Loud underwater noises such as explosions are known to be harmful to nearby fish; however, a recent review published in the journal Trends in Ecology and Evolution has highlighted the potential importance of long-term exposure to more moderate sound levels.
Researchers from Leiden University in the Netherlands claim that the rise in underwater noise levels from artificial sources, such as vessels, coastal activities and offshore wind farms, may have increasing implications for fish behaviour, communication and breeding.
Recent studies with Lake Victoria cichlids by the same group of scientists showed for the first time that courtship sounds can influence the mate choices of fish. By recording the sounds produced by male Pundamilia nyererei cichlids and then broadcasting them through underwater speakers, the researchers showed that female cichlids preferred male fish that were kept in compartments where courtship calls were played.
In each test, two male P. nyererei cichlids with equal colouration were confined to separate compartments at opposite ends of the same tank. The audio recordings were then broadcast from only one of these compartments. After listening to the sounds, female cichlids nearly always chose to approach and interact with the males that were associated with the courtship calls.
The bright colouration of many cichlids plays an important role in mate selection but, according to these experiments published in the journal Behavioral Ecology, it now seems that sounds are also influential in cichlid reproduction.
These findings are among the latest to highlight the importance of underwater sounds. With fish seemingly using sounds for various communication purposes and coral larvae now known to move towards reef noises, the potential impact of underwater noise pollution could be serious for whole ecosystems. Although the scale of the behavioural and physiological effects on fish remains unknown, it is clear that further studies are required to investigate the impact of widespread increases in underwater sounds generated by humans.
For more information see the review: Slabbekoorn H, Bouton N, van Opzeeland I, Coers A, ten Cate C, Popper AN. (2010) A noisy spring: the impact of globally rising underwater sound levels on fish. Trends Ecol. Evol. doi:10.1016/j.tree.2010.04.005
For more information on the P. nyererei experiments see the paper: Verzijden MN, van Heusden J, Bouton N, Witte F, ten Cate C, Slabbekoorn H. (2010) Sounds of male Lake Victoria cichlids vary within and between species and affect female mate preferences. Behav. Ecol. 21(3) 548-555.