successful production of bivalves in the area.

“As coastal populations and development increase, there is more potential for whitespotted eagle rays to interact with human activities,” said Ajemian. “In addition, intense coastal development such as dredging, construction, and pollution have been linked to habitat alteration, which may change the abundance and distribution of this species as has been documented with shark species in degraded habitats.”

As whitespotted eagle rays already display an affinity for these modified habitats, increased interactions with humans and added pollution and/or disturbances could result in changes to the species’ movement patterns and health. Ultimately, such human-induced habitat alterations could reduce the overall productivity of estuarine areas and, with time, exacerbate pressures already facing populations of aetobatid rays.

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.

Machismo not good for cichlid fish


This 2013 video says about itself:

Astatotilapia burtoni (mouthbreeder).

Astatotilapia burtoni incubating fish eggs.

New study by researchers from the University of Konstanz, the co-located Max Planck Institute of Animal Behavior (both in Germany) and the University of Texas at Austin finds that groups led by subordinate males outperform those led by dominant and aggressive males

Being the strongest, biggest and most aggressive individual in a group might make you dominant, but it doesn’t mean you make all the decisions.

A new study of fish behaviour published in the Proceedings of the National Academy of Sciences shows that dominant individuals can influence a group through force, but passive individuals are far better at bringing a group to consensus. The study, published by an international team from the Max Planck Institute of Animal Behavior, the University of Konstanz and the University of Texas at Austin, overturns assumptions that dominant individuals also have the greatest influence on their groups, and sheds light on the potential of domineering individuals to obstruct effective communication in organisations.

“The same traits that make you powerful in one context can actively reduce your influence in others, especially contexts in which individuals are free to choose who to follow,” says senior author Alex Jordan, a group leader at the Max Planck Institute of Animal Behavior and at the University of Konstanz’s Cluster of Excellence “Centre for the Advanced Study of Collective Behaviour.”

“Dominant individuals can force their will on the group by being pushy, but that also makes them socially aversive. When it comes to bringing peers to consensus during more sophisticated tasks, it is the least aggressive individuals that exert the greatest influence. Our results illustrate that although domineering individuals most often ascend to positions of power, they can in fact create the least effective influence structures at the same time.”

Separating dominance and influence

To disentangle the effects of dominance and influence, the researchers studied groups of a social cichlid fish, Astatotilpia burtoni. “This species form groups with strict social hierarchies, in which dominant males control resources, territory, and space,” says Mariana Rodriguez-Santiago, co-first author on the study and a doctoral student in the lab of co-corresponding author Hans Hofmann at UT Austin.

“We ask if the colourful dominant males, which are aggressive, central in their social networks, and control resources, are most influential? Or if drab subordinate males wield the greatest influence, despite being passive, non-territorial, and having little or no control over resources.”

The researchers separated the effects of social dominance from social influence by examining how information flows between either dominant or subordinate males and their groups in two different contexts: routine social behaviour, or a more complex social learning task. In the more complex social learning task, dominant or subordinate male fish were trained that a certain coloured light on one side of the tank meant food would soon arrive at that location. These “informed” individuals were then placed into new groups of uninformed individuals and researchers asked which group — those with informed dominant or subordinate males — more quickly learned to associate a coloured light with food.

The cost of being domineering

The researchers observed the movement of the fish and found that in routine social interactions the dominant males exerted the greatest influential by chasing and pushing the group around. But in the more complex task, where influence was not forced on the group, but rather individuals had a choice about who to follow, it was subordinate males who wielded the greatest influence in their social groups. In groups with a subordinate male as demonstrator, fish quickly came to a consensus about which light to follow, moving together as a coherent unit to succeed in the task. With a dominant male as the informant, groups were far slower to reach consensus, if they did at all.

