Marine acoustics research could help restore coral reefs
Published on: 20 November 2014
Research looking at the role of natural sound cues in the orientation and settlement of coral reef fish has helped in the development of a new device that may help attract post-larval fish to marine areas that are being restocked.
Six prototypes of the device, which uses sound to attract the fish, have been developed and tested in three countries by Ecocean, a global leader in developing technologies for the post-larval capture and culture of fish.
Dr Steve Simpson, a Natural Environment Research Council Knowledge Exchange Fellow and Senior Lecturer in Marine Biology and Global Change at the University of Exeter, conducted the research. He has shown coral reefs have a wealth of natural noises many marine animals – such as corals, fish and crustaceans - use as cues during different parts of their life cycle. This information has shed light on how human-made noise can mask or disrupt these natural signals.
While it was known anthropogenic noise had an adverse effect on marine mammals, the potential harm to fish and invertebrates had not been considered. As well as helping in the development of Ecocean’s device, Dr Simpson’s findings have increased global recognition of the potential detrimental impacts of anthropogenic noise in the marine environment, providing evidence in the establishment of international guidelines and regional campaigns to manage marine noise.
Over the last decade, Dr 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. In the above video, you can see how Dr Simpson and colleagues assessed the best methods for gathering this, and other data.
Dr Simpson explained: “We got the idea fish might be attracted by noise because they arrive as larval fish when reefs are at their noisiest – we know this from navy recording surveys in open water.”
To investigate, Dr Simpson and his colleagues ran a number of experiments. The team built models for both fish movement and sound propagation in a laboratory setting to complement the open water results. This enabled the team to better understand how marine life behaves under noisy conditions in coral reefs.
Clownfish embryos, for example, respond to reef noise as early as three days old. After reef fish hatch, many species spend some time floating about in the open ocean. When it is time for them to settle on a reef, it makes sense they would be attracted to sounds they heard as an embryo as it was a place their parents were able to successfully live and reproduce. Further investigation found adult reef fish are also oriented toward reef noise - preferentially selecting frequencies produced by invertebrates such as snapping shrimp.
Having established sound as an orientation cue, Dr Simpson examined its importance in terms of survivorship of settling larvae. He found individuals with poorly-developed auditory systems encounter greater difficulty in detecting suitable settlement habitats and may even suffer increased rates of mortality when the acoustic environment is disturbed by anthropogenic noise.
Ecocean approached Dr Simpson in 2007. Gilles Lecaillon, Co-founder and President of Ecocean, had read Simpson’s research and wanted to look at incorporating sound attraction into Ecocean's existing open ocean live capture light traps.
He said: “Although we had a lot of expertise in larval fish attraction, we had no idea about underwater noise. Steve really brought all his knowledge to the project, and it was his sound technologies that we incorporated into the housing of our traps”.
Over a period of four months in the Philippines, Dr Simpson helped test and perfect the prototype of the new trap, called SAFE; however, due to the cost of constructing the SAFE devices, Ecocean deemed them to be not profitable for large scale deployment in the developing world. Instead, Lecaillon has plans to use the SAFE device to attract post-larval fish for restocking purposes.
Lecaillon concluded: “As a result of the collaboration with Dr Simpson, we are now looking at using sound in our ecological restoration efforts aimed at boosting recruitment of fish to particular regions of the Mediterranean.”