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Fish On Acid Lose Fear Of Predators

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Coral reef fishes exposed to acid oceans lose their sense of smell – and their sense of caution – and are more likely to fall prey to natural enemies, according to new research in Nature Climate Change.

The finding is based on observations of the behaviour of four species at a reef off the coasts of Papua New Guinea where natural carbon dioxide seeps out of the rock, and confirms a series of other such studies in the last year.

A cool volcanic discharge in the reef has served as a natural laboratory for years: water in the region reaches an average pH of 7.8. This standard measure of acidity is co-incidentally the level predicted for all the world’s oceans by 2100, as atmospheric carbon dioxide levels continue to rise, according to the Intergovernmental Panel on Climate Change.

Australian and US scientists observed the fishy behaviour from a boat moored above the reef, and also tested the fish on board the vessel. What they observed was that, away from the volcanic bubbles of carbon dioxide, in conditions of more normal ocean chemistry, damsel fish and cardinal fish seemed able to smell predators and stayed in sheltered places in the reef to avoid becoming prey.

Fish from the waters richer in carbonic acid seemed not to sense the presence of predators, and were more likely to venture into dangerous waters.

After a sudden scare that sent all the fish racing for cover, the fish from the bubble reef ventured forth much sooner. In normal circumstances, such fish spend 80% of their time under cover.

The bubble reef fish spent at most only 12% of their time in hiding. Mortality accordingly was five times higher.
“Their sense of smell was acutely affected in CO2-rich waters in ways that gravely threaten their survival,” said Alistair Cheal of the Australian Institute of Marine Science.

“We were able to test long-term realistic effects in this environment,” said another author, Danielle Dixson of the Georgia Institute of Technology in the US. “One problem with ocean acidification research is that it’s all laboratory-based, or you’re testing something that’s going to happen in 100 years’ time with fish that are from the present day, which is not actually accurate.”

The reasoning is that the change in pH levels disrupts a neuroreceptor in the fishes’ brains and affects faculties or alters behaviour. Similar experiments with Californian rockfish have demonstrated much the same effect.

But increased acidification of the oceans is also likely to affect shellfish and corals in other ways, and research in the Great Barrier Reef region of Australia has documented a dramatic behaviour change in a jumping snail that suggested impaired decision-making capability as pH levels alter.

Sea water is already 30% more acidic that it was at the start of the Industrial Revolution 200 years ago. The rate of change is at least 100 times faster than at any time in the last 650,000 years.

The bubbling waters of the reef under test are not unique – such localized carbonic acid seeps occur in many places all over the world – and the fact that predators might find easy pickings in such places makes no real difference to population levels in the vastness of the rest of the ocean. But such experiments raise the question: can ecosystems adapt to changing water chemistry?

“Continuous exposure does not reduce the effect of high CO2 on behaviour in natural reef habitat and this could be a serious problem for fish communities in the future when ocean acidification becomes widespread as a result of continued uptake of anthropogenic CO2 emissions,” the authors conclude.

 

Source: www.truthdig.com

Marine Life & Conservation

The Big Shark Pledge: Shark Trust’s new campaign kicks off with a call for support

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With the ink still drying on last week’s landmark listing of nearly 100 species of sharks on Appendix II of CITES, the Shark Trust insists that this is not the time for shark conservation to take a break. The UK-based NGO this week launches its biggest-ever concerted campaign to tackle the overfishing of oceanic sharks. They are calling on people across the world to join the call for stricter controls on high seas fisheries.

The Big Shark Pledge is at the heart of an ambitious set of campaign actions. Working to secure science-based catch limits on all sharks and rays affected by the international high seas fishing fleet. The pledge will build the largest campaigning community in shark and ray conservation history to support a raft of policy actions over the vital years ahead.

Many of our best known and much-loved sharks make their home on the high seas. In our shared ocean, these oceanic sharks and rays face a very real threat from a huge international fleet of industrial-scale fishing vessels. Research published in early 2021 confirmed that over three-quarters of oceanic sharks and rays are now at risk of extinction due to the destructive impact of overfishing. They have declined by 71% over the last 50 years.

The Shark Trust is celebrating its 25th Anniversary this year and has a long history of securing positive changes for sharks, skates and rays. The Big Shark Pledge will build on the success of their NoLimits? campaign which underpinned landmark catch limits on Blue Sharks and Shortfin Mako in the North Atlantic.

While the listing of so many species on the CITES trade agreement is certainly a positive step, there remains a huge challenge in ensuring that sustainable practices are embedded in international fisheries.” says Shark Trust Director of conservation, Ali Hood. “Sharks on the high seas face extraordinary pressure from excessive fishing practices. This has to be addressed through international agreements such as those secured for Blues and makos.”

There is hope and a feeling of momentum in the shark conservation community. Just last week, in addition to the new CITES listings, the Shark Trust, working with partners in the Shark League, secured the first-ever international quota for South Atlantic Mako at ICCAT meeting in Portugal. The new campaign from the Shark Trust aims to push forwards from here, engaging a wave of support through the Big Shark Pledge to bolster policy action.

This will be a long-term international and collaborative effort. Forging a pathway to rebuild populations of high-seas sharks and rays. By putting science at the heart of shark conservation and fisheries management. And making the vital changes needed to set populations on the road to recovery.

Shark Trust CEO Paul Cox says of the Big Shark Pledge “It’s designed to give everyone who cares about the future of sharks the chance to add their voice to effective and proven conservation action. By adding their name to the Pledge, supporters will be given opportunities to apply pressure at key moments to influence change.

Click here to sign the Big Shark Pledge

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Miscellaneous Blogs

Jeff chats to… Craig Waller, Underwater Lighting Technician on Black Panther: Wakanda Forever (Watch Video)

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In this exclusive Zoom interview, Jeff Goodman, Scubaverse Editor-at-Large, chats to Craig Waller, Underwater Lighting Technician on Black Panther: Wakanda Forever. Craig is a Key Grip and Lighting Director with 10,000s of hours of Set Experience.

In Craig’s own words:

I started my career when I was in my first year of college.  I always had that creative side of the brain that needed to be followed as a career.  I thought that would be in designing engineering pieces but wasn’t happy about the idea of an office cubicle and drafting table.

I accidentally found my way onto a big commercial job for a week and decided “THIS IS WHAT I WANT TO DO”.   I made it my career after that. This is a quick list of recent and big projects in my 35 yrs of TV / Film / Photography.

Most Recently:

  • “Black Panther 2” – UW Lighting Technician / 2nd Unit Underwater Team
  • “Stranger Things” Season 4 – UW Lighting Technician / 2nd Unit Underwater Team
  • “Suicide Squad 2” – UW Gaffer / 2nd Unit Underwater Team
  • NASCAR / FOX Sports 1 – Network TV Lighting Director – 7 years / 700 races of Live BIG track TV shows
  • 10,000s of commercials / music videos / tv shows

I started diving when I was 18 years old with my OW and then AOW with PADI. I was diving with lots of friends in the late 80s and early 90s and then moved onto Kayaking. I got my daughter into diving when she turned 14 and have picked up where I left off.

I have approx 5000 dives now and spend most of my free time diving.

Here are my certs:

  • OW – AOW 1989
  • Adv Nitrox / Deco 2020
  • Cavern – Intro Cave 2021
  • CCR Tech – Fathom – 2021

You can find out more at www.craigwaller.com


Rather listen to a podcast? Listen to the audio HERE on the new Scubaverse podcast channel at Anchor FM.

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