Breaking down behaviour with machine learning

By using additional machine-learning based animal tracking, employing cutting edge techniques developed in the computer sciences, researchers were able to break down the behavioural differences between dominant and subordinate males: dominant males were central in behavioural social networks (they frequently interacted with others) but they occupied peripheral locations in spatial networks (they were avoided by others). The technology provided insights never before available, revealing the mechanisms of influence as well as the outcome.

“By capturing behavioural data that are impossible to be measured with the naked eye, our automated tracking methods revealed that it was not the difference in social position between dominant and subordinate per se, but rather in the way they moved and interacted with others,” says co-first author Paul Nührenberg, a doctoral student at the Cluster of Excellence “Centre for the Advanced Study of Collective Behaviour” at the University of Konstanz. “These behavioural differences lead directly to differences in social influence.”

Rethinking leadership

This result touches on the evolution of animal societies as well as leadership structures in organisations. “In many societies, whether animal or human, individuals in positions of power all possess a similar suite of traits, which are aggression, intimidation and coercion,” says Jordan. “But effective communication requires the presence of a diversity of voices, not just the loudest. Our results from a natural system show that allowing alternative pathways to positions of power may be useful in creating stronger advisory, governmental, and educational structures.”

Background

  • A new study of fish behaviour conducted by researchers from the University of Konstanz, the co-located Max Planck Institute of Animal Behavior and the University of Texas at Austin shows that dominant individuals can influence a group through force, but passive individuals are far better at bringing a group to consensus.
  • Using the social cichlid, Astatotilpia burtoni, which forms strict social hierarchies of dominant and subordinate males, the study separated the effects of social dominance from social influence by examining groups in two different contexts: routine social behaviour, or a more complex social learning task.
  • The study used additional machine-learning based animal tracking, employing cutting edge techniques developed in the gaming and graphics industries, to break down the behavioural differences between dominant and subordinate males.
  • Researchers include scientists from the Cluster of Excellence “Centre for the Advanced Study of Collective Behaviour” at the University of Konstanz and the co-located Max Planck Institute of Animal Behavior in Germany, and the University of Texas at Austin.
  • Funded by the National Science Foundation BEACON, the DFG Cluster of Excellence 2117 “Centre for the Advanced Study of Collective Behaviour” (ID: 422037984).

How deep-sea black fish become invisible


This video says about itself:

Deep Sea Creatures [National Geographic Documentary 2017 HD]

Deep sea creature refers to organisms that live below the photic zone of the ocean. These creatures must survive in extremely harsh conditions, such as hundreds of bars of pressure, small amounts of oxygen, very little food, no sunlight, and constant, extreme cold. Most creatures have to depend on food floating down from above.

These creatures live in very demanding environments, such as the abyssal or hadal zones, which, being thousands of meters below the surface, are almost completely devoid of light. The water is between 3 and 10 degrees Celsius and has low oxygen levels. Due to the depth, the pressure is between 20 and 1,000 bars. Creatures that live hundreds or even thousands of meters deep in the ocean have adapted to the high pressure, lack of light, and other factors.

The depths of the ocean are festooned with the most nightmarish creatures imaginable. You might think you’re safe, because these critters live thousands of feet down in a cold dark abyss, but the vampire squid, which looks like a nightmare umbrella, and the frilled shark—a literal living fossil—will live on in the recesses of your mind long after you’ve clicked away. Enjoy these deep sea horrors and try to have a relaxing day afterwards.

From Duke University in the USA:

Ultra-black skin allows some fish to lurk unseen

Packed pigment granules help them blend in without blowing their cover

July 16, 2020

Summary: Scientists report that at least 16 species of deep-sea fish have evolved ultra-black skin that absorbs more than 99.5% of the light that hits them, making them nearly impossible to pick out from the shadows. These fish owe their disappearing act to tiny packets of pigment within their skin cells called melanosomes. The melanosomes of ultra-black fish are differently shaped and arranged on a microscopic level, compared with regular black fish, says a new study.

If there were a stagehand of the sea, wearing black to disappear into the darkness backstage, it might be the dragonfish. Or the common fangtooth.

