Tasmania’s salmon industry detonates underwater bombs to scare away seals – but at what cost?


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Benjamin J. Richardson, University of TasmaniaAustralians consume a lot of salmon – much of it farmed in Tasmania. But as Richard Flanagan’s new book Toxic shows, concern about the industry’s environmental damage is growing.

With the industry set to double in size by 2030, one dubious industry practice should be intensely scrutinised – the use of so-called “cracker bombs” or seal bombs.

The A$1 billion industry uses the technique to deter seals and protect fish farming operations. Cracker bombs are underwater explosive devices that emit sharp, extremely loud noise impulses. Combined, Tasmania’s three major salmon farm operators have detonated at least 77,000 crackers since 2018.

The industry says the deterrent is necessary, but international research shows the devices pose a significant threat to some marine life. Unless the salmon industry is more strictly controlled, native species will likely be killed or injured as the industry expands.

pile of grey and white fish
Tasmanian salmon farming is a billion-dollar industry.
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Protecting a lucrative industry

Marine farming has been growing rapidly in Tasmania since the 1990s, and Atlantic salmon is Tasmania’s most lucrative fishery‑related industry. The salmon industry comprises three major producers: Huon Aquaculture, Tassal and Petuna.

These companies go to great effort to protect their operations from fur seals, which are protected in Australia with an exemption for the salmon industry.

Seals may attack fish pens in search of food and injure salmon farm divers, though known incidents of harm to divers are extremely rare.

The industry uses a number of seal deterrent devices, the use of which is approved by the government. They include:

  • lead-filled projectiles known as “beanbags”, which are fired from a gun
  • sedation darts fired from a gun
  • explosive charges or “crackers” thrown into the water which detonate under the surface.

In June this year, the ABC reported on government documents showing the three major salmon producers had detonated more than 77,000 crackers since 2018. The documents showed how various seal deterrent methods had led to maiming, death and seal injuries resulting in euthanasia. Blunt-force trauma was a factor in half the reported seal deaths.

A response to this article by the salmon industry can be found below. The industry has previoulsy defended the use of cracker bombs, saying it has a responsibility to protect workers. It says the increased use of seal-proof infrastructure means the use of seal deterrents is declining. If this is true, it’s not yet strongly reflected in the data.




Read more:
Here’s the seafood Australians eat (and what we should be eating)


salmon farm infrastructure in water
Seal deterrents are deployed to protect salmon farm operations.
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Piercing the ocean silence

Given the prevalence of seal bomb use by the salmon industry, it’s worth reviewing the evidence on how they affect seals and other marine life.

A study on the use of the devices in California showed they can cause horrific injuries to seals. The damage includes trauma to bones, soft tissue burns and prolapsed eye balls, as well as death.

And research suggests damage to marine life extends far beyond seals. For example, the devices can disturb porpoises which rely on echolocation to find food, avoid predators and navigate the ocean. Porpoises emit clicks and squeaks – sound which travels through the water and bounces off objects. In 2018, a study found seal bombs could disturb harbour porpoises in California at least 64 kilometres from the detonation site.

There is also a body of research showing how similar types of industrial noise affect marine life. A study in South Africa in 2017 showed how during seismic surveys in search of oil or gas, which produce intense ocean noise, penguins raising chicks often avoided their preferred foraging areas. Whales and fish have also shown similar avoidance behaviour.

The study showed underwater blasts can also kill and injure seabirds such as penguins. And there may be implications from leaving penguin nests unattended and vulnerable to predators, and leaving chicks hungry longer.

Research also shows underwater explosions damage to fish. One study on caged fish reported profound trauma to their ears, including blistering, holes and other damage. Another study cited official reports of dead fish in the vicinity of seal bomb explosions.




Read more:
Climate change is causing tuna to migrate, which could spell catastrophe for the small islands that depend on them


dolphin jumps out of waves
Man-made noise can disturb a variety of marine animals, including porpoises.
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Shining a light

Clearly, more scientific research is needed into how seal bombs affect marine life in the oceans off Tasmania. And regulators should impose far stricter limits on the salmon industry’s use of seal bombs – a call echoed by Tasmania’s Salmon Reform Alliance.

All this is unfolding as federal environment laws fail to protect Australian plant and animal species, including marine wildlife.

And the laws in Tasmania are far from perfect. In 2017, Tasmania’s Finfish Farming Environmental Regulation Act introduced opportunities for better oversight of commercial fisheries. However, as the Environmental Defenders Office (EDO) has noted, the director of Tasmania’s Environment Protection Authority can decide on license applications by salmon farms without the development necessarily undergoing a full environmental assessment.

Tasmania’s Marine Farming Planning Act covers salmon farm locations and leases. As the EDO has noted, the public is not notified of some key decisions under the law and has very limited public rights of appeal.

Two relevant public inquiries are underway – a federal inquiry into aquaculture expansion and a Tasmanian parliamentary probe into fin-fish sustainability. Both have heard evidence from community stakeholders, such as the Tasmanian Alliance for Marine Protection and the Tasmanian Conservation Trust, that the Tasmanian salmon industry lacks transparency and provides insufficient opportunities for public input into environmental governance.

The Tasmanian government has thrown its support behind rapid expansion of the salmon industry. But it’s essential that the industry is more tightly regulated, and far more accountable for any environmental damage it creates.




