Tag: Fish

Bizarre New Species Of Fish: Ocean Sunfish


As gigantic as the ocean sunfish can be, it still seems like only half a fish.

Unique traits

Sunfish, or mola, develop their truncated, bullet-like shape because the back fin which they are born with simply never grows. Instead, it folds into itself as the enormous creature matures, creating a rounded rudder called a clavus.

Mola in Latin means “millstone” and describes the ocean sunfish’s somewhat circular shape. They are a silvery color and have a rough skin texture.

Mola are found in temperate and tropical oceans around the world. They are frequently seen basking in the sun near the surface and are often mistaken for sharks when their huge dorsal fins emerge above the water.

Their teeth are fused into a beak-like structure, and they are unable to fully close their relatively small mouths.


Size and Weight

The mola are the heaviest of all the bony fish, with large specimens reaching 14 feet vertically and 10 feet horizontally and weighing nearly 5,000 pounds. Sharks and rays can be heavier, but they’re cartilaginous fish.


Ocean sunfish can become so infested with skin parasites, they will often invite small fish or even birds to feast on the pesky critters. They will even breach the surface up to 10 feet in the air and land with a splash in an attempt to shake the parasites.


Movement and Diet

They are clumsy swimmers, waggling their large dorsal and anal fins to move and steering with their clavus. Their food of choice is jellyfish, though they will eat small fish and huge amounts of zooplankton and algae as well. They are harmless to people, but can be very curious and will often approach divers.


Threats to Survival

Their population is considered vulnerable. Sunfish frequently get snagged in drift gill nets and can suffocate on sea trash, like plastic bags, which resemble jellyfish.

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Blind Fish In Dark Caves Shed Light On The Evolution Of Sleep

Out of the approximately 3 billion letters of DNA that make up your genome, there are about a 100 letters that neither of your parents possess.

These are your own personal mutations. The machinery that copies DNA into new cells is very reliable, but it is not perfect. It makes errors at a rate equivalent to making a single typo for every 100 books filled with text.

The sperm and egg cells that fused to form you carried a few such mutations, and therefore so do you.

Changes to DNA are more likely to be disruptive than beneficial, simply because it is easier for changes to mess things up than to improve them.

This mutational burden is something that all life forms have to bear. In the long run, individuals that carry harmful mutations will, on average, produce fewer offspring than their peers.

Over many generations, this means that the mutation will dwindle in frequency. This is how natural selection is constantly ‘weeding out’ disruptive mutations from our genomes.

There is a flip side to this argument, and it is the story of the blind cave fish. If a mutation disrupts a gene that is not being used, natural selection will have no restoring effect.

This is why fish that adapt to a lifestyle of darkness in a cave tend to lose their eyes. There is no longer any advantage to having eyes, and so the deleterious mutations that creep in are no longer being weeded out.

Think of it as the ‘use it or lose it’ school of evolution.

A world without light is quite an alien place. There are many examples of fish that live in completely dark caves.

Remarkably, if you compare these fish to their relatives that live in rivers or in the ocean, you find that the cavefish often undergo a similar set of changes. Their eyes do not fully develop, rendering them essentially blind.

They lose pigmentation in their skin, and their jaws and teeth tend to develop in particular ways.

This is an example of what is known as convergent evolution, where different organisms faced with similar ecological challenges also stumble upon similar evolutionary solutions.

The changes mentioned above are all about appearance, but what about changes in behavior? In particular, when animals sleep, they generally line up with the day and night cycle.

In the absence of any daylight, how do their sleep patterns evolve?

A recent paper by Erik Duboué and colleagues addressed this question by comparing 4 groups of fish of the same species Astyanax mexicanus.

Three of the populations (the Pachón, Tinaja, and Molino) were blind cavefish that inhabited different dark caves, whereas the fourth was a surface-dwelling fish.

The authors defined sleep for their fish to be a period of a minute or more when the fish were not moving. They checked that this definition met the usual criteria.

Sleeping fish were harder to wake up, and fish that were deprived of sleep compensated by sleeping more over the next 12 hours (these are both situations that any college student is familiar with).

