COVID has reached Antarctica. Scientists are extremely concerned for its wildlife



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Michelle Power, Macquarie University and Meagan Dewar, Federation University Australia

In December, Antarctica lost its status as the last continent free of COVID-19 when 36 people at the Chilean Bernardo O’Higgins research station tested positive. The station’s isolation from other bases and fewer researchers in the continent means the outbreak is now likely contained.

However, we know all too well how unpredictable — and pervasive — the virus can be. And while there’s currently less risk for humans in Antarctica, the potential for the COVID-19 virus to jump to Antarctica’s unique and already vulnerable wildlife has scientists extremely concerned.

We’re among a global team of 15 scientists who assessed the risks of the COVID-19 virus to Antarctic wildlife, and the pathways the virus could take into the fragile ecosystem. Antarctic wildlife haven’t yet been tested for the COVID-19 virus, and if it does make its way into these charismatic animals, we don’t know how it could affect them or the continent’s ecosystem stability.

A person looking at the red research station in the distance, by the ocean
Bernardo O Higgins Station in Antarctica, where 36 people tested positive to COVID-19.
Stone Monki/Wikimedia, CC BY-SA

Jumping from animals to humans, and back to animals

The COVID-19 virus is one of seven coronaviruses found in people — all have animal origins (dubbed “zoonoses”), and vary in their ability to infect different hosts. The COVID-19 virus is thought to have originated in an animal and spread to people through an unknown intermediate host, while the SARS outbreak of 2002-2004 likely came from raccoon dogs or civets.

Given the general ubiquity of coronaviruses and the rapid saturation of the global environment with the COVID-19 virus, it’s paramount we explore the risk for it to spread from people to other animals, known as “reverse zoonoses”.

The World Organisation for Animal Health is monitoring cases of the COVID-19 virus in animals. To date, only a few species around the globe have been found to be susceptible, including mink, felines (such as lions, tigers and cats), dogs and a ferret.

Whether the animal gets sick and recovers depends on the species. For example, researchers found infected adolescent cats got sick but could fight off the virus, while dogs were much more resistant.




Read more:
Can your pets get coronavirus, and can you catch it from them?


Researchers and tourists

While mink, dogs or cats are not in Antarctica, more than 100 million flying seabirds, 45% of the world’s penguin species, 50% of the world’s seal populations and 17% of the world’s whale and dolphin species inhabit the continent.

A tourist sits near a penguin and takes a photo
Tourists visit penguin roosts in large numbers.
Shutterstock

In a 2020 study, researchers ran computer simulations and found cetaceans — whales, dolphins or porpoises — have a high susceptibility of infection from the virus, based on the makeup of their genetic receptors to the virus. Seals and birds had a lower risk of infection.

We concluded that direct contact with people poses the greatest risk for spreading the virus to wildlife, with researchers more likely vectors than tourists. Researchers have closer contact with wildlife: many Antarctic species are found near research stations, and wildlife studies often require direct handling and close proximity to animals.

Tourists, however, are still a concerning vector, as they visit penguin roosts and seal haul-out sites (where seals rest or breed) in large numbers. For instance, a staggering 73,991 tourists travelled to the continent between October 2019 and April 2020, when COVID-19 was just emerging.

Each visitor to Antarctica carries millions of microbial passengers, such as bacteria, and many of these microbes are left behind when the visitors leave. Most are likely benign and probably die off. But if the pandemic has taught us anything, it takes only one powerful organism to jump hosts to cause a pandemic.

How to protect Antarctic wildlife

There are guidelines for visitors to reduce the risk of introducing infectious microbes. This includes cleaning clothes and equipment before heading to Antarctica and between animal colonies, and keeping at least five metres away from animals.

These rules are no longer enough in COVID times, and more measures must be taken.

The first and most crucial step to protect Antarctic wildlife is controlling human-to-human spread, particularly at research stations. Everyone heading to Antarctica should be tested and quarantined prior to travelling, with regular ongoing tests throughout the season. The fewer people with COVID-19 in Antarctica, the less opportunity the virus has to jump to animal hosts.