Read more:
Why Indigenous knowledge should be an essential part of how we govern the world’s oceans



In a statement in response to this article, the Tasmanian Salmonid Growers Association, which represents the three producers named above, said:

Around $500 million has been spent on innovative pens by the industry. These pens are designed to minimise risks to wildlife as well as to fish stocks and the employees. We believe that farms should be designed to minimise the threat of seals, but we also understand that non-lethal deterrents are a part of the measures approved by the government for the individual member companies to use. If these deterrents are used it is under strict guidelines, sparingly, and in emergency situations when staff are threatened by these animals, which can be very aggressive.

Tasmania has a strong, highly regulated, longstanding salmon industry of which we should all be proud. The salmon industry will continue its track record of operating at world’s best practice now and into future. Our local people have been working in regional communities for more than 30 years, to bring healthy, nutritious salmon to Australian dinner plates, through innovation and determination.The Conversation

Benjamin J. Richardson, Professor of Environmental Law, University of Tasmania

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Pregnant male seahorses support up to 1,000 growing babies by forming a placenta


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Jessica Suzanne Dudley, Macquarie University and Camilla Whittington, University of SydneySupplying oxygen to their growing offspring and removing carbon dioxide is a major challenge for every pregnant animal. Humans deal with this problem by developing a placenta, but in seahorses — where the male, not the female, gestates and gives birth to the young — exactly how it worked hasn’t always been so clear.

Male seahorses incubate their embryos inside a pouch, and until now it was unclear how the embryos “breathe” inside this closed structure. Our new study, published in the journal Placenta, examines how pregnant male seahorses (Hippocampus abdominalis) provide oxygen supply and carbon dioxide removal to their embryos.

We examined male seahorse pouches under the microscope at different stages of pregnancy, and found they develop complex placental structures over time — in similar ways to human pregnancy.

Male pot-bellied seahorses have large fleshy pouches where embryos develop during pregnancy.
by Aaron Gustafson



Read more:
Curious Kids: Is it true that male seahorses give birth?


A pregnant dad gestating up to 1,000 babies

Male pregnancy is rare, only occurring in a group of fish that includes seahorses, seadragons, pipehorses and pipefishes.

Pot-bellied seahorse males have a specialised enclosed structure on their tail. This organ is called the brood pouch, in which the embryos develop.

The female deposits eggs into the male’s pouch after a mating dance and pregnancy lasts about 30 days.

While inside the pouch, the male supplies nutrients to his developing embryos, before giving birth to up to 1,000 babies.

Male pot-bellied seahorse filling his pouch with water in a mating display.
by Kymberlie R. McGuire

Embryonic development requires oxygen, and the oxygen demand increases as the embryo grows. So too does the need to get rid of the resulting carbon dioxide efficiently. This presents a problem for the pregnant male seahorse.

Enter the placenta

In egg-laying animals — such as birds, monotremes, certain reptiles and fishes — the growing embryo accesses oxygen and gets rid of carbon dioxide through pores in the egg shell.

For animals that give birth to live young, a different solution is required. Pregnant humans develop a placenta, a complex organ connecting the mother to her developing baby, which allows an efficient exchange of oxygen and carbon dioxide (it also gets nutrients to the baby, and removes waste, via the bloodstream).

Placentae are filled with many small blood vessels and often there is a thinning of the tissue layers that separate the parent’s and baby’s blood circulations. This improves the efficiency of oxygen and nutrient delivery to the fetus.

Surprisingly, the placenta is not unique to mammals.

Some sharks, like the Australian sharpnose shark (Rhizoprionodon taylori) develop a placenta with an umbilical cord joining the mother to her babies during pregnancy. Many live-bearing lizards form a placenta (including very complex ones) to provide respiratory gases and some nutrients to their developing embryos.

Our previous research identified genes that allow the seahorse father to provide for the developing embryos while inside his pouch.

Our new study shows that during pregnancy the pouch undergoes many changes similar to those seen in mammalian pregnancy. We focused on examining the brood pouch of male seahorses during pregnancy to determine exactly how they provide oxygen to their developing embryos.

A Pot-belly seahorse (Hippocampus abdominalis) floats in water
By viewing the seahorse pouch under the microscope at various stages of pregnancy, we found that small blood vessels grow within the pouch.
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What we found

By viewing the seahorse pouch under the microscope at various stages of pregnancy, we found that small blood vessels grow within the pouch, particularly towards the end of pregnancy. This is when the baby seahorses (called fry) require the most oxygen.

The distance between the father’s blood supply and the embryos also decreases dramatically as the pregnancy goes on. These changes improve the efficiency of transport between the father and the embryos.

Interestingly, many of the changes that occur in the seahorse pouch during pregnancy are similar to those that occur in the uterus during mammalian pregnancy.

We have only scratched the surface of understanding the function of the seahorse placenta during pregnancy.

There is still much to learn about how these fathers protect and nourish their babies during pregnancy — but our work shows the morphological changes to seahorse brood pouches have a lot in common with the development of mammalian placentae.




Read more:
The secret sex life and pregnancy of a seahorse dad


The Conversation


Jessica Suzanne Dudley, Postdoctoral Fellow, Macquarie University and Camilla Whittington, Senior lecturer, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Photos from the field: why losing these tiny, loyal fish to climate change spells disaster for coral


Catheline Froehlich, Author provided

Catheline Y.M. Froehlich, University of Wollongong; Marian Wong, University of Wollongong, and O. Selma Klanten, University of Technology SydneyEnvironmental scientists see flora, fauna and phenomena the rest of us rarely do. In this series, we’ve invited them to share their unique photos from the field.


