Holding sharks, how to do it


This 26 May 2019 video says about itself:

In this season 5 excerpt, Jonathan learns from master shark handler Neal Harvey how to put a shark into tonic immobility and then pick it up!

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Small fish crucial for coral reef biodiversity


This 2018 video is called The Coral Reef: 10 Hours of Relaxing Oceanscapes | BBC Earth.

From the Smithsonian Institution in the USA:

Live fast, die young: Study shows tiny fishes fuel coral reefs

May 23, 2019

Scientists have long sought to understand how coral reefs support such an abundance of fish life despite their location in nutrient-poor waters. According to a new study published May 23 in the journal Science, an unlikely group fuels these communities: tiny, mostly bottom-dwelling creatures called “cryptobenthic” reef fishes.

The study shows that these fishes perform a critical role on coral reefs, supplying almost 60% of consumed fish food by constantly replenishing their populations in a rapid cycle of life and death.

“Scientists have puzzled over coral reefs for centuries, wondering how such productive, diverse ecosystems survive in what is essentially a marine desert,” said lead author Simon Brandl, formerly with the Smithsonian’s Tennenbaum Marine Observatories Network and currently a postdoctoral research fellow with Simon Fraser University. “It’s remarkable to find that these tiny, almost universally overlooked fishes actually serve as the cornerstone of coral-reef fish communities.”

Cryptobenthic reef fishes, such as gobies, blennies or cardinalfishes, are the smallest of all marine vertebrates. Although they vary in size, the tiniest cryptobenthics will never reach 1 inch and weigh almost nothing. Other coral-reef dwellers eat these fishes in large quantities, most within the first few weeks of their existence.

Instead of disappearing, however, cryptobenthic fish populations somehow flourish in the face of constant predation. The researchers solved this paradox by studying the larvae of reef fishes. While the larvae of most fish species disperse into the open ocean, where only a few survive, cryptobenthics behave differently. Brandl and his team found that most cryptobenthic larvae appear to remain close to their parents’ reefs, yielding many more survivors among their babies. These larvae then rapidly replace cryptobenthic adults eaten on the reef, sustaining the growth of larger reef fishes.

“We found that cryptobenthic fish larvae absolutely dominate the larval-fish communities near reefs, which provides a continuous stream of new generations of tiny fish as a food source for other reef creatures,” said Carole Baldwin, co-author on the study and curator of fishes at the Smithsonian’s National Museum of Natural History. “It’s incredible that these fishes contribute so much to coral reefs. They’re so small that historically we haven’t recognized their enormous significance.”

Scientists from Australia, Canada, France and the United States contributed to this research. The team studied cryptobenthics in Belize, French Polynesia and Australia, combed decades of data on coral-reef fish larvae and developed a population model to better understand how cryptobenthics contribute to the diet of coral-reef dwellers.

The study began in 2015, when Brandl was a postdoctoral fellow at the Smithsonian’s Marine Global Earth Observatory (MarineGEO), but these tiny fishes are more relevant today than ever. As coral reefs undergo dramatic declines, their fish communities — and the people who depend on them — may be in jeopardy. The researchers hope that the vast diversity of cryptobenthics and their unique way of life can make them a resilient foundation for coral reefs.

Teaching Atlantic sturgeon to survive


This 6 May 2014 video from Virginia in the USA says about itself:

James River Association’s educational video on how the public can help take care of the river by decreasing sedimentation, which will help make sure the Atlantic Sturgeon can continue to have a great return to the James River.

From Forschungsverbund Berlin in Germany:

Threatened sturgeon learns for the fitness

May 7, 2019

An international team led by IGB is providing one of the first proofs of the complex learning behaviour of fish in a recent study. The Atlantic sturgeon is considered extinct in Germany. The IGB is coordinating the reintroduction of these up to five meter large river giants and is investigating whether sturgeon training can increase their fitness for the wild. An important fitness factor is their feeding behavior. A two-week “learning lead” made the search for food more efficient. In addition, the increased formation of the transcription factor neurod1 — an important neuronal component of learning — could be demonstrated in the brain of the trained sturgeons.

Sturgeons are among the most endangered fish species in the world. In the past, two species of these migratory fish were native to the North Sea and Baltic tributaries of Germany. The European sturgeon (Acipenser sturio) lived in the North Sea and the catchment areas of the Elbe, the Atlantic sturgeon (Acipenser oxyrinchus) settled in the Baltic Sea and the catchment areas of the Oder. The IGB develops the scientific basis for the reintroduction of these two species in Germany. This also includes stocking measures with pre-reared young fish. “We have the highest mortality rate of reintroduced sturgeons in the first days in the wild. The faster the animals adapt to the new conditions, the higher the chance of survival.With our investigations we want to create the basis to optimally prepare the animals for the reintroduction,” is how the IGB researcher and study leader, Sven Wuertz, describes the background of the study.