A killer whale poking its head out the water near sea ice
Cetaceans, such as orcas, are more susceptible to COVID infections than sea birds and seals.
Shutterstock

Second, close contact with wildlife should be restricted to essential scientific purposes only. All handling procedures should be re-evaluated, given how much we just don’t know about the virus.

We recommend all scientific personnel wear appropriate protective equipment (including masks) at all times when handling, or in close proximity to, Antarctic wildlife. Similar recommendations are in place for those working with wildlife in Australia.

Migrating animals that may have picked up COVID-19 from other parts of the world could also spread it to other wildlife in Antarctica. Skuas, for example, migrate to Antarctica from the South American coast, where there are enormous cases of COVID-19.




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Coronavirus: wastewater can tell us where the next outbreak will be


And then there’s the issue of sewage. Around 37% of bases release untreated sewage directly into the Antarctic ecosystem. Meanwhile, an estimated 57,000 to 114,000 litres of sewage per day is dumped from ships into the Southern Ocean.

Fragments of the COVID virus can be found in wastewater, but these fragments aren’t infectious, so sewage isn’t considered a transmission risk. However, there are other potentially dangerous microbes found in sewage that could be spread to animals, such as antibiotic-resistant bacteria.

A huge cruise ship in icy Antarctic waters
Ships dump 114,000 litres of sewage into the water, each day.
Shutterstock

We can curb the general risk of microbes from sewage if the Antarctic Treaty formally recognises microbes as invasive species and a threat to the Antarctic ecosystem. This would support better biosecurity practices and environmental control of waste.

Taking precautions

In these early stages of the pandemic, scientists are scrambling to understand complexity of COVID-19 and the virus’s characteristics. Meanwhile, the virus continues to evolve.

Until the true risk of cross-species transmission is known, precautions must be taken to reduce the risk of spread to all wildlife. We don’t want to see the human footprint becoming an epidemic among Antarctic wildlife, a scenario that can be mitigated by better processes and behaviours.




Read more:
Humans threaten the Antarctic Peninsula’s fragile ecosystem. A marine protected area is long overdue


The Conversation


Michelle Power, Associate Professor in the Department of Biological Sciences, Macquarie University and Meagan Dewar, Lecturer, Federation University Australia

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

Australia must control its killer cat problem. A major new report explains how, but doesn’t go far enough


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Sarah Legge, Australian National University; Chris Dickman, University of Sydney; Jaana Dielenberg, Charles Darwin University; John Woinarski, Charles Darwin University, and Tida Nou, The University of Queensland

Australia is teeming with cats. While cats make great pets, and can bring owners emotional, psychological and health benefits, the animals are a scourge on native wildlife.

Cats kill a staggering 1.7 billion native animals each year, and have played a major role in most of Australia’s 34 mammal extinctions. They continue to pose an extinction threat to at least another 120 species.

Long-nosed potoroo
The long-nosed potoroo is extremely vulnerable to cats.
Shutterstock

A recent parliamentary inquiry into the problem of feral and pet cats in Australia has affirmed the issue is indeed of national significance. The final report, released last week, calls for a heightened, more effective, multi-pronged and coordinated policy, management and research response.

As ecologists, we’ve collectively spent more than 50 years researching Australia’s cat dilemma. We welcome most of the report’s recommendations, but in some areas it doesn’t go far enough, missing major opportunities to make a difference.

Night curfews aren’t good enough

The report recommends Australia’s 3.8 million pet cats be subject to night-time curfews. This measure would benefit native nocturnal mammals, but won’t save birds and reptiles, which are primarily active during the day.


Wes Mountain/The Conversation, CC BY-ND

Pet cats kill 83 million native reptiles and 80 million native birds in Australia each year. From a wildlife perspective, keeping pet cats contained 24/7 is the only responsible option.

It’s clearly possible: one third of Australian pet cat owners already keep their pets contained all the time.

Stopping pet cats from roaming is also good for the cats, which live longer, safer lives when kept exclusively indoors. It would also substantially reduce the number of people falling ill from cat-dependent diseases each year.




Read more:
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Other strategies for improving pet cat management proposed in the report include pet cat registration, subsidised programs for early age desexing, public education campaigns to promote responsible pet cat ownership, and improving the consistency of rules and legislation nationally.