If you’ve ever dived on a coral reef, you may have peeked into a staghorn coral and seen small fish whizzing through its branches. But few realise that these small fish, such as tiny goby fish, play a crucial role in helping corals weather the storm of climate change.

But alarmingly, our new research found gobies decline far more than corals do after multiple cyclones and heatwaves. This is concerning because such small fish — less than 5 centimetres in length — are critical to coral and reef health.

Unfortunately, the number of cyclones and heatwaves is on the rise. These disasters have begun to occur back-to-back, leaving no time for marine life to recover.

With the recent push by UNESCO to list the Great Barrier Reef as “in danger”, the world is currently on edge about the status of coral reefs. We’re at a critical stage to take all the necessary measures to save coral reefs worldwide, and we must broaden our focus to understand how the important relationships between corals and fish are affected.

This five-lined coral goby (Gobiodon quinquestrigatus) is taking a break on a coral branch.
Catheline Froehlich, Author provided

Goby fish: the snack-sized friends of coral

In all environments, organisms can form relationships where they work together to improve each other’s health. This is called a mutual symbiosis, like a you-scratch-my-back principle.

In coral reefs, other examples of mutual symbioses include invisible zooxanthellae algae living within coral tissue, small cleaner fish removing parasites from big fish, and eels and groupers hunting together.

While this shark is taking a nap, small yellow fish are hiding under its fin, and it is also getting cleaned by a cleaner wrasse (slender black fish with neon blue outline).
Catheline Froehlich, Author provided
Living on the edge: some fish live inside branched corals, while others live around the perimeter of coral bommies like this.
Catheline Froehlich, Author provided

Gobies that live in corals are small, snack-sized fish that rarely venture beyond the prickly borders of their protective coral homes. The Great Barrier Reef is home to more than 20 species of coral gobies, which live in more than 30 species of staghorn corals.

In return for the coral’s protection, the gobies pluck off harmful algae growing on coral branches, produce a toxin to deter potential coral-eating fish, and reduce heat stress by swimming around the coral and stopping stagnant water build up.

The blue-spotted coral goby (Gobiodon erythrospilus) is holding its position by pushing its front pectoral fins against coral branches.
Catheline Froehlich, Author provided
Paired romance: these lemon coral gobies (Gobiodon citrinus) live in monogamous pairs while also sharing their coral with a humbug damselfish (Dascyllus aruanus).
Catheline Froehlich, Author provided

Even if their corals become stressed and bleached, they remain steadfast within the coral, helping it to survive. Without their full-time cleaning staff, corals would be more susceptible when threatened with climate change.

Unfortunately, just like Nemos (clownfish) living inside anemones, climate change threatens the mutual symbioses between gobies and corals.

Coral gobies in decline

While SCUBA diving, we surveyed corals and their goby friends over a four-year period (2014-17) of near-continuous devastation at Lizard Island, on the Great Barrier Reef. Over this time, two category 4 cyclones and two prolonged heatwaves wreaked havoc on this world-renowned reef.

Coral gobies are often hard to spot, so we use underwater flashlights to identify them correctly.
Catheline Froehlich, Author provided

What we saw was alarming. After the two cyclones, the 13 goby species (genus Gobiodon) and 28 coral species (genus Acropora) we surveyed declined substantially.

But after the two heatwaves, gobies suddenly fared even worse than corals. While some coral species persisted better than others, 78% no longer housed gobies.

Importantly, every single goby species either declined, or worse, completely disappeared. The few gobies we found were living alone, which is especially concerning because gobies breed in monogamous pairs, much like most humans do.

After cyclones and heatwaves, we found a lot of dead corals surrounding pockets of living corals and reef life at Lizard Island.
Catheline Froehlich, Author provided
We surveyed coral and goby survival and often found a lot of coral debris after heatwaves.
Catheline Froehlich, Author provided

Without urgent action, the outlook is bleak

More and more studies are showing reef fish behave differently in warmer and more acidic water.

Warmer water is even changing reef fish on a genetic level. Fish are struggling to reproduce, to recognise what is essential habitat, and to detect predators. Research has shown clownfish, for example, could not tell predatory fish (rockcods and dottybacks) from non-predators (surgeonfishes and rabbitfishes) when exposed to more acidic seawater.

Finding Nemo swimming in anemone in Lizard Island. The bright pink surrounding it is the column of the anemone. Picture the column as your neck and the tentacles as your hair.
Abigail Shaughnessy, Author provided

The bigger picture looks bleak. Corals are likely to become increasingly vulnerable if their symbiotic gobies and other inhabitants continue to decline. This could lead to further disruptions in the reef ecosystem because mutual symbioses are important for ecosystem stability.

We need to broaden our focus to understand how animal interactions like these are being affected in these trying times. This is an emerging field of study that needs more research in the face of climate change.

Here, one of my assistants, Al Alder, is measuring the coral so that we can tell what happens to the size of corals after each climatic disaster.
Catheline Froehlich, Author provided
Several fish that are not coral gobies are still found swimming about even after four years of climatic disasters at Lizard Island.
Catheline Froehlich, Author provided

On a global scale, multiple disturbances from cyclones and heatwaves are becoming the norm. We need to tackle the problem from multiple angles. For example, we must meet net zero carbon emissions by 2050 and stop soil erosion and agricultural runoff from flowing into the sea.

