Curious Kids: how would the disappearance of anglerfish affect our environment?



Anglerfish have an enlarged fin overhanging their eyes and their mouth that acts as a lure – much like bait on a fisherman’s line.
Shutterstock

Andy Davis, University of Wollongong

Curious Kids is a series for children. Send your question to curiouskids@theconversation.edu.au. You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.


How would the disappearance of anglerfish affect our environment? – Bella, age 6, Sydney.


As I am sure you know, anglerfish live deep in the ocean. The females have an enlarged fin overhanging their eyes and their mouth that acts as a lure – much like bait on a fishing line – and this explains their name. (“Angling” is a method of fishing.)

The fact is we understand very little about the deep sea and how its inhabitants, including anglerfish, will respond to change. In fact, more people have walked on the Moon than have been to the bottom of the ocean.

But I will do my best to answer your question.




Read more:
Curious Kids: how do creatures living in the deep sea stay alive given the pressure?


The food web

Close your eyes and imagine a spider’s web. All parts of it are connected, and if a bug gets tangled in one part, it can cause a completely different part of the web to wobble or break.

It helps to remember that all species are interconnected via something called the “food web”. The food web is not a real web like a spider’s web. It’s just a way of thinking about how species are connected to each other. Basically, the food web tells us who eats whom.

If you make a change to one part of the food web, that can have an ripple effect that can cause changes on another part of the web.

Here’s an example of a food web (not every animal is included in this one, but you get the idea).
Shutterstock

Less of one animal can mean more of another

Anglerfish usually eat small fish, as well as relatives of shrimp.

It is likely that if all the anglerfish in the ocean disappeared, their prey would explode in number and another predator would then “step in” to replace them.

And any species that likes to eat the anglerfish would have to start eating another species instead – or risk dying out.

At the height of the whaling industry, about 100 years ago, whales nearly disappeared. That meant that the number of krill (the tiny animals that whales eat) exploded, providing a feast for other animals that also eat krill – such as seals. That is how a food web works.

Weird and wonderful

There are around 200 different types of anglerfish. Although one giant species grows to over a metre, most anglerfish are tiny – less than 10cm long.

Only female anglerfish have lures. These lures often glow in the dark, thanks to the bio-luminescent bacteria inside them, which presents a tempting (but fake) meal to their unsuspecting prey.

Anglerfish don’t form large schools like many other fish and this represents a problem for them – they need to find a mate. The tiny males have found a solution: if they do happen to find a female, they grasp onto her with their mouths and never let go.

These males tap into the females’ blood stream and never have to eat again. Scientists call this behaviour parasitic. Sometimes more than one male can be attached to a single female. Imagine someone’s father being 100 times smaller than their mother and being permanently attached to her.

Nature is truly weird and wonderful.

This picture shows the larger female has two smaller parasitic males attached to her body to fertilise her eggs.
Shutterstock



Read more:
Curious Kids: How was the ocean formed? Where did all the water come from?


Threats

Among the biggest problems for a lot of fish species are disease and overfishing by humans. But it’s highly unlikely that these threats could wipe out anglerfish.

Anglerfish are found between 300 and several thousand metres of water. At this depth, it is constantly dark and the water is cold.

As they live in such deep water and do not form schools, they are not targeted by fishermen, a common threat for many shallow water fish.

And anglerfish are so widely spread across the world’s oceans that any disease is highly unlikely to spread among them.

There is one threat that might affect angler fish – the threat of global warming. Temperatures in the deep ocean are very stable, they simply don’t change much.

Anglerfish live their entire lives at depth with near constant temperatures; hence even small shifts in temperature may affect them. It remains unclear whether increasing temperatures really will threaten angler fish – only time will tell.


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CC BY-ND

Please tell us your name, age and which city you live in. We won’t be able to answer every question but we will do our best.The Conversation

Andy Davis, Director – Institute for Conservation Biology and Environmental Management, University of Wollongong

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

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We wrote the report for the minister on fish deaths in the lower Darling – here’s why it could happen again


Robert Vertessy, University of Melbourne; Fran Sheldon, Griffith University; Lee Baumgartner, Charles Sturt University; Nick Bond, La Trobe University, and Simon Mitrovic, University of Technology Sydney

Over the recent summer, three significant fish death events occurred in the lower Darling River near Menindee, New South Wales. Species involved included Murray Cod, Silver Perch, Golden Perch and Bony Herring, with deaths estimated to be in the range of hundreds of thousands to over a million fish. These events were a serious ecological shock to the lower Darling region.

Our report for the Minister for Agriculture and Water Resources examines the causes of these events and recommend actions to mitigate the potential for repeat events in the future.

The final report has just been released, summarising what we found and what we recommend.

Causes of the fish deaths

High-flow events in the Darling River in 2012 and 2016 filled the Menindee Lakes and offered opportunities for substantial fish breeding, further aided by the targeted use of environmental water.

The result was very large numbers of fish in the lakes, river channels and weir pools around Menindee. After the lake-filling rains of late 2016, two very dry years ensued, resulting in very low inflows into the Barwon-Darling river.

As the supply of water dried up, the river became a series of disconnected and shrinking pools. As the extremely hot and dry conditions in late 2018 took hold, the large population of fish around Menindee became concentrated within weir pools.

Hot weather, low rainfall and low flows provided ideal conditions for algal blooms and thermal stratification in the weir pools, resulting in very low oxygen concentrations within the bottom waters.

With the large fish population now isolated to the oxygenated surface waters of the pools, all that was needed for the fatal blow was a trigger for the water profile to mix. Such a trigger arrived on three separate occasions, with changes in the weather that brought sudden drops in temperature and increased wind that caused sudden turnover of the low-oxygen bottom waters.

Summary of the multiple causes of the 2018-19 fish death events in the lower Darling river.

With the fish already stressed by high temperatures, they were now unable to gain enough oxygen from the water to breathe, and a very large number of them died. As we write, the situation in the lower Darling remains dire, and there is a risk of further fish deaths if there are no significant inflows to the river.

Fish deaths caused by these sorts of turnover events are not uncommon, but the conditions outlined above made these events unusually dramatic.

So, how did such adverse conditions arise in the lower Darling river and how might we avoid their reoccurrence? We’ve examined four influencing factors: climate, water management, lake operations, and fish mobility.

Key influencing factors

We found that the fish death events in the lower Darling were preceded and affected by exceptional climatic conditions.

Inflows to the water storages in the northern Basin over 2017-18 were the second lowest for any two-year period on record. Most of the Murray-Darling Basin experienced its hottest summer on record, exemplified by the town of Bourke breaking a new heatwave record for NSW, with 21 consecutive days with a maximum temperature above 40℃.

We concluded that climate change amplified these conditions and will likely result in more severe droughts in the future.

Changes in the water access arrangements in the Barwon–Darling River, made just prior to the commencement of the Basin Plan in 2012, exacerbated the effects of the drought. These changes enhanced the ability of irrigators to access water during low flow periods, meaning fewer flow pulses make it down the river to periodically reconnect and replenish isolated waterholes that provide permanent refuge habitats for fish during drought.

We conclude that the Lake Menindee scheme had been operated according to established protocols, and was appropriately conservative given the emerging drought conditions. But low connectivity in the lower Darling resulted in poor water quality and restricted mobility for fish.

Recommended policy and management actions

Given the right mix of policy and management actions, Basin governments can significantly reduce the risks of further fish death events and promote the recovery of affected fish populations.

The Basin Plan is delivering positive environmental outcomes and more benefits will accrue once the plan is fully implemented. But more needs to be done to enhance river connectivity and protect low flows, first flushes and environmental flow releases in the Barwon-Darling river.

Drought resilience in the lower Darling can be enhanced by reconfiguring the Lake Menindee Water Savings Project, modifying the current Menindee Lakes operating rules and purchasing high security water entitlements from horticultural enterprises in the region.

In Australia, water entitlements are the rights to a share of the available water resource in any season. Irrigators get less (or no) water in dry (or extremely dry) years.

A high-security water entitlement is one with a high chance of receiving the full water allocation. In some systems, although not all, this is expected to happen 95 per cent of the time. And these high-security entitlements are the most valuable and sought after.

Fish mobility can be enhanced by removing barriers to movement and adding fish passageways.

It would be beneficial for environmental water holders to place more of their focus on sustaining fish populations through drought sequences.

The river models that governments use to plan water sharing need to be updated more regularly to accurately represent the state of Basin development, configured to run on a whole-of-basin basis, and improved to more faithfully represent low flow conditions.

There are large gaps in water quality monitoring, metering of water extractions and basic hydro-ecologic knowledge that should be filled.

Risk assessments need to be undertaken to identify likely fish death event hot spots and inform future emergency response plans.

All of these initiatives need to be complemented by more sophisticated and reliable assessments of the impacts of climate change on water security across the Basin.

Governments must accelerate action

Responding to the lower Darling fish deaths in a prompt and substantial manner provides governments an opportunity to redress some of the broader concerns around the management of the Basin.

To do so, Basin governments must increase their political, bureaucratic and budgetary support for high value reforms and programs, particularly in the northern Basin.

All of our recommendations can be implemented within the current macro-settings of the Basin Plan and do not require a revisiting of the challenging socio-political process required to define Sustainable Diversion Limits (SDLs).

Successful implementation will require a commitment to authentic collaboration between governments, traditional owners, local communities, and sustained input from the science community.


The authors would like to acknowledge the contribution of Daren Barma, Director of Barma Water Consulting, to this article.

A version of this article has been published in Pursuit.The Conversation

Robert Vertessy, Enterprise Professor, University of Melbourne; Fran Sheldon, Professor, Australian Rivers Institute, Griffith University, Griffith University; Lee Baumgartner, Associate Research Professor (Fisheries and River Management), Institute for Land, Water, and Society, Charles Sturt University; Nick Bond, Professor of Freshwater Ecology and Director of the Centre for Freshwater Ecosystems, La Trobe University, and Simon Mitrovic, Associate Professor, University of Technology Sydney

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

More fish, more fishing: why strategic marine park placement is a win-win



File 20190325 36267 6gisnm.jpg?ixlib=rb 1.1
Marine parks are good for fish – especially if they’re in the right areas.
Epstock/Shutterstock

Kerstin Jantke, University of Hamburg; Alienor Chauvenet, Griffith University; Hugh Possingham, The University of Queensland; James Allan, The University of Queensland; James Watson, The University of Queensland, and Kendall Jones, The University of Queensland

Australia has some of the most spectacular marine ecosystems on the planet – including, of course, the world-famous Great Barrier Reef. Many of these places are safe in protected areas, and support a myriad of leisure activities such as recreational fishing, diving and surfing. No wonder eight in ten Aussies live near the beach.

Yet threats to marine ecosystems are becoming more intense and widespread the world over. New maps show that only 13% of the oceans are still truly wild. Industrial fishing now covers an area four times that of agriculture, including the farthest reaches of international waters. Marine protected areas that restrict harmful activities are some of the last places where marine species can escape. They also support healthy fisheries and increase the ability of coral reefs to resist bleaching.




Read more:
Most recreational fishers in Australia support marine sanctuaries


One hundred and ninety-six nations, including Australia, agreed to international conservation targets under the United Nations Convention on Biological Diversity. One target calls for nations to protect at least 10% of the world’s oceans. An important but often overlooked aspect of this target is the requirement to protect a portion of each of Earth’s unique marine ecosystems.

How are we tracking?

The world is on course to achieve the 10% target by 2020, with more than 7.5% of the ocean already protected. However, our research shows that many marine protected areas are located poorly, leaving many ecosystems underprotected or not protected at all.

What’s more, this inefficient placement of marine parks has an unnecessary impact on fishers. While marine reserves typically improve fisheries’ profitability in the long run, they need to be placed in the most effective locations.

We found that since 1982, the year nations first agreed on international conservation targets, an area of the ocean almost three times the size of Australia has been designated as protected areas in national waters. This is an impressive 20-fold increase on the amount of protection that was in place beforehand.

But when we looked at specific marine ecosystems, we found that half of them fall short of the target level of protection, and that ten ecosystems are entirely unprotected. For example, the Guinea Current off the tropical West African coast has no marine protected areas, and thus nowhere for its wildlife to exist free from human pressure. Other unprotected ecosystems include the Malvinas Current off the southeast coast of South America, Southeast Madagascar, and the North Pacific Transitional off Canada’s west coast.

Marine park coverage of global ecosystems. Light grey: more than 10% protection; dark grey: less than 10% protection; red: zero protection.
Author provided

Australia performs comparatively well, with more than 3 million square km of marine reserves covering 41% of its national waters. Australia’s Coral Sea Marine Park is one of the largest marine protected areas in the world, at 1 million km². However, a recent study by our research group found that several unique ecosystems in Australia’s northern and eastern waters are lacking protection.

Furthermore, the federal government’s plan to halve the area of strict “no-take” protection inside marine parks does not bode well for the future.

How much better can we do?

To assess the scope for improvement to the world’s marine parks, we predicted how the protected area network could have been expanded from 1982.

With a bit more strategic planning since 1982, the world would only need to conserve 10% of national waters to protect all marine ecosystems at the 10% level. If we had planned strategically from as recently as 2011, we would only need to conserve 13% of national waters. If we plan strategically from now on, we will need to protect more than 16% of national waters.

If nations had planned strategically since 1982, the world’s marine protected area network could be a third smaller than today, cost half as much, and still meet the international target of protecting 10% of every ecosystem. In other words, we could have much more comprehensive and less costly marine protection today if planning had been more strategic over the past few decades.