The researchers also tracked the speeds of all the fish, and found that, while they were awake, the cavefish moved faster or just as fast as the surface fish.

This means that it’s not that the cavefish are constantly sleep deprived and in a lethargic, sleepy state. They are just as wakeful as the surface fish (if not more so), and genuinely need less sleep.

These three cavefish populations all evolved independently, and yet they have converged on remarkably similar sleep patterns.

To study the genetics of this phenomenon, the researchers cross-bred the surface fish with the cavefish. The cave dwellers and surface fish all belong to the same species, which means that they can have viable offspring.

They found that the mixed offspring (Pachón x surface and Tinaja x surface) had a reduced need for sleep that was indistinguishable from that of their cave-dwelling parent.

Thus sleep reduction is clearly a genetic trait, and it is a dominant trait (Dominant traits are present in the offspring if they are inherited from just one parent. A recessive trait, on the other hand, will only be present if it is inherited from both parents.)

Unlocking the secrets of sleep is inherently cool science, and it also has the potential to help people suffering from sleep disorders.

Who knows, it may even lead to the superpower of doing away with sleep altogether.

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Rare Deep-Sea Creatures May Use Underwater Chimneys To Keep Their Eggs Warm

Nearly two centuries ago, among the crystalline waters and jagged volcanic outcrops of the Galapagos Islands, a young British naturalist noticed something special: Each inhabitant of these islands was so perfectly adapted to its landscape that one could tell where an animal came from just by glancing at it.

Marveling at the diversity of the area’s finches, he wrote in his diary, “one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends.”

It was the kernel of the idea that would turn Charles Darwin into one of the most famous names in biology and “On the Origin of Species” into one of the most influential texts of all time.

From a simple single-cell organism sitting in a primordial soup, life has adapted, diversified, evolved and endured.

But little did Darwin know that an even more impressive testament to life’s stunning versatility was unfolding 30 miles out to sea and 5,500 feet below the waves.

There in the utter darkness and crushing pressures of the deep ocean, a rare stingray-like creature called a Pacific white skate today lays its eggs among the hot plumes that gush from hydrothermal vents.

This seems daring — the underwater equivalent of a bird building its nest at the mouth of a volcano — but it may be a stunningly sophisticated maneuver, scientists say.

Eggs incubate faster when they’re warm, increasing the likelihood that the offspring will survive to perpetuate their parents’ DNA.

I think it’s phenomenal,” said Dave Ebert, program director of the Pacific Shark Research Center at Moss Landing Marine Labs in California and co-author of a new study about the discovery.

As far as he is aware, it is the first time any marine animal has been seen exploiting the hydrothermal vent environment for this purpose.

This is a very complex behavior pattern,” Ebert said, “and it gets into why there are so many different species” of skate.

Skates, sometimes called “flat sharks,” are a diverse family within the class of fish called Elasmobranchs, which also includes sharks and rays. Like their cousins, skates are ancient, boneless and predatory.

Their kite-shaped bodies have been seen soaring over the bottoms of every ocean in the world.

The Pacific white skate is the deepest-dwelling species in this group. Ranging between half a mile to nearly two miles below the surface, they are an enigma to scientists — beyond the reach of all but the sturdiest submersibles.

Almost nothing is known about them,” said Pelayo Salinas de Léon, a marine biologist at the Charles Darwin Foundation. Only half a dozen specimen have ever been studied in a lab.

On a warm June morning, the researchers dropped their remote-operated underwater vehicle, or ROV, into the azure waters of the Pacific.

For 90 minutes it sank deeper and deeper, the ocean around it darkening to cobalt, then navy, then black. A long fiber-optic cable tethered the craft to the ship where scientists watched a live feed of the descent.

No sooner had the ROV reached the sea floor than they spotted a cluster of rectangular pouches clustered near the base of one of the black-smoker chimneys.

It was instant jackpot,” Salinas recalled.

The egg cases were about the size of iPhones and the color of banana peels, with tails at the corners that give them their common name — “mermaid’s purse.”

More than half were spotted within 65 feet of a chimney, and nearly 90 percent were in places where the water temperature was higher than its average of 37 degrees Fahrenheit.

