A new study has reported that coral reef fish farming is done successfully if the noise from motor boats is reduced.
Researchers began a so-called “traffic rest” on three reefs for a full breeding season – reducing the number of boats within 100 m and the speed of those within that distance.
They also monitored the breeding of fish known as the spiny chromis — and found that 65% of nests on quieter reefs were still made up of offspring at the end of the season, compared to 40% on reefs with heavy motorboat traffic.
Also, the offspring were larger on quieter reefs and each nest had more offspring in the late season.
Aquarium tests conducted on the same species show that noise interrupts significant parental behavior, such as “blowing” eggs with their fins to ensure oxygenation.
The study, led by the Universities of Exeter and Bristol, was conducted on reefs adjacent to Lizard Island Research Station on Australia’s Great Barrier Reef.
With coral reefs around the world facing multiple threats, the results of our experiment provide a way to help struggling populations† Simply reducing boat noise at reefs provides fish with much-needed relief to enable successful reproduction†
dr. Sophie Nedelec, lead author of the study, University of Exeter
Nedelec added, “By moving fairways further away from reefs, moving slowly when approaching reefs, and avoiding anchoring next to reefs, there are three simple changes any boat operator can make† These solutions put the power in the hands of the local population to protect fragile ecosystems†
dr. Nedelec notes: “No one has tried such a field experiment before† We monitored six reefs (three with traffic slowing and three without) over an entire summer season, swimming past each reef every other day to track the survival of 86 spiny chromis broods in their natural habitat†
Of the 46 nests observed on reefs where traffic calming measures were applied, some still contained offspring at the end of the breeding season. On control reefs (without traffic calming effect) only 16 of the 40 still contain offspring.
Spiny chromis hide their eggs in caves in the reef, the nests are difficult to find before the offspring emerge, so we conducted a parallel study in aquariums to study embryonic development.
dr. Laura Velasquez Jimenez, study co-author, James Cook University
In this aquarium study conducted, a few spiny chromis parents and eggs were held with natural reef sound reproductions, and others were vulnerable to intermittent boat noise reproduction via loudspeakers.
Boat sound playback stopped blowing in, but natural sounds kept blowing in continuously.
The additional lab study showed that these breeding improvements are really due to noise reduction, not other types of nuisance from the boats.†
Andy Radford, co-author and professor at the University of Bristol
The joint results indicate that reducing boat noise could have significant benefits for reef fish populations. This makes reefs stronger for changes currently driven by human activity.
Cyclones and bleaching are becoming more common as a result of climate change, leading to destruction when they strike.
Determining methods of accelerating population growth after such destructive events can lead to the difference being made between fall or revival.
But the team adds that restricting boat traffic would not be enough to fully protect coral reefs.
Senior author Professor Steve Simpson, from the University of Bristol, stated: “We know reefs around the world are in trouble† As we seek to address the greatest threat of climate change, we need simple solutions that mitigate local threats† Acoustic sanctuaries can make coral reefs more resilient and give reefs a better chance of recovery†
The current study was conducted by an international team, including James Cook University. The research received funding from the Natural Environment Research Council.
Nedelec, SL, et al† (2022) Limiting the noise of motorboats on coral reefs increases the reproductive success of fish. nature communication† doi.org/10.1038/s41467-022-30332-5†
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