Scientists eavesdrop on fish chatter
BY EAVESDROPPING ON THE ETHEREAL songs of whales and dolphins, scientists have learnt much about their behaviour. Now experts are turning their attention to the sounds of fish. Deciphering such chatter could help estimate population numbers and mating behaviours, researchers from Curtin University in Perth announced this week.
Scientists already knew that some fish communicate with sound, but discovering new choruses is cause for excitement, says lead researcher and marine biologist Miles Parsons. “These sounds are definitely interesting. The number of different calls and sounds produced by fish is amazing.”
More than 300 species of fish are believed to vocalise, says Miles – mostly at a lower frequency compared with other marine creatures such as dolphins, which click and whistle, but at a higher frequency than blue or humpback whales.
Eavesdropping
Many fish use their sonic muscle, which runs the length of the body, to vibrate their adjacent swim bladder. This creates a drum roll sound. But for mulloway, their sonic muscle twitches so quickly that the sound resembles the pulsating croaks of frogs.
Listen to the sounds of a mulloway
Miles and colleagues plan to deploy new underwater recorders, to listen in on the sounds of commercial species such as mulloway (or jewfish), in WA’s Swan River and Blackwood River.
“Technology has advanced such that near-continuous recording of sound can be made remotely for periods of months to years,” he says. “For mulloway, it would be great to get to an assessment of actual numbers… in terms of dhufish, if I could record them making a sound I’ll be bouncing off walls.”
The researchers aim to determine what triggers specific calls and predict where and when spawning will occur. Recordings in different locations can be used to identify conditions which favour reproduction, and establish which spawning grounds should be protected.
Vulnerability
The study will extend previous research on mulloway and focus on other
commercially important seafood species. These include snapper, black
bream and the poorly understood dhufish. Miles adds that the technique is significant in that it doesn’t interfere with the fish, particularly the mulloway, which can be susceptible to handling stress. Current methods for assessing fish populations require tagging and recapturing.
Professor Geoff Jones, a marine biologist at James Cook University in Townsville, applauds the non-intrusive technique: “It will definitely help in understanding how sound is used to communicate and will work on almost any kind of marine fish.”
He hopes that the research will be used to understand other aspects of behaviour such as how coral reef fish use sounds to find habitat.