The researchers’ report of their discovery was published Thursday in the journal Scientific Reports.

They continue to work on their analysis of the biodiversity survey at Iguanas-Pinguinos, with Salinas estimating that they identified about 30 new species.

There probably are hundreds, if not thousands more, to be found. The ocean floor is the largest habitat on Earth, but the surfaces of the moon and Mars are better known.

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World’s Heaviest Bony Fish Identified And Correctly Named

Last December 6 in Tokyo, the world’s heaviest bony fish ever caught – weighing a whopping 2,300 kilogrammes – has been identified and correctly named by Japanese experts.

The fish is a Mola alexandrini bump-head sunfish, and not a member of the more commonly known Mola mola ocean sunfish species as originally thought, according to researchers from Hiroshima University.

Bony fish have skeletons made of bone rather than cartilage, as is the case for sharks or rays.

In the study, published in the journal Ichthyological Research, researchers led by Etsuro Sawai referred to more than one thousand documents and specimens from around the world – some of which date back 500 years.

Their aim was to clarify the scientific names for the species of the genus Mola in fish.

They also solved a case of mistaken identity. The Guinness World Records lists the world’s heaviest bony fish as Mola mola, researchers said.

However, Sawai’s team found a female Mola alexandrini specimen of 2,300 kilogramme and 2.72 meter caught off the Japanese coast in 1996 as the heaviest bony fish ever recorded.

Sawai’s team re-identified it as actually being a Mola alexandrini based on its characteristic head bump, chin bump and rounded clavus although this specimen was identified Mola mola until now.

Ocean sunfishes count among the world’s largest bony fish, and have for centuries attracted interest from seafarers because of their impressive size and shape, researchers said.

Specimens can measure up to three meters (total length), and many weighing more than two thousand kilogrammes have been caught.

Instead of a caudal fin, sunfish have a broad rudder-like lobe called a clavus, they said.

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Are Sharks Endangered Because Of Shark Fin Soup?

Many people fear sharks, when the reality is they have far more reason to fear us!

As one writer put it perfectly: , “sharks are winding up on our dinner table more often than we do on theirs”.

To such an extent that we humans are basically decimating sharks.

The shark-fin market is a huge threat to the world’s shark populations. It has become a multibillion-dollar industry since the early 1980s.

Demand exploded with the rapid growth of China’s economy. Before then sharks weren’t really targeted by fisheries, but over those 30 years, many species have become threatened.

True catch numbers are a mystery because much of the trade happens on the black market.

On top of the conservation impacts, the methods for taking fins are cruel.

Shark-finning” is the practice of chopping off a shark’s fins, and dumping the often-live animal back into the sea. No longer able to swim, the injured shark then drowns, bleeds to death, or is an easy target for predators.

What drives this is the high price of shark fins on the international market. They have become one of the world’s most precious products.

Shark meat itself isn’t very valuable, so it is usually thrown overboard. Other parts that are used include skin, liver oil, cartilage, corneas, and blood.

Often shark parts are put into medicines and supplements.

The fins fetch the highest price. A pound of shark fin can cost $300. And depending on which numbers you believe, people will pay from a hundred dollars up to $2,000 for a bowl of shark fin soup. For soup!

The shark fin industry’s center is Hong Kong, but shark catches come from worldwide. Countries that take the most sharks include Indonesia, India, Mexico, Spain, and Taiwan.

A team of researchers recently got past the mystery of numbers involved in the shark fin trade. They made the first estimate of shark catches that was independent of world fisheries data (Clarke et al. 2006).

To do so they combined official catch data with weights of fins from fin auctions in Hong Kong, for more accurate estimates.

They concluded that the amount of shark biomass (weight) involved in the fin trade is three to four times higher than what is reported.

Estimates of the total number of sharks traded for fins worldwide ranged from 26 to 73 million per year. Clearly, sharks are being over-exploited.

Marine ecosystems have complex food webs. Sharks are top predators; altering their numbers has a big impact on other species that “cascades” through the entire system.

As shark numbers decline, their prey species have increased (e.g. rays), who in turn are taking more of their own prey (e.g. scallops). As a result, many species of mollusks are rapidly declining.