Little known about the learning behaviour of fish so far

Compared to mammals, the formation of nerve cells in the brain in fish is very dynamic and remains active throughout life. This enables fish to react very well to changes in their environment. So far, however, there are only few scientific findings on the underlying physiological processes of the learning behaviour in fish.

Like a vacuum cleaner, sturgeons pick up their prey from the bottom of the watercourse

In the behavioural studies, sturgeons were divided into two groups and kept in large current channels; in nature, sturgeons feed on small organisms such as insect larvae and crustaceans, which they suck up from the fine sandy bottom of the water. The “training team” had to look for food from a handful of sand in their rearing tank for two weeks in order to imitate food intake under natural conditions The group without training was given the insect larvae on the bare floor of the current channel. After two weeks, both groups had to search for their prey in a current channel with completely covered sandy soil in which the food was buried.

The training shows effect

The trained fish found the food twice as fast as their untrained conspecifics and there were also differences in the brain structure. Neurod1 is a transcription factor that is produced in greater numbers when new nerve cells are formed. It serves as an indicator for the neuronal component of learning. The gene expression of neurod1 was significantly higher in the trained animals than in the untrained ones. The complicated search for food thus caused the animals’ brains to be more active and to process learning experiences. “The results are significant from a scientific point of view, as there is little evidence to date for the complex learning behaviour of fish. From the point of view of species protection, the results are also very important: Based on the results, we can further optimize the rearing conditions for our sturgeons,” summarizes Joern Gessner, co-author of the study and coordinator of the reintroduction program.

Tropical fish off North Carolina, USA


This June 2017 video says about itself:

Sent the GoPro down on a popular Gulf of Mexico shipwreck. There was so much life including various baits (cigar minnows, spanish sardines, grunts, vermillion snapper), mangrove snapper, red snapper, grouper, goliath grouper, amberjack, barracuda, and much more!

From Duke University in the USA:

Shipwrecks off North Carolina, U.S. coast harbor tropical migrants

Artificial reefs are preferred habitat for tropical fish searching for favorable habitat

May 6, 2019

Summary: Shipwrecks and sunken structures off the North Carolina coast may act as stepping stones for tropical fish searching for favorable habitats at or beyond the edge of their normal geographic range. A study finds these fishes prefer artificial reefs over natural ones and suggests linked networks of these human-made structures could be used to aid the survival of the ecologically and economically important species.

Tropical and subtropical fish are taking up residence on shipwrecks and other sunken structures off the North Carolina coast. This pattern may continue or even accelerate in coming years given predictions of warming oceans under climate change, a new study co-led by Duke University scientists suggests.

“The artificial reefs created by these structures may be acting as stepping stones for fish that are moving northward and living at the edge of their geographic range, or beyond it, in search of suitable habitat,” said Avery B. Paxton, a visiting scholar at the Duke University Marine Laboratory, who was lead author of the study.

“Globally, there is broad evidence that many tropical fish species are shifting their ranges poleward and to deeper waters in response to changing ocean conditions, and what we see on these reefs seems to fit that pattern,” she said.

One of the most surprising findings of the study is that the tropical and subtropical fish observed off North Carolina exhibit a strong preference for hanging out on human-made structures versus natural rocky reefs found nearby, noted J. Christopher Taylor, a research ecologist at NOAA’s National Centers for Coastal Ocean Science and a co-author of the study.

“It could be that the zooplankton and smaller fish these species eat are more plentiful on artificial reefs. Or it could be that human-made reefs’ complex structures give the fish more nooks and crannies where they can evade predators. We’re still trying to figure it out,” Taylor said.

The fishes’ preference for artificial habitats suggests networks of the human-made structures — which are already commonly found up and down the East Coast and in other waters worldwide — could act as underwater corridors the fish use to reach the habitats they need to survive, said Paxton, who also works with CSS Inc. under contract to NOAA’s National Centers for Coastal Ocean Science.

Paxton, Taylor and their colleagues published their peer-reviewed paper May 6 in Nature Communications Biology.

To do the study, teams of scuba-diving scientists conducted population and species counts at 30 artificial and natural reefs off the N.C. coast between 2013 and 2015. To track seasonal differences in fish populations, most of the reefs were visited four times a year.

Analysis of the data confirmed that the number and diversity of tropical and subtropical fish on deep artificial reefs was far greater than on nearby natural reefs.