If we do not act now, gobies and their coral hosts may become a distant memory in this warming climate.The Conversation

Catheline Y.M. Froehlich, PhD Fellow, University of Wollongong; Marian Wong, Senior Lecturer, University of Wollongong, and O. Selma Klanten, Research Scientist, University of Technology Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Giant sea bass are thriving in Mexican waters – scientific research that found them to be critically endangered stopped at the US-Mexico border


Giant sea bass are listed as a critically endangered species.
Maru Brito, CC BY-ND

Arturo Ramírez-Valdez, University of California San DiegoI was looking at the seafloor, focused on identifying fish species as I normally did when diving off of the California coast, when suddenly I felt something large above me. When I turned my head I saw a giant fish – more than 6 feet (2 meters) long – calmly interested in the air bubbles coming from my SCUBA regulator. This was 2016 and was my first encounter with a giant sea bass.

I am a marine ecologist, and I study how international borders pose challenges for conservation and management efforts in the marine environment. Although there are no walls or fences in the ocean, borders still act as stark barriers for a variety of things.

Giant sea bass live off the west coast of North America in both Mexican and U.S. waters. I have found that large differences in regulation and research effort between the two countries has led to a significant misunderstanding of giant sea bass population health.

A map showing high density of giant sea bass along the west coast of the U.S. and along both sides of the Baja Peninsula.
Giant sea bass live in coastal waters from northern California all the way south to the Sea of Cortez.
Arturo Ramiréz-Valdez, CC BY-ND

Different countries, different science

The giant sea bass is the largest coastal bony fish in the Northeastern Pacific. It can grow up to 9 feet (2.7 meters) long and weigh up to 700 pounds (315 kg). It lives in coastal waters from northern California to the tip of the Baja California peninsula in Mexico, including the entire Gulf of California.

In California, commercial fishing for the species began in the late 1880s. Large fish used to be very abundant across the entire range, but the fishery collapsed in the early 1970s. As a response, in 1981 the U.S. banned both commercial and recreational fishing for giant sea bass, and there are many ongoing research and population recovery efforts today.

The collapse and subsequent protection and flurry of research in the U.S. stand in stark contrast to Mexico. In Mexico, there are minimal regulations on fishing for the species, and there is almost a complete lack of data and research on it – there are only three studies on giant sea bass with any data from Mexico.

The International Union for Conservation of Nature considers giant sea bass to be a critically endangered species due to the population being “severely fragmented, leading to a continuing decline of mature individuals.” But this decision was based on a report that had no data whatsoever from Mexico. This lack of data is concerning, considering 73% of the species’ range is in Mexican waters.

This knowledge gap made me wonder if ecologists had the wrong idea about the health of giant sea bass populations.

A man standing behind a very large black fish on a scale.
Giant sea bass are a common sight at fish markets throughout Baja.
Proyecto Mero Gigante, CC BY-ND

Healthy fish in Mexico

In 2017, I led an effort to document the giant sea bass population in Mexico and look for clues to what it was in the past. At the beginning of the project, my colleagues and I feared that the records in Mexico would confirm the precarious situation of the fish in the U.S. But the reality turned out to be the opposite.

A man in orange overalls on a small blue boat sitting behind four large black fish on the deck.
Commercial fishers don’t often target giant sea bass, but catch them as bycatch when fishing for other species.
Proyecto Mero Gigante, CC BY-ND

To our surprise, we found giant sea bass everywhere in the fish markets and fishing grounds from our very first assessments. The fishmongers were never out of the fish; instead, they would ask us, “How many kilos do you need?” It was clear that for fishers in Mexico, the species is still common in the sea, and therefore, in their nets. It is still possible to find big fish up to 450 pounds 200 kilograms, and the average catch was around 26 pounds (12 kilograms).

It was fantastic to see an abundance of these fish in markets, but I also wanted to understand the fishery trends through history and how current fishing levels compared to previous years. I looked at historical and contemporary fishing records and found that the Mexican commercial fleet has caught an average of 55 tons per year over the past 60 years, and the fishery has been relatively stable over the past 20 years, with a peak in 2015 at 112 tons.

According to U.S. and Mexican records, the largest yearly catch ever recorded for giant sea bass in Mexico was 386 tons in 1933. Biologists consider a fishery to have collapsed when total catches, under the same effort, are less than 10% of the largest catches on record. So a steady trend of 55 tons per year shows that the fishery in Mexico has not collapsed. It is clear that giant sea bass populations have faced severe declines throughout their range; however, the health of the species is not as dire as thought.

Another interesting finding from my research is that the apparent collapse of the giant sea bass fishery documented in the 1970s actually began as early as 1932.

Over the first half of the 20th century, as the U.S. commercial fleet overfished U.S. waters, they began fishing in Mexican waters too – but they continued to count all catches as from the U.S. This changed in 1968 when the two governments signed the Mexico–U.S. Fisheries Agreement, limiting how much fish each country’s fleet could take from the other country’s waters. The collapse of the U.S. fishery in the 1970s was not due to a drastic reduction in fish numbers in Mexican waters, but driven by changes in fishing regulation between the U.S. and Mexico. The California fish populations had been depressed for decades, but this was hidden by fish from Mexico.

A large dark fish swimming in a kelp forest and surrounded by smaller fish.
Giant sea bass populations in Mexico have declined, but are still much healthier than researchers thought.
Meru Brito, CC BY-ND

Better data, better management

Based on my research, I believe that the giant sea bass may not qualify as a critically endangered species. My analysis of modern catch data suggests that the population of this iconic fish is likely much larger than biologists previously thought, especially in Mexico.

