SHASHWAT GUPTA RAY
While the impact of temperature change on land is easily ascertained by various indicators like behavioural pattern of living beings, very little is known about the same when it comes to the situation underwater.
Now, a study by National Institute of Oceanography (NIO) Goa, has found that variation in fish sound is directly linked to temperature change happening underwater.
The team of scientists at NIO led by CSIR-Emeritus Scientist The underwater sound intensity and dominant frequency caused by fish calls fluctuates as water temperatures change, and the pulse repetition rate decreased when the water temperature increases conducted study of passive sound waves generated by marine species underwater in three shallow water sites in Goa - Off Britona in Mandovi estuary, In Grande Island in Zuari estuary, off Mormugao Port and Sal River off Betul.
The findings have been published in the Journal of the Acoustical Society of America. The study is titled Characterizing three shallow-water locations off Goa, India, using passive acoustic data.
“We had few notable observations in our analyses. Off Britona in Mandovi estuary, correlation coefficient of 88-67% is observed between the Sound Pressure Level (SPL) of Toadfish sound with respect to the temperature. In Grande Island in Zuari estuary, maximum correlation coefficient of 80% is observed between the SPL of Tiger Perch, whereas in Sal River off Betul, correlation coefficient of 84% is observed between the SPL of background sounds with respect to the wind speed,” said Bishwajit Chakraborty, Scientist Emeritus at NIO and an authority on marine or hydro-acoustics.
This means that underwater sound intensity and dominant frequency caused by fish calls increases as water temperatures rises, and the pulse repetition rate decreases when the water temperature increases.
“When wind becomes dominant, SPL is related to wind. SPL consists of fish sound as well as geophony from wind. That time fish sound SPL becomes insignificant compared to wind. Therefore, relationship shows SPL versus wind dominant,” the senior scientist said.
“The study results suggested that passive acoustics is a vital tool for understanding the biological components in relation to the environmental conditions,” added Chakraborty, who is the lead author of the study.
Underwater acoustics is the science of sound waves in the water that has become an essential tool for underwater remote sensing.
“We have also analysed data of Seahorse feeding click non-linearity using the Artificial Intelligence method, which was published in Journal of Acoustical Society America (American Institute of Physics).Further, we discovered the Humpback whale (Megaptera novaeangliae) sound from Grande Island and published it in the Bioacoustics journal,” Dr Chakraborty said. By analysing passive acoustic recordings, it is possible to discriminate and identify different animal species and to calculate the relative number of animals present within the measurement range.
Currently CSIR-NIO is busy in acquisition and analyses of passive acoustic data along with the other ancillary systems to carry out multi-parameter studies.
“However, long term passive acoustic data acquisition is needed to relate among fish sound and climate,” he said.