Common tropical species spotted on the artificial reefs included blue chromis, purple reef fish and bluehead wrasse. Common subtropical species spotted there included vermilion snapper, greater amberjack and bar jack.

Temperate fish species such as black sea bass and tautog, on the other hand, were far more prevalent on the area’s natural rocky reefs.

The depth of the artificial reef mattered hugely, Paxton noted.

“We didn’t see these patterns on artificial reefs at shallow or intermediate depths, we only saw them on deep reefs, located between 80 to 115 feet below the surface, where water temperatures often experience less seasonal change,” she said.

Good United States freshwater fish news


This 2017 video says about itself:

Few people realize that there are over 1,000 fish species swimming in North America’s fresh water.

From PLOS:

Freshwater fish species richness has increased in Ohio River Basin since ’60s

April 24, 2019

The taxonomic and trophic composition of freshwater fishes in the Ohio River Basin has changed significantly in recent decades, possibly due to environmental modifications related to land use and hydrology, according to a study published April 24 in the open-access journal PLOS ONE by Mark Pyron of Ball State University, and colleagues.

Human-made threats to freshwater ecosystems are numerous and globally widespread. The legacy of agriculture and land use is manifested in the Ohio River Basin, drastically modified via logging and wetland draining following European colonization. After this period, the Ohio River Basin watershed was historically dominated by agriculture, and then converted from agriculture to forest during the 1960s-80s. The effects of these changes on fish throughout the basin are not fully known.

Pyron and colleagues used 57 years of rotenone and electrofishing fish collection survey data (1957-2014), collected by the Ohio River Valley Water Sanitation Commission, to examine changes to taxonomy, trophic classifications, and life history strategies of freshwater fish assemblages in the Ohio River Basin over this period.

Annual species richness varied from 31 to 90 species and generally showed a positive trend, increasing over time. Taxonomic and trophic structure was correlated with the decrease in agriculture and increase in forest. The trophic composition of fish catch also correlated with this changes to the Basin’s hydrology. In general, the environmental modifications were associated with more fish species which feed on plant matter and detritus, and fewer fish feeding on plankton and on other fish.

The authors believe that future land use modifications, climate change, and altered biotic interactions could continue to contribute to complex patterns of change in freshwater fish assemblages in the Ohio River.

Pyron adds: “We found significant changes in species and trophic composition of freshwater fishes in the Ohio River Basin from 1957-2014. Species richness increased with year and the fish assemblages varied with changes in landuse and hydrologic alteration.”

Sand tiger sharks return to US shipwrecks


This December 2016 video from the USA says about itself:

Sand Tiger Sharks of North Carolina | JONATHAN BIRD’S BLUE WORLD

Jonathan heads to North Carolina to explore the offshore shipwrecks of the “Graveyard of the Atlantic” which have become home to Sand Tiger sharks. The sharks are unwitting bodyguards to small fish seeking protection from predators and have developed a clever way to hide from the fish and to hover with perfect buoyancy control.

JONATHAN BIRD’S BLUE WORLD is an Emmy Award-winning underwater science/adventure program that airs on public television in the United States.

From Duke University in the USA:

Sand tiger sharks return to shipwrecks off N.C. coast

Coast’s hundreds of shipwrecks are important habitats for vulnerable shark species

April 22, 2019

Summary: A study reveals shipwrecks off North Carolina’s coast are important habitats for sand tiger sharks, whose population plummeted in the 1980 and 1990s. Photos taken months and even years apart by scuba divers show female sand tiger sharks returning to the same shipwrecks. The photos were uploaded to the citizen-science program Spot A Shark USA which used specialized software to ID the sharks.

Photos taken months, and in some cases years, apart by scuba divers show female sand tiger sharks returning to the same shipwrecks off the North Carolina coast, a new study co-led by scientists at Duke University reveals.

This display of “site fidelity” by the sharks suggests the shipwrecks are important habitats for the fierce-looking but docile species, which experienced dramatic population drops toward the end of the last century and is listed as globally vulnerable by the International Union for Conservation of Nature (IUCN).

“Their population is estimated to have dropped by as much as or more than 75 percent in the 1980s and 1990s and we don’t know if it has stabilized or is still declining, in large part because we’ve mostly had to rely on anecdotal sightings,” said Avery B. Paxton, a visiting scholar at the Duke University Marine Laboratory in Beaufort, North Carolina and lead author of the study.

“Having photographic evidence that these wrecks form an important habitat the sharks return to from time to time gives us a focal point for ongoing research so we can better understand how the species is faring,” she said.

