The scientists have been able to lure tropical fish – similar to clownfish like film star Nemo – on to artificial reefs by playing recordings of fish and shrimp noises through underwater speakers. A paper in Science journal suggests the technique could be used to restock depleted fishing grounds near reefs, or to populate newly established conservation areas. The study, which focuses on damselfish and cardinalfish in the Pacific Ocean, also warns that 'unnatural' noises created by shipping and drilling may be depleting fish stocks in sensitive areas.
Previous research has shown that the larvae of coral reef fishes develop in open seas, away from reefs where predators lurk. Despite spending weeks at sea as larvae, potentially scattered over many miles, young coral reef fish eventually seek out a permanent home. A few lucky survivors make it back to their natal reef, grow into adults and produce offspring, but most do not. Studies have hinted that the young fishes' behaviour determines where they end up as much as ocean currents. The Science paper is the first to show that fish take cues from specific animal sounds – in this case, shrimps and other fish – to guide them back to their natal reefs. The tests showed that noisy artificial reefs enticed more fish than silent ones
Stephen Simpson, of the University of Edinburgh's School of Biological Sciences, who is working with scientists in Australia and New Zealand, said: "Coral reef fishes live in dangerous times because of overfishing and damage to their natural habitat. To manage fish effectively, we need to understand their behaviour, particularly during the oceanic stage of their life, when they develop as larvae. We are particularly interested in the importance of sound. Reefs are noisy environments, with the crackle of snapping shrimps and the chatter of fish set against a backdrop of wind, rain and surf, but sound travels well underwater, and fish have great hearing.
"We studied two of the most important reef fish families on noisy artificial reefs compared to silent ones. The damselfish were drawn to the high frequency noise of snapping shrimps, while the cardinalfish responded to both high and low frequency noises produced by shrimps and other fish. This study is a significant step forward in our understanding of their behaviour, which should help us to better predict how we should conserve or harvest populations of reef fishes in the future. It should also alert policy makers to the damage that human activities like drilling and shipping may have on fish stocks because they drown out the natural cues given by animals."
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