Cat on a windowsill
Indoor cats live longer than cats allowed to roam.
Jaana Dielenberg

The report is also unambiguously opposed to “trap-neuter-release” programs, in which un-owned cats in urban areas are desexed and then released. We agree with this finding, as these programs aren’t effective at reducing the population of stray cats, nor preventing those cats from killing wildlife and spreading disease.

We need more wildlife havens

One of the inquiry’s flagship recommendations is a national conservation project dubbed “Project Noah”. This would involve an ambitious expansion of Australia’s existing network of reserves free from introduced predators, both on islands and in mainland fenced areas. The reserves provide havens — or a fleet of “arks” — for vulnerable native wildlife.

This measure is vital. 2019 research found Australia has more than 65 native mammal species and subspecies that can’t persist, or struggle to persist, in places with even very low numbers of cats or foxes. This includes the bilby, numbat, quokka, dibbler and black-footed rock wallaby.

Boodie
Boodies used to occur across two-thirds of Australia, but now only exist within havens.
McGregor/Arid Recovery

Australia already has more than 125 havens, 100 of which are islands. These have prevented 13 mammal species from going extinct, such as boodies and greater stick-nest rats. In total, these havens have protected populations of 40 mammal species susceptible to cats and foxes.

This is a good start, but we need more investment in havens to prevent extinctions. More than 25 species are highly sensitive to cat and fox predation, but aren’t yet protected in the haven network. This includes the central rock-rat, which is more likely than not to become extinct within 20 years without new action.

What’s more, some species, such as the long-nosed potoroo, exist in just one haven. To avoid issues such as inbreeding and to ensure disasters like a fire at any single haven don’t take out an entire species, each species should be represented across several havens, in reasonable population sizes.

The report didn’t specify how the havens network should be expanded. But 2019 research found to get each species needing protection into at least three havens, Australia requires at least 35 new, strategically located islands or mainland fenced areas.

Fence with scenic hills behind
The predator proof fence at the Australian Wildlife Conservancy’s Newhaven Sanctuary, one of the largest cat- and fox-free havens on mainland Australia.
Australian Wildlife Conservancy

What about the rest of the country?

Havens cover less than 1% of Australia. So what we do in the other 99% of the landscape — including across conservation reserves like national parks — is vital.

Yet the parliamentary inquiry report lacks clear recommendations to expand cat control more broadly, including at important conservation sites such as in Kakadu National Park.

The impact of roaming pet cats on Australian wildlife.

The report reaffirms the need to cull feral cats, and to set new targets for culling, without specifying what those targets are. We agree some culling is important, especially at sites with very vulnerable threatened wildlife.

But in many parts of Australia, broad-scale habitat management is a more cost-effective way to reduce cat harm. This involves making habitat less suitable for cats and more suitable for native wildlife, for example, by reducing rabbit numbers, fire frequency and grazing by feral herbivores such as cattle and horses.

Research has shown fewer rabbits leads to fewer cats. Rabbits are a favoured prey of many cats, so they boost feral cat numbers, which then also hunt native wildlife.




Read more:
One cat, one year, 110 native animals: lock up your pet, it’s a killing machine


And cats gravitate to areas with less vegetation because it’s easier to catch prey. These areas include those with frequent fires, or where feral herbivores have reduced vegetation through grazing and trampling.

Better habitat with more vegetation gives native animals places to hide from predators, and more food and shelter. It’s a bit like giving the last little pig a house of bricks instead of trying to fist-fight the wolf.

Feral horses, such as these in Kakadu National Park, eat and damage vegetation making conditions more favourable for cats to hunt.
Jaana Dielenberg

A major step forward

Over the past two decades, Australia has slowly woken up to the damage cats cause to nature. This has led to more research, management and policy to address the problem.

Some state governments, environment groups and scientists have worked hard to develop feral cat control options, and the 2015 Australian Threatened Species Strategy did much to focus national attention and resourcing to the issue.




Read more:
Don’t let them out: 15 ways to keep your indoor cat happy


The parliamentary inquiry is a major step forward, and many recommendations are sound. But overall, its recommendations call for incremental improvement.