“We’re now trying to figure out why they return. They could be using the wrecks as rest stops along their migratory paths, but they could also be returning here for mating or possibly to give birth. There are all kinds of hypotheses our team is testing,” said Paxton, who formerly was a postdoctoral researcher at the South-East Zoo Alliance for Reproduction & Conservation.

She and her colleagues published their peer-reviewed paper April 22 in Ecology.

Having access to photos taken by citizen scientists, including images uploaded to the Spot A Shark USA program led by the North Carolina Aquariums, was vital to the study’s success.

“This area is called the Graveyard of the Atlantic for a reason — it has hundreds of wrecks. As researchers, we can’t have eyes underwater at each of them,” Paxton said. “Being able to rely on scuba divers and other citizen scientists who are out there and have cameras with them extends our reach.”

Each sand tiger shark has a unique pattern of brown spots on its skin that acts like a fingerprint, allowing scientists to identify individual sharks and distinguish them from others of their species.

By analyzing and comparing the spot patterns on sharks in divers’ photos dating back to 2007, Paxton and her colleagues identified six female sand tiger sharks that have returned to the same wrecks, or to similar wrecks close by, at intervals ranging from one to 72 months apart.

“This is the first time we’ve been able to document site fidelity to habitats in offshore waters along the East Coast,” Paxton said. “Previous studies have shown similar behavior patterns in Australia and Africa and in estuarine habitats such as Delaware Bay, so what we are finding off North Carolina definitely fits into global patterns.”

Male sharks may also exhibit site fidelity to wrecks off the North Carolina coast, but so far no matching photos have been found to prove it.

That may change as more and more citizen scientists share their images, said Hap Fatzinger, director of the North Carolina Aquarium at Fort Fisher and a co-author of the study.

“Through collaborations and strong partnerships, Spot A Shark USA is engaging recreational divers to become citizen scientists and provide essential data to expand our knowledge,” Fatzinger said. “By increasing community engagement, we are creating stronger connections to local, regional and global concerns for sharks and healthy ocean ecosystems.”

Erica Blair, a graduating senior at Duke and a co-author of the new study, helped map the unique spot patterns on the sharks’ skin that were used to confirm their identities. Brian Silliman, Rachel Carson Associate Professor of Marine Conservation Biology at Duke’s Nicholas School of the Environment, also co-authored the study.

Fish warn others chemically about dangers


This june 2013 video is called Fathead minnows in my pond.

From the University of Saskatchewan in Canada:

Fish under threat release chemicals to warn others of danger

April 18, 2019

Fish warn each other about danger by releasing chemicals into the water as a signal, research by the University of Saskatchewan (USask) has found.

The USask researchers discovered that wild fish release chemicals called ‘disturbance cues’ to signal to other fish about nearby dangers, such as predators.

The findings may have implications for fish conservation efforts across the globe.

“Disturbance cues may help to explain why some fish populations crash after they decline past a certain point,” said Kevin Bairos-Novak, a graduate student member of the research team.

While researchers have been aware that fish release chemicals into the water for 30 years, this is the first time their use has been studied.

The findings, involving researchers from the USask biology department and the Western College of Veterinary Medicine, are published in the Journal of Animal Ecology.

Fish signaled most when in the presence of familiar fish, but signaled far less or not at all when in the presence of strangers, or when on their own.

The signals provoked a ‘fright response’ in fish they knew, including freezing, dashing about and then shoaling tightly together. Fish use this behavior to defend themselves against predators.

“When minnows

The research is about fathead minnows. They live in North America.

were present alongside familiar minnows, they were much more likely to produce signals that initiated close grouping of nearby fish, a strategy used to avoid being eaten by predators,” said Bairos-Novak, who is now at James Cook University, Australia.

Disturbance cues are voluntarily released by prey after being chased, startled or stressed by predators.

One of the main constituents of the signal is urea, found in fish urine.

Fathead minnows, caught at a lake, were placed in groups with familiar fish, unfamiliar fish or as isolated individuals. The research team then simulated a predator chase. The fish responded by shoaling, freezing and dashing when they received a signal from a group they knew. But they did not take significant defensive action when receiving cues from unfamiliar fish or isolated minnows.

Disturbance cues are voluntarily released by prey after being chased, startled or stressed by predators.

“It is exciting to discover a new signaling pathway in animals,” said Maud Ferrari, Bairos-Novak’s supervisor and a behavioural ecologist in the veterinary college’s Department of Veterinary Biomedical Sciences. “We found that fish are able to manipulate the behaviour of other individuals nearby by issuing a signal.”

The research was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC).