Making noise: research on reef fish bioacoustics leads to new technologies that could aid in restoring fish populations

Research that has revealed the role of natural sound cues in the orientation and settlement of coral reef fish has helped in the development of a new device to help attract post-larval fish to marine areas for restocking. Six prototypes of the device, which uses sound to attract fish, have been developed and tested in three countries by Ecocean, a global leader in ecosystem restoration who are developing technologies for the capture and culture of post-larval fish.

The research, conducted by Dr Steve Simpson, a NERC Knowledge Exchange Fellow and Senior Lecturer in Marine Biology and Global Change at the University of Exeter, has shown that inhabitants on coral reefs produce a wealth of noises that many marine animals – such as corals, fish and crustaceans – use as cues during important phases of their life cycle. This information has subsequently shed light on how human-made noise can mask or disrupt these natural signals.

While it has been suggested that anthropogenic noise has an adverse effect on marine mammals, the potential harm to fish and invertebrates, particularly in terms of disrupting natural sound cues, had not been considered. As well as helping in the development of Ecocean’s device, Simpson’s findings have increased global recognition of the potential detrimental impacts of anthropogenic noise in the marine environment, and have provided evidence in the establishment of international guidelines and regional campaigns to manage marine noise.

Over the last decade, Simpson and his colleagues have provided the first clear demonstration that the settlement-stage of numerous coral reef fish species are attracted to reef sounds and that they establish a connection to these sounds very early in their development. Clownfish embryos, for example, respond to noise as early as three days old. After reef fish hatch, most species spend days to weeks developing in the open ocean. When it is time for them to settle back to a reef, it makes sense that they could be attracted to the sounds they experienced as an embryo as it was a place their parents were able to successfully live and reproduce.

Further investigations by Simpson and his colleagues found that adult reef fish also orientate toward reef noise – preferentially selecting frequencies that are produced by other fish as the vocalise.

Ecocean, a French-based company, approached Simpson in 2007. Gilles Lecaillon, co-founder and President of Ecocean, had read Simpson’s research and wanted to test incorporating sound attraction into Ecocean's existing open ocean live capture light traps.

“Although we had a lot of expertise in larval fish attraction, we had no idea about underwater noise,” said Lecaillon. “Steve really brought all his knowledge to the project, and it was his sound technologies that we incorporated into the electronics of our traps”.

Over a period of four months in the Philippines, Simpson and his students helped test and perfect the prototype of the new trap, called SAFE, although due to the cost of constructing the SAFE devices, Ecocean realized they would not be not affordable for large scale deployment in the developing world. Instead, Lecaillon is now testing the SAFE device to attract post-larval fish for restocking purposes.

“As a result of the collaboration with Steve, we are now looking at using sound in our ecological restoration efforts aimed at boosting recruitment of fish to particular locations in the Mediterranean,” said Lecaillon.