I am leading the next assessment for the International Union for Conservation of Nature, and now that we have accumulated better data, we can make a more informed decision that balances responsible management of the species with human needs.

I hope that our study inspires policymakers in the U.S. and Baja to start a conversation about how to manage this incredible fish in a collaborative way. But I feel our work also has larger implications. It shows how asymmetry in research and data can create significant barriers to understanding the past and present status of a species like the giant sea bass and make it harder to implement sustainable practices for the future.

[Get the best of The Conversation, every weekend. Sign up for our weekly newsletter.]The Conversation

Arturo Ramírez-Valdez, Researcher, University of California San Diego

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Climate change is causing tuna to migrate, which could spell catastrophe for the small islands that depend on them


Katherine Seto, University of Wollongong; Johann Bell, University of Wollongong; Quentin Hanich, University of Wollongong, and Simon Nicol, University of CanberraSmall Pacific Island states depend on their commercial fisheries for food supplies and economic health. But our new research shows climate change will dramatically alter tuna stocks in the tropical Pacific, with potentially severe consequences for the people who depend on them.

As climate change warms the waters of the Pacific, some tuna will be forced to migrate to the open ocean of the high seas, away from the jurisdiction of any country. The changes will affect three key tuna species: skipjack, yellowfin, and bigeye.

Pacific Island nations such as the Cook Islands and territories such as Tokelau charge foreign fishing operators to access their waters, and heavily depend on this revenue. Our research estimates the movement of tuna stocks will cause a fall in annual government revenue to some of these small island states of up to 17%.

This loss will hurt these developing economies, which need fisheries revenue to maintain essential services such as hospitals, roads and schools. The experience of Pacific Island states also bodes poorly for global climate justice more broadly.

Island states at risk

Catches from the Western and Central Pacific represent over half of all tuna produced globally. Much of this catch is taken from the waters of ten small developing island states, which are disproportionately dependent on tuna stocks for food security and economic development.

These states comprise:

  • Cook Islands
  • Federated States of Micronesia
  • Kiribati
  • Marshall Islands
  • Nauru
  • Palau
  • Papua New Guinea
  • Solomon Islands
  • Tokelau
  • Tuvalu

Their governments charge tuna fishing access fees to distant nations of between US$7.1 million (A$9.7 million) and $134 million (A$182 million), providing an average of 37% of total government revenue (ranging from 4-84%).



Tuna stocks are critical for these states’ current and future economic development, and have been sustainably managed by a cooperative agreement for decades. However, our analysis reveals this revenue, and other important benefits fisheries provide, are at risk.




Read more:
Warming oceans are changing Australia’s fishing industry


Climate change and migration

Tuna species are highly migratory – they move over large distances according to ocean conditions. The skipjack, yellowfin and bigeye tuna species are found largely within Pacific Island waters.

Concentrations of these stocks normally shift from year to year between areas further to the west in El Niño years, and those further east in La Niña years. However, under climate change, these stocks are projected to shift eastward – out of sovereign waters and into the high seas.

Under climate change, the tropical waters of the Pacific Ocean will warm further. This warming will result in a large eastward shift in the location of the edge of the Western Pacific Warm Pool (a mass of water in the western Pacific Ocean with consistently high water temperatures) and subsequently the prime fishing grounds for some tropical tuna.

This shift into areas beyond national jurisdiction would result in weaker regulation and monitoring, with parallel implications for the long-term sustainability of stocks.

Pacific Tuna: Feeling the Heat.

What our research found

Combining climate science, ecological models and economic data from the region, our research published today in Nature Sustainability shows that under strong projections of climate change, small island economies are poised to lose up to US$140 million annually by 2050, and up to 17% of annual government revenue in the case of some states.

The Intergovernmental Panel on Climate Change (IPCC) provides scenarios of various greenhouse gas concentrations, called “representative concentration pathways” (RCP). We used a higher RCP of 8.5 and a more moderate RCP of 4.5 to understand tuna movement in different emissions scenarios.




Read more:
Citizen scientist scuba divers shed light on the impact of warming oceans on marine life


In the RCP 8.5 scenario, by 2050, our model predicted the total biomass of the three species of tuna in the combined jurisdictions of the ten Pacific Island states would decrease by an average of 13%, and up to 20%.

But if emissions were kept to the lower RCP 4.5 scenario, the effects are expected to be far less pronounced, with an average decrease in biomass of just 1%.

While both climate scenarios result in average losses of both tuna catches and revenue, lower emissions scenarios lead to drastically smaller losses, highlighting the importance of climate action.

These projected losses compound the existing climate vulnerability of many Pacific Island people, who will endure some of the earliest and harshest climate realities, while being responsible for only a tiny fraction of global emissions.

Large tuna fish on the back of a fishing boat
Fishing access fees make up a large proportion of government revenue for these Pacific Island nations.
Shutterstock

What can be done?

Capping greenhouse gas emissions, and reducing them to levels aligning with the Paris Agreement, would reduce multiple climate impacts for these states, including shifting tuna stocks.

In many parts of the world, the consequences of climate change compound upon one another to create complex injustices. Our study identifies new direct and indirect implications of climate change for some of the world’s most vulnerable populations.




