Certain fish communities are loud during the day, while others are more vocal at night
Fish communication is more active in the pre-monsoon than in the post-monsoon season. Representational photo: iStock. Researchers have recorded the bustling sounds of marine organisms in coral reefs off the coast of south Goa to understand their behaviour.
Certain fish communities are loud during the day, while others are more vocal at night, noted the findings of the study published in the Journal of the Acoustical Society of America on April 27, 2023.
The researchers from the Indian Council of Scientific and Industrial Research’s National Institute of Oceanography (NIO) used hydrophones to eavesdrop on underwater organisms in a reef in the Arabian Sea. Hydrophones are a low-cost means of monitoring species.
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“If the coral reef system is healthy, fish will be there and the presence of soniferous (sound-producing) fish will generate sound. This can be monitored using simple hydrophone sensors,” Bishwajit Chakraborty, emeritus scientist, NIO, told Down To Earth.
The technology, he added, can help researchers to study the abundance, diversity and behaviour of organisms. It can also reveal how they respond to climate change and anthropogenic disturbances.
Soniferous fish represent a group of vocal vertebrates that produce sounds during various social interactions. Some 980 fish species from 133 families and 33 orders can produce active sound, according to studies.
Most fish vocalise in the frequency range of 100 Hertz (Hz) to 2,000 Hz, while shrimp use the 2,000-20,000 Hz range.
Hydrophones also pick up the sounds of wind (50-20,000 Hz) and oceanic traffic (10-10,000 Hz).
After collecting data from March 10-14, 2016, Chakraborty and his colleagues analysed the sounds using artificial intelligence. The technology compares the recorded sounds with archival information to distinguish calls coming from fish species or families.
But a lack of systematic fish sound archival facilities was a deterrent. As a result, they could not always identify most fish sounds at a species level.
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Planktivorous (predators of microscopic organisms called plankton), for example, produce sounds while feeding. The recordings were similar to archived information from the southeastern Arabian Sea and northern and western Australia.
The researchers identified 84, 69, 28 and 22 fish calls belonging to sciaenidae (a family of ray-finned fish), terapon theraps (an omnivorous species), planktivorous and type A (unknown fish), respectively.
Sciaenidae, Planktivorous and the unknown type A produced sounds between 14.15-19.30 and 22.45-23.00, 00.35-2.45 hours, respectively.
These organisms take shifts: Some active during the day, others at night. This is due to the diurnal effect (a pattern that recurs every 24 hours). “It is connected to sunrise (twilight) and sunset timings, which controls the fish behaviour or movement,” Chakraborty explained.
Further, fish communication is more active in the pre-monsoon than in the post-monsoon season, Chakraborty said. Mating activities of fish are dominant in the pre-monsoon period.
Hydrophones pave the way for long-term studies, crucial in examining how marine life responds to climate change and anthropogenic activities.
“For example, most fish are ectothermic, which means their activities are fully controlled by temperature. We need to have long-term data to understand the impact,” Chakraborty said.
However, hydrophones are not widely used in India. “They are not very expensive. So it should not be difficult for the Ministry of Earth Sciences to deploy the technology widely and for a long-term,” he added.
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