Australia’s laws clearly fail to provide a safety net for wildlife. The cat issue is part of a larger problem with how we manage habitat, biodiversity and threats to nature – and fixing that requires wholesale change.The Conversation

Sarah Legge, Professor, Australian National University; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; Jaana Dielenberg, University Fellow, Charles Darwin University; John Woinarski, Professor (conservation biology), Charles Darwin University, and Tida Nou, Project officer, The University of Queensland

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

The US jumps on board the electric vehicle revolution, leaving Australia in the dust



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Jake Whitehead, The University of Queensland; Dia Adhikari Smith, The University of Queensland, and Thara Philip, The University of Queensland

The Morrison government on Friday released a plan to reduce carbon emissions from Australia’s road transport sector. Controversially, it ruled out consumer incentives to encourage electric vehicle uptake. The disappointing document is not the electric vehicle jump-start the country sorely needs.

In contrast, the United States has recently gone all-in on electric vehicles. Like leaders in many developed economies, President Joe Biden will offer consumer incentives to encourage uptake of the technology. The nation’s entire government vehicle fleet will also transition to electric vehicles made in the US.

Electric vehicles are crucial to delivering the substantial emissions reductions required to reach net-zero by 2050 – a goal Prime Minister Scott Morrison now says he supports.

It begs the question: when will Australian governments wake up and support the electric vehicle revolution?

A do-nothing approach

In Australia in 2020, electric vehicles comprised just 0.6% of new vehicle sales – well below the global average of 4.2%.

Overseas, electric vehicle uptake has been boosted by consumer incentives such as tax exemptions, toll road discounts, rebates on charging stations and subsidies to reduce upfront purchase costs.

And past advice to government has stated financial incentives are the best way to get more electric vehicles on the road.

But government backbenchers, including Liberal MP Craig Kelly, have previously warned against any subsidies to make electric cars cost-competitive against traditional cars.




Read more:
Scott Morrison has embraced net-zero emissions – now it’s time to walk the talk


Releasing the government’s Future Fuels Strategy discussion paper on Friday, Energy and Emissions Reduction Minister Angus Taylor said subsidies for electric vehicles did not represent good value for money.

(As argued here, the claim is flawed because it ignores the international emissions produced by imported vehicle fuel).

The Morrison government instead plans to encourage business fleets to transition to electric vehicles, saying businesses accounted for around 40% of new light vehicle sales in 2020.

The government has also failed to implement fuel efficiency standards, despite in 2015 establishing a ministerial forum to do so.

The approach contrasts starkly with that taken by the Biden administration.

Craig Kelly struggling to open a bottle
Liberal MP Craig Kelly, pictured here struggling to open a bottle of water, opposes government subsidies to encourage electric vehicles.
Lukas Coch/AAP

Biden’s electrifying plan

Cars, buses and trucks are the
largest source of emissions in the US. To tackle this, Biden has proposed to:

And by committing to carbon-free electricity generation by 2035, the Biden administration is also ensuring renewable energy will power this electric fleet.

This combined support for electric vehicles and renewable energy is crucial if the US is to reach net zero emissions by 2050.




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Clean, green machines: the truth about electric vehicle emissions


Made in America

US companies are getting on board to avoid missing out on the electric vehicle revolution.

The day after Biden announced his fleet transition plan, General Motors (GM) – the largest US vehicle manufacturer and a major employer – announced it would stop selling fossil fuel vehicles by 2035 and be carbon-neutral by 2040.

This aligns with plans by the US states of California and Massachusetts to ban the sale of fossil fuel vehicles by 2035.

GM is serious about the transition, committing $US27 billion and planning at least 30 new electric vehicle models by 2025. And on Friday, the Ford Motor Company said it would double its investment in vehicle electrification to $US22 billion.

A General Motors ad for its electric vehicle strategy which aired during the US Superbowl.

Opportunities and challenges abound

Using government fleets to accelerate the electric vehicle transition is smart and strategic, because it:

  • allows consumers to see the technology in use

  • creates market certainty

  • encourages private fleets to transition

  • enables the development of a future second-hand electric vehicle market, once fleet vehicles are replaced.