Read more:
The 2016 Great Barrier Reef heatwave caused widespread changes to fish populations


The Conversation


Katherine Seto, Research Fellow, University of Wollongong; Johann Bell, Visiting Professorial Fellow, University of Wollongong; Quentin Hanich, Associate Professor, University of Wollongong, and Simon Nicol, Adjunct professor, University of Canberra

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Breakthrough allows scientists to determine the age of endangered native fish using DNA


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Benjamin Mayne, CSIROIdentifying the age of animals is fundamental to wildlife management. It helps scientists know if a species is at risk of extinction and the rate at which it reproduces, as well as determining what level of fishing is sustainable.

Determining the age of fish has been difficult in the past — primarily involving extracting the inner ear bone, also known as the “otolith”. Layers of growth in the otolith are counted like rings on a tree to reveal an individual’s age. Unless a dead specimen is available, this method requires killing a fish, making it unsuitable for use on endangered populations.

However a non-lethal DNA test developed by the CSIRO enables researchers to determine fish age for three iconic and threatened Australian freshwater species: the Australian lungfish, the Murray cod and the Mary River cod. We outline the technological breakthrough in our research just published.

Our fast, accurate and cost-effective test can be adapted for other fish species. We now hope to share this method to improve the protection of wild fish populations and help promote sustainable fisheries around the world.

gloved hands cut open fish with sciessors
Traditionally, age could only be determined on a dead fish. The new method is non-lethal.
Shutterstock

Iconic species at risk

Human activity has led to the population declines of the three Australian fish species at the centre of our research.

The threatened Australian lungfish is found in rivers and lakes in southeast Queensland. It’s often referred to as a “living fossil” because its extraordinary evolutionary history stretches back more than 100 million years, before all land animals including dinosaurs.

Man-made barriers in rivers reduce the movement of water, which lowers lungfish breeding rates.

Older lungfish do not have hard otolith structures, which makes determining their age difficult. Bomb radiocarbon, which analyses carbon levels in organic matter, has been used to age Australian lungfish, but this method is too expensive to be widely used.

Australian lungfish
In the past, determining the age of Australian lungfish has been challenging.

The threatened Murray cod is Australia’s largest freshwater fish. The Mary River cod is one of Australia’s most endangered fish, found in less than 30% of its former range in Queensland’s Mary River.

Habitat destruction and overfishing are major threats to Murray cod and Mary River cod populations.

Otoliths can be used to determine age for both these cod species, however this has only been done on a population-wide scale for the more prevalent Murray cod.




Read more:
Australia’s smallest fish among 22 at risk of extinction within two decades


Mary River cod
CSIRO estimated the age of Mary River cod.

Our DNA breakthrough

When cells divide to make new cells, DNA is replicated. This can lead to DNA methylation, which involves the addition or the loss of a “methyl group” molecule at places along the DNA strand.

Research has found the level of DNA methylation is a reliable predictor of age, particularly in mammals, including humans.

To develop our test, we first worked with zebrafish. This species is useful when studying fish biology because it has a short lifespan and high reproductive rates. We took zebrafish whose ages were known, then removed a tiny clip of their fin. We then examined DNA methylation levels in the fin sample to identify the fish’s age.

Following this successful step, we transferred the method to Australian lungfish, Murray cod and Mary River cod. Again, we used fish of known ages, as well as bomb radiocarbon dating of scales and ages determined from otoliths.

We found despite the zebrafish and the study fish species being separated by millions of years of evolution, our method worked in all four species. This suggests the test can be used to predict age in many other fish species.




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Good news from the River Murray: these 2 fish species have bounced back from the Millennium Drought in record numbers


DNA strand
The test uses co-called DNA methylation to estimate age.
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A conservation management boom?

In the same way human population demographers use census data to understand and model human populations, we now have the tools to do this with animals.

We are looking to expand this DNA-based method to determine the age of the endangered eastern freshwater cod and trout cod. We will also continue to test the method across other species including reptiles and crustaceans.

This work is part of CSIRO’s ongoing efforts to use DNA to measure and monitor the environment. This includes estimating the lifespan of vertebrate species such as long-lived fish and surveying biodiversity in seawater using DNA extracted from the environment.

We envisage that in the not too distant future, these methods may be used by other researchers to better understand and manage wild animal populations.




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A new study shows an animal’s lifespan is written in the DNA. For humans, it’s 38 years


The Conversation


Benjamin Mayne, Molecular biologist and bioinformatician, CSIRO

This article is republished from The Conversation under a Creative Commons license. Read the original article.

About 500,000 Australian species are undiscovered – and scientists are on a 25-year mission to finish the job


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Kevin Thiele, The University of Western Australia and Jane Melville, Museums VictoriaHere are two quiz questions for you. How many species of animals, plants, fungi, fish, insects and other organisms live in Australia? And how many of these have been discovered and named?

To the first, the answer is we don’t really know. But the best guess of taxonomists – the scientists who discover, name, classify and document species – is that Australia’s lands, rivers, coasts and oceans probably house more than 700,000 distinct species.

On the second, taxonomists estimate almost 200,000 species have been scientifically named since Europeans first began exploring, collecting and classifying Australia’s remarkable fauna and flora.

Together, these estimates are disturbing. After more than 300 years of effort, scientists have documented fewer than one-third of Australia’s species. The remaining 70% are unknown, and essentially invisible, to science.

Taxonomists in Australia name an average 1,000 new species each year. At that rate, it will take at least 400 years to complete even a first-pass stocktake of Australia’s biodiversity.

This poor knowledge is a serious threat to Australia’s environment. And a first-of-its kind report released today shows it’s also a huge missed economic opportunity. That’s why today, Australia’s taxonomists are calling on governments, industry and the community to support an important mission: discovering and documenting all Australian species within 25 years.