Researchers are also seeing the ripple effects of dramatic shark declines in the Caribbean. Fish usually eaten by sharks are now increasing in number, such as groupers.

Those predators feed on parrotfish, which in turn eat algae off coral reefs. The result? Too many groupers = too few parrotfish = too much algae.

This is altering marine systems by limiting the resources available to all species that depend on coral reef habitats.

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Watch These Leaping Electric Eels Validate One Of Science History’s Wackiest Stories

Kenneth Catania, a biologist at Vanderbilt University, takes a breath. He hasn’t known this tale long, but it’s quickly become one of his favorites.

Alexander von Humboldt, a famous German scientist, was on an expedition to document the geography and ecology of South America.

He traveled for the better part of five years, debunking myths about mystical lakes, observing celestial events, naming new creatures, and investigating questions large and small.

He once spent three whole months studying bird feces.

And one part of his quest was to get eels to do experiments on electricity,” Catania said, “since people were very excited about electricity at the time, but they didn’t understand the nature of it.

Eventually, Humboldt arrived at a village by a muddy stream in the Amazon rainforest, where locals said they could catch him an electric eel.

They told him, ‘We’ll fish with horses,‘ ” Catania recounted. Illustrations from the time show fishermen herding dozens of horses into a shallow pool while eels leap at the big mammals’ throats, delivering a massive shock with each strike.

The spectacle allegedly sapped the eels of their electricity, allowing Humboldt to wade in and catch one to take home.

The story was celebrated when it was first told in 1807, but later scientists were more skeptical. One biologist wrote in the Atlantic Monthly that he considered the story “tommyrot.”

Catania himself gently suggested that it was a “tale.” For one thing, this behavior had never been documented in eels. For another, Humboldt’s original account of the incident doesn’t even mention the creatures leaping.

Within 200 years of Humboldt writing it down, the entire anecdote was deemed a flight of 19th-century fancy.

Until Catania accidentally re-created the incident in his lab.

There’s a lot of good puns here,” he joked. “But it was really shocking.

Catania’s study, published Monday in the Proceedings of the National Academy of Sciences, shows that Humboldt’s account wasn’t so fanciful after all.

But he didn’t set out to prove Humboldt right. Catania specializes in animals with weird behaviors: worms that emerge from the ground in response to “grunts,” moles that smell in stereo.

And, of course, eels.

As the net approached, the bigger eels would suddenly reverse course so they were swimming toward it. Then they’d launch out of the water and strike the handle of their net with their chins.

The behavior was odd, to be sure, but Catania didn’t think much of it. He added it to his notes, marking it as something to look into later.

Then he noticed the data from the recorder he used to document the eel’s electrical pulses. At exactly the same time they were leaping, the eels emitted a volley of incredibly high-voltage pulses.

It didn’t take much research to discover Humboldt’s account of the same behavior more than 200 years ago.

A book on the fish of northeastern South America, written by Humboldt’s friend and protege Robert Schomburgk, bore an illustration of the gruesome encounter that looked exactly like what Catania had encountered with his net.

So Catania set up another experiment, this time using a toy crocodile head bedazzled with light-emitting diodes to simulate an “attacker.”

This behavior is exactly what you’d expect the eels to have done from Humboldt’s story,” he said.

The eels positioned themselves as high as possible along the crocodile’s head, sending increasingly powerful pulses of electricity into a conductive strip affixed to its front.

These results explain why an eel would risk jumping out of the water to stun his attacker: It’s taking advantage of a very basic principle of electronics.

The way Catania describes it, an eel is like a battery, with a positive pole at its front and a negative one on its tail.

Electricity always wants to flow from the positive to the negative pole, an easy task when the eel is totally submerged and the current can be conducted by the water.

But when the eel leaps up to shock a horse — or a crocodile head — the electricity must travel through the body of the attacker in order to reach the negative pole. This means that the shock administered to the attacker is much more intense.

It’s a pretty sophisticated behavior especially when you consider how long it took us humans to figure out how electrical circuits work.