The lack of strategic planning in previous marine park expansions is a lost opportunity for conservation. We could have met international conservation targets long ago, with far lower costs to people – measured in terms of a short-term loss of fishing catch inside new protected areas.

This is not to discount the progress made in marine conservation over the past three decades. The massive increase of marine protected areas, from a few sites in 1982, to more than 3 million km² today, is one of Australia’s greatest conservation success stories. However, it is important to recognise where we could have done better, so we can improve in the future.

Australia’s marine park network.
Author provided

This is also not to discount protected areas. They are important but can be placed better. Furthermore, long-term increases in fish populations often outweigh the short-term cost to fisheries of no-take protected areas.

Two steps to get back on track

In 2020, nations will negotiate new conservation targets for 2020-30 at a UN summit in China. Targets are expected to increase above the current 10% of every nation’s marine area.

We urge governments to rigorously assess their progress towards conservation targets so far. When the targets increase, we suggest they take a tactical approach from the outset. This will deliver better outcomes for nature conservation, and have less short-term impact on the fishing industry.




Read more:
More than 1,200 scientists urge rethink on Australia’s marine park plans


Strategic planning is only one prerequisite for marine protected areas to effectively protect unique and threatened species, habitats and ecosystems. Governments also need to ensure protected areas are well funded and properly managed.

These steps will give protected areas the best shot at halting the threats driving species to extinction and ecosystems to collapse. It also means these incredible places will remain available for us and future generations to enjoy.The Conversation

Kerstin Jantke, Postdoctoral Researcher on conservation biology, University of Hamburg; Alienor Chauvenet, Lecturer, Griffith University; Hugh Possingham, Professor, The University of Queensland; James Allan, Postdoctoral research fellow, School of Biological Sciences, The University of Queensland; James Watson, Professor, The University of Queensland, and Kendall Jones, PhD candidate, Geography, Planning and Environmental Management, The University of Queensland

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

An end to endings: how to stop more Australian species going extinct



File 20190305 48435 o1z6b8.jpg?ixlib=rb 1.1

John Gerrard Keulemans. Published by Muséum national d’histoire naturelle (France)

John Woinarski, Charles Darwin University; Sarah Legge, Australian National University, and Stephen Garnett, Charles Darwin University

This is part of a major series called Advancing Australia, in which leading academics examine the key issues facing Australia in the lead-up to the 2019 federal election and beyond. Read the other pieces in the series here.


We need nature. It gives us inspiration, health, resources, life. But we are losing it. Extinction is the most acute and irreversible manifestation of this loss.

Australian species have suffered at a disproportionate rate. Far more mammal species have become extinct in Australia than in any other country over the past 200 years.

The thylacine is the most recognised and mourned of our lost species, but the lesser bilby has gone, so too the pig-footed bandicoot, the Toolache wallaby, the white-footed rabbit-rat, along with many other mammals that lived only in Australia. The paradise parrot has joined them, the robust white-eye, the King Island emu, the Christmas Island forest skink, the southern gastric-brooding frog, the Phillip Island glory pea, and at least another 100 species that were part of the fabric of this land, part of what made Australia distinctive.

And that’s just the tally for known extinctions. Many more have been lost without ever being named. Still others hover in the graveyard – we’re not sure whether they linger or are gone.




Read more:
What makes some species more likely to go extinct?


The losses continue: three Australian vertebrate species became extinct in the past decade. Most of the factors that caused the losses remain unchecked, and new threats are appearing, intensifying, expanding. Many species persist only in slivers of their former range and in a fraction of their previous abundance, and the long-established momentum of their decline will soon take them over the brink.

The toolache wallaby is just one of Australia’s many extinct species.
John Gould, F.R.S., Mammals of Australia, Vol. II Plate 19, London, 1863

Unnecessarily extinct

These losses need not have happened. Almost all were predictable and preventable. They represent failures in our duty of care, legislation, policy and management. They give witness to, and warn us about, the malaise of our land and waters.

How do we staunch the wound and maintain Australia’s wildlife? It’s a problem with many facets and no single solution. Here we provide ten recommendations, based on an underlying recognition that more extinctions will be inevitable unless we treat nature as part of the essence of this country, rather than as a dispensable tangent, an economic externality.

  1. We should commit to preventing any more extinctions. As a society, we need to treat our nature with more respect – our plants and animals have lived in this place for hundreds of thousands, often millions, of years. They are integral to this country. We should not deny them their existence.

  2. We should craft an intergenerational social contract. We have been gifted an extraordinary nature. We have an obligation to pass to following generations a world as full of wonder, beauty and diversity as our generation has inherited.

  3. We should highlight our respect for, and obligation to, nature in our constitution, just as that fusty document could be refreshed and some of its deficiencies redressed through the Uluru Statement from the Heart. Those drafting the blueprint for the way our country is governed gave little or no heed to its nature. A constitution is more than a simple administrative rule book. Countries such as Ecuador, Palau and Bhutan have constitutions that commit to caring for their natural legacy and recognise that society and nature are interdependent.

  4. We should build a generation-scale funding commitment and long-term vision to escape the fickle, futile, three-year cycle of contested government funding. Environmental challenges in Australia are deeply ingrained and longstanding, and the conservation response and its resourcing need to be implemented on a scale of decades.

  5. As Paul Keating stated in his landmark Redfern speech, we should all see Australia through Aboriginal eyes – more deeply feel the way the country’s heart beats; become part of the land; fit into the landscape. This can happen through teaching curricula, through reverting to Indigenous names for landmarks, through reinvigorating Indigenous land management, and through pervasive cultural respect.

  6. We need to live within our environmental limits – constraining the use of water, soil and other natural resources to levels that are sustainable, restraining population growth and setting a positive example to the world in our efforts to minimise climate change.

  7. We need to celebrate and learn from our successes. There are now many examples of how good management and investments can help threatened species recover. We are capable of reversing our mismanagement.

  8. Funding to prevent extinctions is woefully inadequate, of course, and needs to be increased. The budgeting is opaque, but the Australian government spends about A$200 million a year on the conservation of threatened species, about 10% of what the US government outlays for its own threatened species. Understandably, our American counterparts are more successful. For context, Australians spend about A$4 billion a year caring for pet cats.

  9. Environmental law needs strengthening. Too much is discretionary and enforcement is patchy. We suggest tightening the accountability for environmental failures, including extinction. Should species die out, formal inquests should be mandatory to learn the necessary lessons and make systemic improvements.

  10. We need to enhance our environmental research, management and monitoring capability. Many threatened species remain poorly known and most are not adequately monitored. This makes it is hard to measure progress in response to management, or the speed of their collapse towards extinction.




Read more:
Eulogy for a seastar, Australia’s first recorded marine extinction


Extinction is not inevitable. It is a failure, potentially even a crime – a theft from the future that is entirely preventable. We can and should prevent extinctions, and safeguard and celebrate the diversity of Australian life.The Conversation

John Woinarski, Professor (conservation biology), Charles Darwin University; Sarah Legge, Professor, Australian National University, and Stephen Garnett, Professor of Conservation and Sustainable Livelihoods, Charles Darwin University

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

It’s fish on ice, as frozen zoos make a last-ditch attempt to prevent extinction


Nicola Marie Rivers, Monash University

Twenty-six of the forty-six fish species known to live in the Murray-Darling basin are listed as rare or threatened. Recent fish kills in the iconic river system are a grim reminder of how quickly things can take a turn for the worst.

A sudden drop in population size can push a species towards extinction, but there may be hope for resurrection. Frozen zoos store genetic material from endangered species and are preparing to make new individuals if an extinction occurs.




Read more:
Cryopreservation: the field of possibilities


Unfortunately, poor response to freezing has hindered the introduction of fish into frozen zoos in the past. Now new techniques may provide them safe passage.

Ice ice baby

A frozen zoo, also known as a biobank or cryobank, stores cryopreserved or “frozen” cells from endangered species. The primary purpose of a frozen zoo is to provide a backup of endangered life on Earth allowing us to restore extinct species.

Reproductive cells, such as sperm, oocytes (eggs) and embryos, are cooled to -196ºC, at which point all cellular function is paused. When a sample is needed, the cells are warmed and used in breeding programs to produce new individuals, or to study their DNA to determine genetic relationships with other species.

There are several cryobanking facilities in Australia, including the Australian Frozen Zoo (where I work), the CryoDiversity Bank and the Ian Potter Australian Wildlife Biobank, as well as private collections. These cryobanks safeguard some of Australia’s most unique wildlife including the greater bilby, the golden bandicoot, and the yellow-footed rock wallaby as well as other exotic species such as the black rhino and orangutans.

Internationally, frozen zoos are working together to build a “Noah’s Ark” of frozen tissue. The Frozen Ark project, established in 2004 at the University of Nottingham, now consists of over 5,000 species housed in 22 facilities across the globe.

The Manchurian trout, or lenok, is the only fish successfully reproduced through cryopreservation and surrogacy.
National Institute of Ecology via Wikimedia, CC BY

Less love for fish

As more and more species move into frozen zoos, fish are at risk of being left out. Despite years of research, no long-term survival has been reported in fish eggs or embryos after cryopreservation. However, precursors of sperm and eggs known as gonial cells found in the developing embryo or the ovary or testis of adult fish have been preserved successfully in several species including brown trout, rainbow trout, tench and goby.