Australia: a biodiversity hotspot

Biologically, Australia is one of the richest and most diverse nations on Earth – between 7% and 10% of all species on Earth occur here. It also has among the world’s highest rates of species discovery. But our understanding of biodiversity is still very, very incomplete.

Of course, First Nations peoples discovered, named and classified many species within their knowledge systems long before Europeans arrived. But we have no ready way yet to compare their knowledge with Western taxonomy.

Finding new species in Australia is not hard – there are almost certainly unnamed species of insects, spiders, mites and fungi in your backyard. Any time you take a bush holiday you’ll drive past hundreds of undiscovered species. The problem is recognising the species as new and finding the time and resources to deal with them all.

Taxonomists describe and name new species only after very careful due diligence. Every specimen must be compared with all known named species and with close relatives to ensure it is truly a new species. This often involves detailed microscopic studies and gene sequencing.

More fieldwork is often needed to collect specimens and study other species. Specimens in museums and herbaria all over the world sometimes need to be checked. After a great deal of work, new species are described in scientific papers for others to assess and review.

So why do so many species remain undiscovered? One reason is a shortage of taxonomists trained to the level needed. Another is that technologies to substantially speed up the task have only been developed in the past decade or so. And both these, of course, need appropriate levels of funding.

Of course, some groups of organisms are better known than others. In general, noticeable species – mammals, birds, plants, butterflies and the like – are fairly well documented. Most less noticeable groups – many insects, fungi, mites, spiders and marine invertebrates – remain poorly known. But even inconspicuous species are important.

Fungi, for example, are essential for maintaining our natural ecosystems and agriculture. They fertilise soils, control pests, break down litter and recycle nutrients. Without fungi, the world would literally grind to a halt. Yet, more than 90% of Australian fungi are believed to be unknown.




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How we discovered a hidden world of fungi inside the world’s biggest seed bank


fungi on log
Fungi plays an essential ecosystem role.
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Mind the knowledge gap

So why does all this matter?

First, Australia’s biodiversity is under severe and increasing threat. To manage and conserve our living organisms, we must first discover and name them.

At present, it’s likely many undocumented species are becoming extinct, invisibly, before we know they exist. Or, perhaps worse, they will be discovered and named from dead specimens in our museums long after they have gone extinct in nature.

Second, many undiscovered species are crucial in maintaining a sustainable environment for us all. Others may emerge as pests and threats in future; most species are rarely noticed until something goes wrong. Knowing so little about them is a huge risk.

Third, enormous benefits are to be gained from these invisible species, once they are known and documented. A report released today
by Deloitte Access Economics, commissioned by Taxonomy Australia, estimates a benefit to the national economy of between A$3.7 billion and A$28.9 billion if all remaining Australian species are documented.

Benefits will be greatest in biosecurity, medicine, conservation and agriculture. The report found every $1 invested in discovering all remaining Australian species will bring up to $35 of economic benefits. Such a cost-benefit analysis has never before been conducted in Australia.

The investment would cover, among other things, research infrastructure, an expanded grants program, a national effort to collect specimens of all species and new facilities for gene sequencing.




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A few months ago, science gave this rare lizard a name – and it may already be headed for extinction


Two scientists walk through wetlands holding boxes
Discovering new species often involves lots of field work.
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Mission possible

Australian taxonomists – in museums, herbaria, universities, at the CSIRO and in
government departments – have spent the last few years planning an ambitious mission to discover and document all remaining Australian species within a generation.

So, is this ambitious goal achievable, or even imaginable? Fortunately, yes.

It will involve deploying new and emerging technologies, including high-throughput robotic DNA sequencing, artificial intelligence and supercomputing. This will vastly speed up the process from collecting specimens to naming new species, while ensuring rigour and care in the science.

A national meeting of Australian taxonomists, including the young early career researchers needed to carry the mission through, was held last year. The meeting confirmed that with the right technologies and more keen and bright minds trained for the task, the rate of species discovery in Australia could be sped up by the necessary 16-fold – reducing 400 years of effort to 25 years.

With the right people, technologies and investment, we could discover all Australian species. By 2050 Australia could be the world’s first biologically mega-rich nation to have documented all our species, for the direct benefit of this and future generations.




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Hundreds of Australian lizard species are barely known to science. Many may face extinction


The Conversation


Kevin Thiele, Adjunct Assoc. Professor, The University of Western Australia and Jane Melville, Senior Curator, Terrestrial Vertebrates, Museums Victoria

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Marine life is fleeing the equator to cooler waters. History tells us this could trigger a mass extinction event


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Anthony Richardson, The University of Queensland; Chhaya Chaudhary, University of Auckland; David Schoeman, University of the Sunshine Coast, and Mark John Costello, University of AucklandThe tropical water at the equator is renowned for having the richest diversity of marine life on Earth, with vibrant coral reefs and large aggregations of tunas, sea turtles, manta rays and whale sharks. The number of marine species naturally tapers off as you head towards the poles.

Ecologists have assumed this global pattern has remained stable over recent centuries — until now. Our recent study found the ocean around the equator has already become too hot for many species to survive, and that global warming is responsible.

In other words, the global pattern is rapidly changing. And as species flee to cooler water towards the poles, it’s likely to have profound implications for marine ecosystems and human livelihoods. When the same thing happened 252 million years ago, 90% of all marine species died.