Biden’s fleet plan includes a clear target, ensuring it stimulates the economy and supports his broader goal to create one million new US automotive jobs. Prioritising local manufacturing of vehicles, batteries and other components is key to maximising the benefits of his electric vehicle revolution.

On face value, the Morrison government’s business fleet plan has merit. But unlike the US approach, it does not involve a clear target and funding allocated to the initiative is relatively meagre.

So it’s unlikely to make much difference or put Australia on par with its international peers.

Man inspects an electric vehicle battery
Australia is well placed to capitalise on demand for electric vehicle components.
Shutterstock

Australian governments must wake up

Compounding the absence of consumer incentives to encourage uptake in Australia, some states are mulling taxing electric vehicles before the market has been established.

Our research shows this could not only delay electric vehicle uptake, but jeopardise Australia’s chances of reaching net-zero emissions by 2050.

Australia is already a world leader in building fast-charging hardware, and manufactures electric buses and trucks. We could also lead the global electric vehicle supply chain, due to our significant reserves of lithium, copper and nickel.

Despite these opportunities, the continuing lack of national leadership means the country is missing out on many economic benefits the electric vehicle revolution can bring.

Australia should adopt a Biden-inspired electric vehicle agenda. Without it, we will miss our climate targets, and the opportunity for thousands of new jobs.




Read more:
Wrong way, go back: a proposed new tax on electric vehicles is a bad idea


The Conversation


Jake Whitehead, Advance Queensland Industry Research Fellow & Tritum E-Mobility Fellow, The University of Queensland; Dia Adhikari Smith, E-Mobility Research Fellow, The University of Queensland, and Thara Philip, E-Mobility Doctoral Researcher, The University of Queensland

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

On an electric car road trip around NSW, we found range anxiety (and the need for more chargers) is real




Amelia Thorpe, UNSW; Declan Kuch, Western Sydney University, and Sophie Adams, UNSW

Replacing cars that run on fossil fuels with electric cars will be important in meeting climate goals – road transport produces more than 20% of global greenhouse gas emissions. But there are obstacles to wider uptake, particularly in Australia.

Too much of the debate about these vehicles revolves around abstract, technical calculations and assumptions about cost and benefit. Tariffs, taxes and incentives are important in shaping decisions, but the user experience is often overlooked. To better understand this we took a Tesla on a road trip from Sydney through some regional towns in New South Wales.




Read more:
The US jumps on board the electric vehicle revolution, leaving Australia in the dust


We soon found “range anxiety” is real. That’s the worry that the battery will run out of power before reaching the destination or a charging point. It’s often cited as the most important reason for reluctance to buy an electric vehicle.

Even as prices come down and hire and share options become more widespread, range anxiety about electric vehicles is hindering their wider uptake. We found it can largely be overcome through a range of strategies readily available now.

Lessons from our road trip

The first is simply to accumulate driving experience with a particular vehicle. Teslas promise a far simpler machine with fewer moving parts, but also incredibly sophisticated sensing and computational technology to help control your trip. This means you need to get a feel for the algorithms that calculate route and range.

These algorithms are black boxes – their calculations are invisible to users, only appearing as outputs like range calculations. On our trip, range forecasts were surprisingly inaccurate for crossing the Great Dividing Range, for example.




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Second, we found it very helpful to connect with other electric vehicle users and share experiences of driving. Just like any new technology, forming a community of users is a good way to gain an understanding of the vehicle’s uses and limits. Owner associations and lively online groups such as Electric Vehicles for Australia make finding fellow enthusiasts easy.

This connection can also help with the third strategy. It involves developing an understanding of how companies like Tesla control their vehicles and issue “over the air” software updates. If these specify different parameters for acceptable battery charge, that can change the vehicle’s range.

Public investment in charging network will help

Public investment in charging infrastructure could – and should – further ease range anxiety. Better planning and co-ordination are needed, too, to build on networks like the NRMA’s regional network of 50 kilowatt chargers.

electric car travelling at speed on highway
Long driving distances call for better planning and co-ordination of a nationwide charging network.
alexfan32/Shutterstock

Understanding what is involved for users is also crucial to the environmental benefits of electric vehicles. Their sustainability isn’t just a function of taxes and technologies. The practices of people driving electric cars matter too.

