Acoustic release of gas bubbles to prevent cetacean entanglement in fishing nets

Cetacean interactions with commercial fishing nets have become both a global conservation issue as well as an economical concern. Not only have some populations been drastically reduced by incidental bycatch, but fishermen have also increasingly complained about an unsustainable loss of captures in certain areas, directly linked to cetacean predation.

Although acoustic deterrents appeared to be a promising solution to reduce bycatch in some areas and with some species, their general use in European waters may not be a definitive answer to the problem.

In addition to this, the large scale introduction of these acoustic sources may also worsen the noise load in certain areas already heavily exposed to artificial sounds and may negatively affect not only the species involved in the interactions, i.e. fish and mammals, but also other non commercial target species.

Based on the current knowledge of ocean acoustics, we took into account the properties of underwater sound backscattered from air bubbles to analyse their acoustic response to incident sonar waves from the bottlenose dolphin, the harbour porpoise and the orca, three of the most common cetacean species involved in fishing interactions, to study how good a reflector a bubble cloud could be and what the behavioural response of these species would be when insonified-back by their own signals.

This study is conducted with the partnership of MAREXI, and funded by the Spanish Ministry of Science and Education under the PROFIT Programme.