And it can be useful to eels during the Amazon’s dry season, when streams turn to mud patches, cutting off routes of escape.

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Could Aquaculture Solve Africa’s Fishing Crisis?

Marine fisheries in Africa are over-exploited, but with the right type of fish and support from NGOs, smallholders could help bring about growth.

Fish is a critical source of dietary protein in sub-Saharan Africa, providing an estimated 22% of protein intake.

But with marine fisheries over-exploited, African fish production is failing to keep up with rising populations.

How should that gap be filled to protect this vital source of nutrition?

Aquaculture can do it, according to experts from the UN’s Food and Agriculture Organisation and the WorldFish research organization.

But it will only work if there’s a shift away from decades-old approaches to aquaculture development, which uses farm ponds.

For real impact on overall fish production and access, they say, there needs to be a greater emphasis on smallholders joining forces and helping to develop a commercial fish farming sector.

Per capita fish supplies in Africa are dwindling,” says Malcolm Beveridge, director for aquaculture and genetic at WorldFish, one of the CGIAR research centres.

In Malawi, they fell from 10kg to 6kg per person between 1986 and 2006. Aquaculture has the potential to increase supplies of this affordable nutritious food for poor and vulnerable consumers.

Historically, aquaculture development in Africa has targeted the poorest people to address hunger through small on-farm ponds.

This has proven valuable for household food and nutrition security and will continue to have a place.

But on-farm aquaculture isn’t meeting the overall supply gap now, and isn’t likely to do so in future for a rapidly growing and increasingly urbanised population.

Small ponds reliant on meagre household scraps and on-farm waste will produce only a few kilograms of fish per year,” says Beveridge.

This is often important for the family and worth supporting as part of building livelihood diversification strategies. But the benefits rarely extend beyond the household and immediate neighbours.

This partly explains why, to date, African aquaculture has remained insignificant in global terms. Total production was 1,288,320 tonnes in 2010, representing just 2.2% of global production.

Discount Egypt (Africa’s major producer) and the figure for sub-Saharan Africa on its own was just 359,790 tonnes for 2010 – a mere 0.6% of world production.

But things are already changing. It may be starting from a low base, but aquaculture in sub-Saharan Africa is growing: in 2000, production was just 55,690 tonnes, so it saw almost seven-fold growth between then and 2010.

Much of this growth is taking place in countries including Ghana, Nigeria, Uganda, Kenya, and Namibia, thanks partly to initiatives such as the FAO’s Special Programme for Aquaculture in Africa and the Nepad action plan for the development of African fisheries and aquaculture, which are providing policy and technical support to a groundswell of aquaculture enterprises.

Spada, established in 2007, stated an aim of increasing aquaculture in Africa by 200% over the next decade. But the extent to which that will impact upon food security depends on how it is achieved.

In theory, more fish should mean lower prices and greater access, but that isn’t guaranteed if production is concentrated amongst a small number of large-scale producers near urban centres, or if the fish is exported.

It’s therefore essential that smallholders help drive the growth, according to Rohana Subasinghe, senior aquaculture officer at the FAO.

This will help ensure that the most food insecure benefit from increased production. But smallholders can’t do it individually, because entry costs can be prohibitive for small-scale producers, who tend to be risk-averse.

Smallholders are extremely important in Africa, but you have to operate on a certain scale in aquaculture,” says Subasinghe.

So smallholders will need to work together in clusters, so they can be more empowered and operate as a group with better market access.

“These SMEs – made up of smallholders – will help keep the ultimate objective of agriculture in mind, which is alleviating poverty and improving food security.

Another factor to get right is the type of fish produced. The vast majority of farmed fish in Africa is freshwater, mainly the Nile tilapia and sharptooth catfish.

These omnivorous fish are relatively easy to raise, and there is strong demand for them. New strains of the Nile tilapia released this year Egypt, Ghana and Malawi are also up to 30% faster-growing than traditional strains, and have been heralded as a leap forward for African aquaculture.

But bigger is not always better, in food security terms.

For development actors, then, the challenge is to provide the right kind of support to aquaculture in different places.

On the one hand, on-farm ponds will remain important and can be developed further to improve household food security.