By freezing these precursory cells, we now have a viable method of storing fish genetics but, unlike eggs and sperm, the cells are not mature and cannot be used to produce offspring in this form.

To transform the cells into sperm and eggs, they are transplanted into a surrogate fish. Donor cells are injected into the surrogate where they follow instructions from surrounding cells which tell them where to go and when and how to make sperm or eggs.

Once the surrogate is sexually mature they can mate and produce offspring that are direct decedents of the endangered species the donor cells were originally collected from. In a way, we are hijacking the reproductive biology of the surrogate species. By selecting surrogates that are prolific breeders we can essentially “mass produce” sperm and eggs from an endangered species, potentially producing more offspring than it would have been able to within its own lifetime.

Cell surrogacy has been successful in sturgeon, rainbow trout and zebrafish.

The combination of cryopreservation and surrogacy in conservation is promising but has only successfully been used in one endangered species so far, the Manchurian trout.

Not a get-out-of-conservation card

The “store now, save later” strategy of frozen zoos sounds simple but alas it is not. The methods needed to reproduce many species from frozen tissue are still being developed and may take years to perfect. The cost of maintaining frozen collections and developing methods of resurrection could divert funding from preventative conservation efforts.

Even if de-extinction is possible, there could be problems. The Australian landscape is evolving – temperatures fluctuate, habitats change, new predators and diseases are being introduced. Extinction is a consequence of failing to adapt to these changes. Reintroducing a species into the same hostile environment that lead to its demise may be a fool’s errand. How can we ensure reintroduced animals will thrive in an environment they may no longer be suited for?

Reducing human impact on the natural environment and actively protecting threatened species will be far easier than trying to resurrect them once they are gone. In the case of the Murray Darling Basin, reversing the damage done and developing policies that ensure its long-term protection will take time that endangered species may not have.




Read more:
I’ve always wondered: does anyone my age have any chance of living for centuries?


Frozen zoos are an insurance policy, and we don’t want to have to use them. But if we fail in our fight against extinction, we will be glad we made the investment in frozen zoos when we had the chance.The Conversation

Nicola Marie Rivers, PhD Candidate, Monash University

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

Flash photography doesn’t harm seahorses – but don’t touch


Maarten De Brauwer, Curtin University; Benjamin John Saunders, Curtin University, and Tanika Cian Shalders, Curtin University

We all enjoy watching animals, whether they’re our own pets, birds in the garden, or elephants on a safari during our holidays. People take pictures during many of these wildlife encounters, but not all of these photographic episodes are harmless.

There is no shortage of stories where the quest for the perfect animal picture results in wildlife harassment. Just taking photos is believed to cause harm in some cases – flash photography is banned in many aquariums as a result.

But it’s not always clear how bright camera flashes affect eyes that are so different from our own. Our latest research, published in Nature Scientific Reports, shows that flash photography does not damage the eyes of seahorses, but touching seahorses and other fish can alter their behaviour.




Read more:
New map shows that only 13% of the oceans are still truly wild


Look but don’t touch

In the ocean it is often easier to get close to your subject than on land. Slow-moving species such as seahorses rely on camouflage rather than flight responses. This makes it very easy for divers to approach within touching distance of the animals.

Previous research has shown that many divers cannot resist touching animals to encourage them to move so as to get a better shot. Additionally, the high-powered strobes used by keen underwater photographers frequently raise questions about the welfare of the animal being photographed. Do they cause eye damage or even blindness?

A researcher photographing a ghost pipefish.
© Luke Gordon

Aquariums all around the world have taken well-meaning precautionary action. Most of us will have seen the signs that prohibit the use of flash photography.

Similarly, a variety of guidelines and laws exist in the scuba-diving community. In the United Kingdom, flash photography is prohibited around seahorses. Dive centres around the world have guidelines that include prohibiting flash or limiting the number of flashes per fish.

While all these guidelines are well-intended, none are based on scientific research. Proof of any damage is lacking. Our research investigated the effects of flash photography on slow-moving fish using three different experiments.

What our research found

During the first experiment we tested how different fish react to the typical behaviour of scuba-diving photographers. The results showed very clearly that touching has a very strong effect on seahorses, frogfishes and ghost pipefishes. The fish moved much more, either by turning away from the diver, or by swimming away to escape the poorly behaving divers. Flash photography, on the other hand, had no more effect than the presence of a diver simply watching the fishes.