These fish live in the ocean’s inky depths where there is nowhere to take cover. Even beyond the reach of sunlight, they can still be caught in the glow of bioluminescent organisms that illuminate the water to hunt. So they evade detection with a trick of their own: stealth wear.

Scientists report that at least 16 species of deep-sea fish have evolved ultra-black skin that absorbs more than 99.5% of the light that hits them, making them nearly impossible to pick out from the shadows.

These fish owe their disappearing act to tiny packets of pigment within their skin cells called melanosomes. The melanosomes of ultra-black fish are differently shaped and arranged, on a microscopic level, compared with regular black fish, says a study led by Duke University and the Smithsonian National Museum of Natural History.

The researchers say the work could lead to new light-trapping materials for use in applications ranging from solar panels to telescopes.

For the paper, to be published July 16 in the journal Current Biology, the team used a trawl net and a remotely operated vehicle to scoop up 39 black fish swimming up to a mile deep in the waters of Monterey Bay and the Gulf of Mexico, and bring them up to a ship to study.

Using a spectrometer to measure the amount of light reflected off the fishes’ skin, the researchers identified 16 species that reflected less than 0.5% of light, making them some 20 times darker and less reflective than everyday black objects.

“Ultra-black arose more than once across the fish family tree,” said first author Alexander Davis, a biology Ph.D. student in Sonke Johnsen’s lab at Duke.

The darkest species they found, a tiny anglerfish not much longer than a golf tee, soaks up so much light that almost none — 0.04% — bounces back to the eye. Only one other group of black animals, the birds-of-paradise of Papua New Guinea with their ultra-dark plumage, are known to match them.

Getting decent photos of these fish onboard the ship was tough; their features kept getting lost. “It didn’t matter how you set up the camera or lighting — they just sucked up all the light,” said research zoologist Karen Osborn of the Smithsonian National Museum of Natural History.

The team found that, when magnified thousands of times under electron microscopes, normal black skin and ultra-black skin look very different. Both have tiny structures within their cells that contain melanin — the same pigment that lends human skin its color. What sets ultra-black fish apart, they say, is the shape and arrangement of these melanosomes.

Other cold-blooded animals with normal black skin have tiny pearl-shaped melanosomes, while ultra-black ones are larger, more tic-tac-shaped. And ultra-black skin has melanosomes that are more tightly packed together, forming a continuous sheet around the body, whereas normal black skin contains unpigmented gaps.

The researchers ran some computer models, simulating fish skin containing different sizes and shapes of melanosomes, and found that ultra-black melanosomes have the optimal geometry for swallowing light.

Melanosomes are packed into the skin cells “like a tiny gumball machine, where all of the gumballs are of just the right size and shape to trap light within the machine,” Davis said.

Their ultra-black camouflage could be the difference between eating and getting eaten, Davis says. By being blacker than black, these fish manage to avoid detection even at six-fold shorter ranges.

Helping fish to survive


This video from the Philippines says about itself:

Shallow Water Reef Dome Deployment – Dumaguete

BPI Bayan Dumaguete headed by Mr. Gary Rosales in collaboration with the Barangay Officials of Bantayan, Dumaguete City deployed 20 reef domes as artificial reefs inside a marine protected area.

June 7, 2014

Video: Mike Alano
Music: www. bensound. com

From the University of New South Wales in Australia:

Fish reef domes a boon for environment, recreational fishing

July 16, 2020

Summary: Humanmade reefs can be used in conjunction with the restoration or protection of natural habitat to increase fish abundance in estuaries, researchers have found.

In a boost for both recreational fishing and the environment, new UNSW research shows that artificial reefs can increase fish abundance in estuaries with little natural reef.

Researchers installed six humanmade reefs per estuary studied and found overall fish abundance increased up to 20 times in each reef across a two-year period.

The study, published in the Journal of Applied Ecology recently, was funded by the NSW Recreational Fishing Trust.