You learn with experience what efficient driving requires of you. You can also work out how your charging patterns could match solar generation at home, for those lucky enough to have rooftop PV panels.

These vehicles can deliver significant environmental benefits. They produce zero tailpipe emissions, reducing both local air pollution and global greenhouse gas emissions.

Regenerative braking also reduces brake particulate emissions. That’s because the electric motor operating in reverse can slow the car while recharging its battery.

Electric vehicles won’t cure all ills

Switching from internal combustion to electric cars won’t address all the problems of our current car-based system. Some, such as road congestion, could get worse.




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Road traffic will still cause deaths and injuries. Electric vehicles will still produce deadly PM2.5 particulates as long as they use conventional brakes and tyres. Many models do, providing similar driving experiences to combustion vehicles.

Congestion and the costs of providing and maintaining roads, parking and associated infrastructure will still create enormous social, economic and environmental burdens. Electric vehicles need to be part of a much wider transformation – especially in urban areas where other transport options are available.




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Rural and regional Australia can benefit too

Longer distances and lower densities make walking, cycling and public transport more challenging in rural and regional areas. Better support for electric vehicles, particularly chargers, could make a significant difference here.

These vehicles can help rural and regional areas in other ways too. Many holiday towns rely on tourist incomes but their electricity supply is at the mercy of long thin power lines that run through bushland. Electric vehicles could potentially help with this problem: when parked they can feed power back into the grid.

Tesla being charged at a rural charging point
Improving rural and regional charging networks can benefit those areas as well as the drivers of electric vehicles.
Shutterstock

Regional economic planning that supports visits by electric vehicle drivers can reduce the need to invest in energy generation or battery systems. There are huge opportunities to integrate electricity planning and the (re)building of bushfire-affected towns, which a trial in Mallacoota will explore.

Pooled together, the batteries of an all-electric national vehicle fleet could provide power equivalent to that of five Snowy 2.0s. This would boost energy security and flexibility.




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Owners of electric vehicles to be paid to plug into the grid to help avoid blackouts


In the US, President Joe Biden has announced electric vehicles will replace the entire federal fleet of 645,000 vehicles. An extra 500,000 public charging stations are to be built within a decade.

In Australia, the policy landscape is more [contested]. It’s time we caught up here.

We can start by recognising the importance of governments in the progress made internationally. Examples include the US$465 million US government loan to Tesla in 2009 to develop the landmark Model S, and Norway’s co-ordinated national approach to properly accounting for the environmental and social costs of cars. Norway’s success is now the focus of a laugh-out-loud Superbowl ad from GM, a company that in the past killed the electric car.

We need to understand users and have democratic debates about planning for charging infrastructure before we can sit back and enjoy the ride.The Conversation

Amelia Thorpe, Associate Professor in Law, UNSW; Declan Kuch, Vice Chancellor’s Research Fellow, Institute for Culture and Society, Western Sydney University, and Sophie Adams, Research Fellow, School of Humanities and Languages, UNSW

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

Under the moonlight: a little light and shade helps larval fish to grow at night



Jeffrey Shima, Author provided

Jeffrey Shima, Te Herenga Waka — Victoria University of Wellington; Craig W. Osenberg, University of Georgia; Stephen Swearer, The University of Melbourne, and Suzanne Alonzo, University of California, Santa Cruz

At night on any one of hundreds of coral reefs across the tropical Pacific, larval fish just below the sea surface are gambling on their chances of survival.

Our latest research shows the brightness of the Moon could play a major role in that struggle for survival by affecting the availability of prey and keeping predators away.

Understanding how that works could help in fisheries management, specifically the prediction of changes to harvested fish stocks that allow us to anticipate how many adult fish can be taken without destabilising the fishery.

Many fish populations experience boom-and-bust cycles largely because parents routinely produce millions of offspring that have very low, but fluctuating, survival rates.

The large number of larval fish that are produced means any environmental conditions — for example, increased nutrients — that improve survival odds even only marginally can lead to a big influx in the number of surviving offspring.

Several sixbar wrasse swim above a reef.
Adult sixbar wrasse in courtship.
Author?, Author provided

When the Sun goes down

In the past we failed to take into account the influences the night may have on fish development.