For slow-moving fishes, every extra movement they make means a huge expense of energy. In the wild, seahorses need to hunt almost non-stop due to their primitive digestive system, so frequent interruptions by divers could lead to chronic stress or malnutrition.

Researchers tested the effect of high-strobe flashes on frogfish.
Author provided

The goal of the second experiment was to test how seahorses react to flash without humans present. To do this we kept 36 West Australian seahorses (Hippocampus subelongatus) in the aquarium facility at Curtin University. During the experiment we fed the seahorses with artemia (“sea monkeys”) and tested for changes in their behaviour, including how successful seahorses were at catching their prey while being flashed with underwater camera strobes.




Read more:
Now you see us: how casting an eerie glow on fish can help count and conserve them


An important caveat to this experiment: the underwater strobes we used were much stronger than the flashes of normal cameras or phones. The strobes were used at maximum strength, which is not usually done while photographing small animals at close range. So our results represent a worst-case scenario that is unlikely to happen in the real world.

The conclusive, yet somewhat surprising, result of this experiment was that even the highest flash treatment did not affect the feeding success of the seahorses. “Unflashed” seahorses spent just as much time hunting and catching prey as the flashed seahorses. These results are important, as they show that flashing a seahorse is not likely to change the short-term hunting success (or food intake) of seahorses.

Scuba divers should always avoid touching animals.
sanc0460/Flickr, CC BY

We only observed a difference in the highest flash treatment (four flashes per minute, for ten minutes). Seahorses in this group spent less time resting and sometimes showed “startled” reactions. These reactions looked like the start of an escape reaction, but since the seahorses were in an aquarium, escape was impossible. In the ocean or a large aquarium seahorses would simply move away, which would end the disturbance.

Our last experiment tested if seahorses indeed “go blind” by being exposed to strong flashes. In scientific lingo: we tested if flash photography caused any “pathomorphological” impacts. To do this we euthanised (following strict ethical protocols) some of the unflashed and highly flashed seahorses from the previous experiments. The eyes of the seahorses were then investigated to look for any potential damage.

The results? We found no effects in any of the variables we tested. After more than 4,600 flashes, we can confidently say that the seahorses in our experiments suffered no negative consequences to their visual system.

What this means for scuba divers

A potential explanation as to why flash has no negative impact is the ripple effect caused by sunlight focusing through waves or wavelets on a sunny day. These bands of light are of a very short duration, but very high intensity (up to 100 times stronger than without the ripple effect). Fish living in such conditions would have evolved to deal with such rapidly changing light conditions.

This of course raises the question: would our results be the same for deep-water species? That’s a question for another study, perhaps.




Read more:
Genes reveal how the seahorse got its snout and became a great father


So what does this mean for aquariums and scuba diving? We really should focus on not touching animals, rather than worrying about the flash.

Flash photography does not make seahorses blind or stop them from catching their prey. The strobes we used had a higher intensity than those usually used by aquarium visitors or divers, so it is highly unlikely that normal flashes will cause any damage. Touching, on the other hand, has a big effect on the well-being of marine life, so scuba divers should always keep their hands to themselves.The Conversation

Maarten De Brauwer, PhD-candidate in Marine Ecology, Curtin University; Benjamin John Saunders, Lecturer / Research fellow in Marine Ecology, Curtin University, and Tanika Cian Shalders, Marine Scientist, Curtin University

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

How did the fish cross the road? Our invention helps them get to the other side of a culvert



File 20180924 129868 4v1wjx.jpg?ixlib=rb 1.1
When a stream enters a culvert, the flow can be concentrated so much that water flows incredibly fast. So fast, in fact, that small and juvenile fish are unable to swim against the flow and are prevented from reaching where they need to go to eat, reproduce or find safety.
Shutterstock

Jabin Watson, The University of Queensland; Craig E. Franklin, The University of Queensland; Harriet Goodrich, University of Exeter; Jaana Dielenberg, The University of Queensland, and Rebecca L. Cramp, The University of Queensland

Fish need to move to find food, escape predators and reach suitable habitat for reproduction. Too often, however, human activities get in the way. Dams, weirs and culverts (the tunnels and drains often found under roads) can create barriers that fragment habitats, isolating fish populations.

An Australian innovation, however, promises to help dwindling fish populations in Australia and worldwide. Our solution, recently described in Ecological Engineering, tackles one of the greatest impediments to fish migration in Australia: culverts.

A culvert crisis in our waterways

Freshwater ecosystems are one of the most heavily impacted by human activities.