For the very poorest, this is crucial. Work in Malawi, for example, has shown how successful Integrated Agriculture-Aquaculture can be at the farm level, providing not just the protein from fish but raising overall agricultural productivity.

On the other hand, NGOs can also play a vital role in developing and fostering networks of aquaculture SMEs formed of smallholders, and helping the sector develop in such a way that it contributes to wider food and nutrition security.

Governments have already demonstrated political will, says Subasinghe. Kenya has made aquaculture a core priority in its fisheries department. But it is NGOs who can really help make things happen.

Much of Africa already has the right conditions in terms of soils, water, temperatures and market demand to farm fish successfully.

What’s important now is to shape growth in such a way that it has real impacts on hunger and undernutrition.

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Fossil Holds New Insights Into How Fish Evolved Onto Land

The fossil of an early snake-like animal – called Lethiscus stocki – has kept its evolutionary secrets for the last 340-million years.

Now, an international team of researchers, led by the University of Calgary, has revealed new insights into the ancient Scottish fossil that dramatically challenge our understanding of the early evolution of tetrapods, or four-limbed animals with backbones.

Their findings have just been published in the research journal Nature.

It forces a radical rethink of what evolution was capable of among the first tetrapods,” said project lead Jason Anderson, a paleontologist and Professor at the University of Calgary Faculty of Veterinary Medicine (UCVM).

Before this study, ancient tetrapods – the ancestors of humans and other modern-day vertebrates – were thought to have evolved very slowly from fish to animals with limbs.

We used to think that the fin-to-limb transition was a slow evolution to becoming gradually less fish like,” he said.

But Lethiscus shows immediate, and dramatic, evolutionary experimentation. The lineage shrunk in size, and lost limbs almost immediately after they first evolved. It’s like a snake on the outside but a fish on the inside.

Using micro-computer tomography (CT) scanners and advanced computing software, Anderson and study lead author Jason Pardo, a doctoral student supervised by Anderson, got a close look at the internal anatomy of the fossilized Lethiscus.

After reconstructing CT scans its entire skull was revealed, with extraordinary results.

The anatomy didn’t fit with our expectations,” explains Pardo.

Many body structures didn’t make sense in the context of amphibian or reptile anatomy.” But the anatomy did make sense when it was compared to early fish.

We could see the entirety of the skull. We could see where the brain was, the inner ear cavities. It was all extremely fish-like,” explains Pardo, outlining anatomy that’s common in fish but unknown in tetrapods except in the very first.

The anatomy of the paddlefish, a modern fish with many primitive features, became a model for certain aspects of Lethiscus’ anatomy.

When they included this new anatomical information into an analysis of its relationship to other animals, Lethiscus moved its position on the ‘family tree’, dropping into the earliest stages of the fin-to-limb transition.

It’s a very satisfying result, having them among other animals that lived at the same time,” says Anderson.

The results match better with the sequence of evolution implied by the geologic record.

Lethiscus also has broad impacts on evolutionary biology and people doing molecular clock reproductions of modern animals,” says Anderson.

They use fossils to calibrate the molecular clock. By removing Lethiscus from the immediate ancestry of modern tetrapods, it changes the calibration date used in those analyses.

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Climate Change May Shrink the Fishes In The World

Warming temperatures and loss of oxygen in the sea will shrink hundreds of fish species—from tunas and groupers to salmon, thresher sharks, haddock and cod—even more than previously thought, a new study concludes.

Because warmer seas speed up their metabolisms, fish, squid and other water-breathing creatures will need to draw more oxyen from the ocean. At the same time, warming seas are already reducing the availability of oxygen in many parts of the sea.

A pair of University of British Columbia scientists argue that since the bodies of fish grow faster than their gills, these animals eventually will reach a point where they can’t get enough oxygen to sustain normal growth.

What we found was that the body size of fish decreases by 20 to 30 perent for every 1 degree Celsius increase in water temperature,” says author William Cheung, director of science for the university’s Nippon Foundation—Nereus Program.

These changes, the scientists say, will have a profound impact on many marine food webs, upending predator-prey relationships in ways that are hard to predict.