In our research we found the daily growth rates of the larvae of sixbar wrasse (Thalassoma hardwicke) around the island of Mo’orea, in French Polynesia, are strongly linked to phases of the Moon.




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Their growth appears to be maximised when the first half of the night is dark and the second half of the night is bright.

Cloudy nights obscure the Moon, and thus allowed us to check our models by contrasting growth on cloudy versus clear nights, which confirmed the effect of moonlight on growth of these fish.

Phases of the Moon

We found that on the best nights of the lunar month for sixbars, around the last Quarter Moon when the Moon rises around midnight, larval fish grew about 0.012mm a day more than average.

But on the worst nights, around the first Quarter Moon when the Moon is overhead at sunset and sets around midnight, they grew about 0.014mm a day less than average.

From First Quarter to Full Moon then Last Quarter.
Phases of the Moon from the Southern Hemisphere.
Wikimedia, CC BY-SA

For a typical larval sixbar of 37.5 days old, that means its growth is 24% more on the best night than on the worst one. This is important, as growth is inextricably linked to survival and ultimately fisheries productivity.

We think the Moon affects larval growth in this way because of how it changes the movements of deeper-dwelling animals, those that migrate into shallow water each night to hunt for food under the cover of darkness.

Zooplankton — potential prey for larval sixbars — respond quickly to the arrival of darkness, and move into the surface water to supplement the diets of sixbars.

Micronekton, such as lanternfishes, which hunt larval fishes, may take much longer to reach surface waters and seek out their prey, due to their migration from much deeper depths.

Four graphs showing different phases of the Moon and the amount of predator/prey during each phase.
Four graphs showing the larval fish (in yellow) and the amount of predator (red shading area) and prey (brown shading area) rising to the surface during each phase of he Moon.
Proceedings of the Royal Society B, Author provided

As a consequence, prey availability for sixbars in surface waters may be hindered by early nocturnal brightness while the arrival of predators may be impeded by late nocturnal brightness.

Thus, larval fish grow best when their predators are absent but their prey are abundant — around the last Quarter Moon.

In contrast, around the first Quarter Moon, prey are suppressed but predators are not, leading to the slowest growth.

During the New Moon, when the surface waters remain dark throughout the night, influxes of both prey and predators may be high, with the latter preventing the larval fish from enjoying the increased numbers of prey.

On the other hand, during the Full Moon, when surface waters are well-lit, the movement of prey and predators may be suppressed, reducing the risk to the fish but also eliminating their food.

Impact on fishing

More research is needed to quantify these lunar effects on other marine populations. But our findings to date are good news for those working to strengthen fisheries management, given that phases of the Moon are predictable and cloud cover that can modify moonlight is being measured by satellites.

A diver underwater keeping watch on one of the sixbar wrasse fish.
Observing the sixbar wrasse spawning.
Author?, Author provided

This makes the incorporation of moonlight into existing fisheries management models relatively simple.

We think this will have implications around the world, not just in the tropics. This is because the nightly upward movements of deep-water animals is ubiquitous — it is the largest mass migration of biomass on the planet, and it happens everywhere.

The suppressive effect of moonlight on this movement of potential predators and prey is also a global phenomenon.

We evaluated effects of the Moon on growth of larval temperate fish in an earlier study and found a similar effect (moonlight enhanced growth).




Read more:
Coral reefs: climate change and pesticides could conspire to crash fish populations


The effect is stronger and more nuanced in our latest study, most likely because the waters in the tropics are comparatively clear.

Our findings also hint that other factors which affect night-time illumination of the sea may disrupt marine ecosystems. This includes the reflection of artificial lights from coastal cities, suspended sediments in the water column, and changes in cloud cover due to climate change.

In the future, we may be able to harness this extra information to help forecast fish population change to better guide the management and conservation of fisheries around the world.The Conversation

Jeffrey Shima, Professor of Ecology, Te Herenga Waka — Victoria University of Wellington; Craig W. Osenberg, Professor of Ecology, University of Georgia; Stephen Swearer, Professor of Marine biology, The University of Melbourne, and Suzanne Alonzo, Professor of Ecology & Evolutionary Biology, University of California, Santa Cruz

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