[OANNES Foro] Experts said they have found a way to entice young fish back to degraded reefs: acoustic enrichment

[Mario Cabrejos]

With global heating damaging corals worldwide, experts find potential tool
in 'acoustic enrichment' to recolonise reefs

Healthy coral sounds lure fish back to abandoned reefs, study finds 

 <https://www.theguardian.com/profile/nicola-davis> Nicola Davis

29 Nov 2019 

https://www.theguardian.com/environment/2019/nov/29/sonic-youth-healthy-reef
-sounds-lure-young-fish-to-degraded-areas?CMP=share_btn_tw&utm_source=Nature
+Briefing&utm_campaign=6cddda34dd-briefing-dy-20191206&utm_medium=email&utm_
term=0_c9dfd39373-6cddda34dd-42095803

Playing sounds of a healthy coral reef can attract fish back to reefs that
have become degraded and abandoned, researchers have found.

Global heating together with factors such as pollution are causing
<https://www.theguardian.com/environment/2019/oct/25/coral-cover-around-popu
lar-great-barrier-reef-islands-has-almost-halved> widespread damage to coral
and harming delicate reef ecosystems.

Reefs offer a home to a plethora of fish species, some of which play roles
including cleaning the reef and recycling nutrients. However, previous
research has shown degraded reefs sound and smell less attractive to young
fish, meaning populations around them dwindle in what scientists fear could
be a negative spiral to silence.

But now experts said they have found a way to entice young fish back to
degraded reefs, offering a way to potentially speed their recovery.

"[We thought] if one of the things that a degraded reef is missing is its
sounds, well, that is something that on a local level we can replace and if
we do we might pull in some fish and we might kickstart a recovery a little
quicker," Tim Gordon, first author of the latest study from the University
of Exeter, told the Guardian.

Writing in the journal  <https://www.nature.com/articles/s41467-019-13186-2>
Nature Communications, the researchers reported how they created 33 patches
of dead coral rubble and placed these at locations around Australia's
northern
<https://www.theguardian.com/environment/2019/aug/30/great-barrier-reef-outl
ook-now-very-poor-australian-government-review-says> Great Barrier Reef in
water a few metres deep.

On 11 of the patches, the team played the sounds of a healthy reef at night
through loudspeakers, starting shortly before sunset and ending just after
sunrise - when fish are known to turn up and settle at reefs.

Healthy reefs, said Gordon, are bustling places. "The first thing that
strikes you is this really loud crackle sound - it is almost like static on
the radio, or some people describe it like frying bacon, and that is the
sound of thousands and thousands of snapping shrimp, all clicking their
claws," he said, adding that fish make noises ranging from grunts to hums,
buzzes and whoops.

On the other 22 patches no sounds were played - although in half of these a
dummy speaker was present.

After 40 days, the team deconstructed the patches and looked at the fish
living on the coral rubble. The results revealed that there were twice as
many young fish living on the patches where the sounds were played than in
either type of patch without such sounds, while the diversity of species was
50% greater where recordings were played.

What's more, the team found the influx of fish came from every level of the
food chain, from those that eat seaweed to those that prey on other fish -
something Gordon said is important, since the different types play different
roles on a coral reef.

The researchers said the recordings could be helping to lure young fish to
the degraded reefs either by making fish aware that the reef is there, or by
making it more likely that fish will settle there once they turn up.

While they said there is more work to do, including unpicking which
particular sounds might be behind the effect, whether different sounds might
be needed for different reef habitats, and how sounds might affect adult
fish, they said the approach has promise in speeding up reef recovery -
although it should be combined with other techniques to boost the habitat.

Gordon stressed the importance of tackling the original source of reef
damage, whether from warming oceans or blast fishing.

"It is very important to be realistic about this - this is potentially a
useful tool for attracting fish towards areas of degraded habitat but it is
not a way of solving the coral reef crisis; it is not a way of bringing back
a whole reef to life on its own," he said.

Dr Catherine Head of the Zoological Society of London and the University of
Oxford, who was not involved in the study, agreed: "Using acoustic
enrichment to help recolonise degraded reefs with essential reef fish is a
novel tool which can add to the reef conservation toolbox," she said.

But, she added: "Our biggest tool in the fight for coral reefs is the 2016
Paris climate change agreement to curb global CO2 emissions, and we must
continue to put pressure on governments to fulfil this agreement alongside
doing our bit to reduce our own carbon footprints."

 

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