Many freshwater species, such as the iconic barramundi, start their life as larvae in estuaries, then as small juveniles they make mammoth upstream migrations to freshwater habitats. In fact, about half of the freshwater fish species in southeast Australia need to migrate as part of their life cycle.

When fish are unable to pass human-made barriers, the decline in populations can be huge. For example, in the Murray-Darling Basin where there are thousands of barriers and flows are highly regulated, fish numbers are estimated to be at only 10% of pre-European numbers.

In New South Wales alone, there are more than 4,000 human-made barriers to fish passage. Over half of these are culverts. Culverts are most often installed to allow roads to cross waterways. They are designed to move water under the road, which they do quite efficiently, but often with no consideration of the requirements of the animals that live there.

When a stream enters a culvert, the flow can be concentrated so much that water flows incredibly fast. So fast, in fact, that small and juvenile fish are unable to swim against the flow and are prevented from reaching where they need to go to eat, reproduce or find safety.

A map of human-made barriers to fish passage in NSW. Image: Fisheries NSW.

Many current design ‘fixes’ come with problems

The problem culverts pose for fish is now well acknowledged by fisheries managers, and as a result efforts to make culverts fish-friendly are now widespread.

Where space allows, these new fish passage solutions can resemble a natural stream, where rocks of various sizes are added to break up the flow. Alternatively, artificial baffles (barriers to break up and slow the flow) are also commonly attached to the walls of the tunnel.

These designs do have some drawbacks. They may suit some fish sizes and species, but not all. They can be expensive to install. They also tend to catch debris, which increases maintenance costs and the risk of flooding upstream during high flow events.

A box culvert running under a road.
Shutterstock

Using physics to find a new solution

We took a new approach that harnesses a property of fluid mechanics that scientists call the “boundary layer”. When a fluid moves over a solid surface, friction causes the water to slow down next to the surface. This thin layer of slower-moving water is called the boundary layer.

Where two surfaces meet, such as in the corner of a square culvert, the boundary layers of the bed and wall merge. This creates a small area of slower-moving water – the “reduced velocity zone” – right in the corner. This is quite small, but little fish can still use it and are very good at finding it.

We wanted to expand this zone (to accommodate a wider range of fish sizes) and slow the water in it further.

So, we added a third surface, generating three boundary layers that then joined. This was done by adding a square beam running the length of the channel wall, close to the floor. The boundary layers of the floor, wall and bottom surface of the beam merged to create a reduced velocity channel along the side of the main flow.

In this GIF to the right hand side, the reduced velocity zone is revealed by adding a fluorescent dye, which lingers in the slower flowing water under the square beam we added to the channel.

Testing our design in a 12 metre channel (or flume) found that water velocity in the zone below the beam was slowed by up to 30%. For small fish, this is a huge reduction.

In tests, we focused on small-bodied species, or juveniles of larger growing species, because these are considered the weakest swimming size class and most vulnerable to high water velocities created within culverts. Every species tested saw significant improvements in their ability to swim and traverse up the channel.

All of the species benefited, regardless of their body shape or swimming style.

The GIF on the right hand side here shows a juvenile Murray cod swimming upstream using the reduced velocity zone we created by adding the beam.

Creating a slower-flowing zone

Our novel fish passage design is highly effective, yet very simple. It’s a square beam installed along the length of a culvert wall, so it’s easy to incorporate into new structures and cheap to retrofit into existing culverts.

It is also much less likely to trap debris than baffles or rocks embedded in the floor of a culvert.

This is a totally new approach that has the potential for widespread application, helping to restore the connectivity of freshwater fish populations here in Australia, and overseas.

A Crimson-spotted rainbowfish navigates the fast flow by swimming under the beam we added to channel.
Harriet Goodrich, Author provided
You can see the beam more clearly here. A Crimson-spotted rainbowfish swims under the beam we added to slow the water flow in that area.
Harriet Goodrich, Author provided

More research lies ahead. We’re hoping that by optimising the dimensions of the beam we can get even more fish through the channels, with even greater ease. We’re also planning field testing to check our laboratory findings work in the real world.

Freshwater biodiversity is greatest in the tropics. Here, developing countries are having drastic impacts on their freshwater ecosystems. The simplicity of this design may make it an affordable approach to help maintain and restore habitat connectivity in developing regions.

Matthew Gordos from NSW Fisheries contributed to this article.The Conversation

Jabin Watson, Postdoctoral researcher, The University of Queensland; Craig E. Franklin, Professor in Zoology, The University of Queensland; Harriet Goodrich, PhD student, University of Exeter; Jaana Dielenberg, Science Communication Manager, The University of Queensland, and Rebecca L. Cramp, Senior Research Fellow, The University of Queensland

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