The bell curve is warping dangerously

This global pattern — where the number of species starts lower at the poles and peaks at the equator — results in a bell-shaped gradient of species richness. We looked at distribution records for nearly 50,000 marine species collected since 1955 and found a growing dip over time in this bell shape.

A chart with three overlapping lines, each representing different decades. It shows that between 1955 and 1974, the bell curve is almost flat at the top. For the lines 1975-1994 and 1995-2015, the dip gets progressively deeper, with peaks either side of the centre.
If you look at each line in this chart, you can see a slight dip in total species richness between 1955 and 1974. This deepens substantially in the following decades.
Anthony Richardson, Author provided

So, as our oceans warm, species have tracked their preferred temperatures by moving towards the poles. Although the warming at the equator of 0.6℃ over the past 50 years is relatively modest compared with warming at higher latitudes, tropical species have to move further to remain in their thermal niche compared with species elsewhere.

As ocean warming has accelerated over recent decades due to climate change, the dip around at the equator has deepened.

We predicted such a change five years ago using a modelling approach, and now we have observational evidence.




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For each of the 10 major groups of species we studied (including pelagic fish, reef fish and molluscs) that live in the water or on the seafloor, their richness either plateaued or declined slightly at latitudes with mean annual sea-surface temperatures above 20℃.

Today, species richness is greatest in the northern hemisphere in latitudes around 30°N (off southern China and Mexico) and in the south around 20°S (off northern Australia and southern Brazil).

school of tuna fish
The tropical water at the equator is renowned for having the richest diversity of marine life, including large aggregations of tuna fish.
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This has happened before

We shouldn’t be surprised global biodiversity has responded so rapidly to global warming. This has happened before, and with dramatic consequences.

252 million years ago…

At the end of the Permian geological period about 252 million years ago, global temperatures warmed by 10℃ over 30,000-60,000 years as a result of greenhouse gas emissions from volcano eruptions in Siberia.

A 2020 study of the fossils from that time shows the pronounced peak in biodiversity at the equator flattened and spread. During this mammoth rearranging of global biodiversity, 90% of all marine species were killed.

125,000 years ago…

A 2012 study showed that more recently, during the rapid warming around 125,000 years ago, there was a similar swift movement of reef corals away from the tropics, as documented in the fossil record. The result was a pattern similar to the one we describe, although there was no associated mass extinction.

Authors of the study suggested their results might foreshadow the effects of our current global warming, ominously warning there could be mass extinctions in the near future as species move into the subtropics, where they might struggle to compete and adapt.

Today…

During the last ice age, which ended around 15,000 years ago, the richness of forams (a type of hard-shelled, single-celled plankton) peaked at the equator and has been dropping there ever since. This is significant as plankton is a keystone species in the foodweb.

Our study shows that decline has accelerated in recent decades due to human-driven climate change.

The profound implications

Losing species in tropical ecosystems means ecological resilience to environmental changes is reduced, potentially compromising ecosystem persistence.

In subtropical ecosystems, species richness is increasing. This means there’ll be species invaders, novel predator-prey interactions, and new competitive relationships. For example, tropical fish moving into Sydney Harbour compete with temperate species for food and habitat.

This could result in ecosystem collapse — as was seen at the boundary between the Permian and Triassic periods — in which species go extinct and ecosystem services (such as food supplies) are permanently altered.

The changes we describe will also have profound implications for human livelihoods. For example, many tropical island nations depend on the revenue from tuna fishing fleets through the selling of licenses in their territorial waters. Highly mobile tuna species are likely to move rapidly toward the subtropics, potentially beyond sovereign waters of island nations.




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Similarly, many reef species important for artisanal fishers — and highly mobile megafauna such as whale sharks, manta rays and sea turtles that support tourism — are also likely to move toward the subtropics.

The movement of commercial and artisanal fish and marine megafauna could compromise the ability of tropical nations to meet the Sustainable Development Goals concerning zero hunger and marine life.

Is there anything we can do?

One pathway is laid out in the Paris Climate Accords and involves aggressively reducing our emissions. Other opportunities are also emerging that could help safeguard biodiversity and hopefully minimise the worst impacts of it shifting away from the equator.

Currently 2.7% of the ocean is conserved in fully or highly protected reserves. This is well short of the 10% target by 2020 under the UN Convention on Biological Diversity.

Manta ray with other fish
Manta rays and other marine megafauna leaving the equator will have a huge impact on tourism.
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But a group of 41 nations is pushing to set a new target of protecting 30% of the ocean by 2030.

This “30 by 30” target could ban seafloor mining and remove fishing in reserves that can destroy habitats and release as much carbon dioxide as global aviation. These measures would remove pressures on biodiversity and promote ecological resilience.

Designing climate-smart reserves could further protect biodiversity from future changes. For example, reserves for marine life could be placed in refugia where the climate will be stable over the foreseeable future.

We now have evidence that climate change is impacting the best-known and strongest global pattern in ecology. We should not delay actions to try to mitigate this.

This story is part of Oceans 21

Our series on the global ocean opened with five in-depth profiles. Look out for new articles on the state of our oceans in the lead-up to the UN’s next climate conference, COP26. The series is brought to you by The Conversation’s international network.




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The Conversation


Anthony Richardson, Professor, The University of Queensland; Chhaya Chaudhary, , University of Auckland; David Schoeman, Professor of Global-Change Ecology, University of the Sunshine Coast, and Mark John Costello, Professor, University of Auckland

This article is republished from The Conversation under a Creative Commons license. Read the original article.