Coral reef fish breed more successfully if noise from motorboats is reduced, new research shows.
Scientists have introduced ‘traffic calming’ on three reefs for an entire breeding season, reducing the number of boats within 100m and reducing the speed of those within that distance.
They then tracked the breeding of fish called spiny chromis – and found that 65% of nests on calmer reefs still contained offspring at the end of the season, compared to 40% on reefs heavily frequented by motorboats.
Offspring were larger on calmer reefs and each nest also contained more offspring at the end of the season.
Aquarium tests on the same species show that noise disrupts important parental behaviors, including “fanning” eggs with their fins to ensure oxygen supply.
The research, led by the universities of Exeter and Bristol, was carried out on reefs near Lizard Island research station on Australia’s Great Barrier Reef.
“With coral reefs around the world facing multiple threats, the results of our experiment offer a way to help struggling populations,” said lead author Dr Sophie Nedelec, from the University of Exeter. .
“The simple reduction of boat noise on reefs provides much-needed relief to fish for successful breeding.
“Keeping shipping channels away from reefs, driving slowly when approaching reefs, and avoiding anchoring next to reefs offer three simple changes that any boat operator can adopt.
“These solutions empower local people to protect vulnerable ecosystems.”
Dr Nedelec added: “No one has tried a field experiment like this before.
“We monitored six reefs (three with calming traffic and three without) over an entire summer breeding season, swimming every other day along each reef to monitor the survival of 86 broods of spiny chromis in their natural habitat.”
Of 46 nests observed on reefs where traffic calming was implemented, 30 still contained offspring at the end of the breeding season. On control reefs (without traffic moderation), only 16 of 40 still contained offspring.
Co-author Dr Laura Velasquez Jimenez, from James Cook University, said: “Because spiny chromis hide their eggs in reef caves, nests are difficult to find before offspring emerge. , so we conducted a parallel study in aquaria to study embryonic development.”
In this aquarium study, some spiny chromis parents and eggs were kept with readings of natural reef sounds and others were exposed to intermittent readings of boat noise through loudspeakers.
Boat noise readings interrupted the fan, but with natural sounds the fan continued uninterrupted.
Co-author Professor Andy Radford, University of Bristol, said: “The complementary laboratory study demonstrated that these improvements in animal husbandry are really due to the limitation of noise pollution, and not to other types of disturbance caused by ships.”
The combined results suggest that reducing boat noise could have major benefits for reef fish populations, making reefs more resilient to current human-induced changes.
Cyclones and bleaching are becoming more frequent due to climate change and wreak havoc when they strike.
Finding ways to accelerate population growth after these destructive events could be the difference between decline or recovery.
However, the team points out that limiting boat traffic will not be enough to fully protect coral reefs.
Lead author Professor Steve Simpson, University of Bristol, said: “We know that reefs around the world are in trouble.
“As we try to tackle the biggest threat of climate change, we need simple solutions that reduce local threats.
“Acoustic sanctuaries can build coral reef resilience and help give reefs a better chance of recovery.”
The research, led by an international team including James Cook University, received funding from the Natural Environment Research Council.
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