“Lab experiments have shown that it’s always the large species that will become stressed first,” says lead author Daniel Pauly, a professor at the university’s Institute for the Ocean and Fisheries, and principal investigator for the Sea Around Us.

Small species have an advantage, respiration-wise.

Still, while many scientists applaud the discovery, not all agree that Pauly’s and Cheung’s work supports their dramatic findings. The study was published today in the journal Global Change Biology.

Pauly is perhaps best known for his global, sometimes controversial, studies of overfishing.

But since his dissertation in the 1970s, he has researched and promoted a principle that suggests fish size is limited by the growth capacity of gills.

Based on this theory, he, Cheung and other authors published research in 2013 that showed average body weight for some 600 species of ocean fish could shrink 14-24 percent by 2050 under climate change.

It’s a difficult concept for people to imagine because we breathe air,” Pauly says. “Our problem is getting enough food—not oxygen. But for fish, it’s very different. For humans, it would be like trying to breathe through a straw.

Other scientists have linked oxygen to smaller fish sizes. In the North Sea, for example, haddock, whiting, herring and sole have already seen significant loss in size in areas of the sea with less oxygen.

Still, Pauly’s and Cheung’s 2013 results were criticized in some corners as overly simplistic. Earlier this year, a group of European physiologists argued that Pauly’s basic premise about gill size was, itself, flawed.

So Pauly and Cheung used more sophisticated models and re-examined their theory.

The new paper doubles down on their earlier case, explains the gill theory in more detail and argues that it can and should be used as a guiding principle.

The new work goes on to suggests their original conclusions actually underestimated the scale of the problem fish will soon face.

The earlier paper, for example, suggested the size of some species, such as tuna, may be less affected by climate change.

But the new research states that fast-swimming ever-mobile tunas, which already consume significant oxygen, may be more susceptible than some other fish.

In fact, in parts of the tropical Atlantic, Cheung says, there is a vast region where oxygen is already low in the open ocean. Other studies have shown tunas altering their range to avoid that bad water.

Tunas’ distributions have followed very closely the bounds of these oxygen minimum zones,” Cheung says.

Some fish experts find Pauly’s and Cheung’s gill theory and new work convincing.

Jeppe Kolding, a biology professor at the University of Bergen in Norway, who studies fish in Africa, says Pauly’s gill concept is the only thing he’s found that elucidates the dwarfing he’s seen in Nile tilapia, guppies, and a type of sardine found in Zambia and in Lake Victoria.

It does explain the phenomena I have encountered in Africa,” he says.

Nick Dulvy, a marine biologist at Simon Fraser University, says his own research “tends to confirm” Pauly’s ideas.

It is absoutely an inevitability that as fish grow heavier they will eventually reach a point where oxygen intake does not match their metabolic demand.

Still, one of Pauly’s earlier critics, Sjannie Lefevre, a physiologist with the University of Oslo in Norway, lead author of the critique published earlier this year in the same journal, continues to find Pauly’s gill theory wanting.

I am not at all impressed or convinced by their attempt to refute our arguments,” Lefevre says, adding that she doesn’t “consider the new results any more reliable.”

She says fish absolutely are capable of growing larger gills. “There are no geometric constraints stopping gills from growing as fast as the body of a fish,” she says.

She and Poertner could not view the work more differently. Lefevre says she hopes ecologists and modelers keep “an open and cautious mind” before accepting such unifying theories.

Poertner, on the other hand, maintains that Pauly’s and Cheung’s work is a great example of the right way to apply such theories.

The new research shows how “careful use of an overarching principle in a wide set of observations across species can support insight that is difficult to reach otherwise,” he says.

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Goldfish Make Alcohol In Their Cells To Survive Months Without Oxygen In Icy Waters

Goldfish can survive for months at a time in oxygen-free water. They convert lactic acid into ethanol which keeps them alive under frozen lakes.

A little bit of alcohol probably means they lose their inhibitions too. Goldfish and carp produce at least 50 mg per millilitre in their blood.

This puts them above the legal drink drive limit in most countries“, lead researcher Michael Berenbrink said.

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