The research was a collaboration between UNSW Sydney, NSW Department of Primary Industries (DPI) Fisheries and the Sydney Institute of Marine Science (SIMS).

Professor Iain Suthers, of UNSW and SIMS, led the research, while UNSW alumnus Dr Heath Folpp, of NSW DPI Fisheries, was lead author.

Co-author Dr Hayden Schilling, SIMS researcher and Conjoint Associate Lecturer at UNSW, said the study was part of a larger investigation into the use of artificial reefs for recreational fisheries improvement in estuaries along Australia’s southeast coast

“Lake Macquarie, Botany Bay and St Georges Basin were chosen to install the artificial reefs because they had commercial fishing removed in 2002 and are designated specifically as recreational fishing havens,” Dr Schilling said.

“Also, these estuaries don’t have much natural reef because they are created from sand. So, we wanted to find out what would happen to fish abundance if we installed new reef habitat on bare sand.

“Previous research has been inconclusive about whether artificial reefs increased the amount of fish in an area, or if they simply attracted fish from other areas nearby.”

Fish reef domes boost abundance

In each estuary, the scientists installed 180 “Mini-Bay Reef Balls” — commercially made concrete domes with holes — divided into six artificial reefs with 30 units each.

Each unit measures 0.7m in diameter and is 0.5m tall, and rests on top of bare sand.

Professor Suthers said artificial reefs were becoming more common around the world and many were tailored to specific locations.

Since the study was completed, many more larger units — up to 1.5m in diameter — have been installed in NSW estuaries.

“Fish find the reef balls attractive compared to the bare sand: the holes provide protection for fish and help with water flowing around the reefs,” Prof Suthers said.

“We monitored fish populations for about three months before installing the reefs and then we monitored each reef one year and then two years afterwards.

“We also monitored three representative natural reef control sites in each estuary.”

Prof Suthers said the researchers observed a wide variety of fish using the artificial reefs.

“But the ones we were specifically monitoring for were the species popular with recreational fishermen: snapper, bream and tarwhine,” he said.

“These species increased up to five times and, compared to the bare sand habitat before the reefs were installed, we found up to 20 times more fish overall in those locations.

“What was really exciting was to see that on the nearby natural reefs, fish abundance went up two to five times overall.”

Dr Schilling said that importantly, their study found no evidence that fish had been attracted from neighbouring natural reefs to the artificial reefs.

“There was no evidence of declines in abundance at nearby natural reefs. To the contrary, we found abundance increased in the natural reefs and at the reef balls, suggesting that fish numbers were actually increasing in the estuary overall,” he said.

“The artificial reefs create ideal rocky habitat for juveniles — so, the fish reproduce in the ocean and then the juveniles come into the estuaries, where there is now more habitat than there used to be, enabling more fish to survive.”

The researchers acknowledged, however, that while the artificial reefs had an overall positive influence on fish abundance in estuaries with limited natural reef, there might also be species-specific effects.

For example, they cited research on yellowfin bream which showed the species favoured artificial reefs while also foraging in nearby seagrass beds in Lake Macquarie, one of the estuaries in the current study.

NSW DPI Fisheries conducted an impact assessment prior to installation to account for potential issues with using artificial reefs, including the possibility of attracting non-native species or removing soft substrate.

Artificial reef project validated

Dr Schilling said their findings provided strong evidence that purpose-built artificial reefs could be used in conjunction with the restoration or protection of existing natural habitat to increase fish abundance, for the benefit of recreational fishing and estuarine restoration of urbanised estuaries.

“Our results validate NSW Fisheries’ artificial reef program to enhance recreational fishing, which includes artificial reefs in estuarine and offshore locations,” he said.

“The artificial reefs in our study became permanent and NSW Fisheries rolled out many more in the years since we completed the study.

“About 90 per cent of the artificial reefs are still sitting there and we now have an Honours student researching the reefs’ 10-year impact.” Dr Schilling said the artificial reefs were installed between 2005 and 2007, but the research was only peer-reviewed recently.

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.