This international workshop funded by the Netherlands Ministry of Infrastructure and the Environment, IMARES Wageningen UR and TNO, was held in August 2013 with a group of 102 participants, comprised of scientists, regulators and other stakeholders. The workshop consisted of short presentations on key topics followed by group discussions focused on how new scientific information related to the effects of underwater noise on marine life influences permitting practices for human activities at sea. Also discussed were how individual countries regulate underwater noise (and grant permits) and opportunities for harmonising approaches between neighbouring countries, as well as on an international scale. The workshop was intended to build momentum towards an international exchange of information and to potentially establish a network for the regulation community.
Most of the discussions during the workshop, and consequently reported herein, are focussed on effects related to marine mammals, while aspects referring to other animal groups will be specifically indicated. Current research on noise-induced effects focuses on behavioural changes, population level outcomes, increasing the number of species for which there is existing data, and finding the best metric to describe temporary threshold shift (TTS) in animal hearing.
Large gaps in knowledge still exist. Filling these gaps is of primary imp ortance in order to provide regulators with the necessary scientific knowledge and understanding about cause-effect relationships and noise thresholds. In particular, hearing sensitivity in baleen whales remains an unsolved, but highly relevant question. New results on long-term effects of TTS raise new questions about the definition of impairment and injury. Other taxa, such as bony fishes, sharks, or invertebrate species, need to be considered as well, with many of the same questions as those raised for marine mammals. Fishes, sharks, and invertebrates are generally sensitive to particle motion, although some species are also sensitive to sound pressure. Little is known about particle motion detection by fishes, and even less is known about responses of other organisms. It is important to determine relevant thresholds for the detection of particle motion in relation to behavioural effects, as well as pressure-related physiological effects and masking in these animals.
The needs of regulators from different countries are comparable: they need reliable and understandable baseline information on cause-effect relationships. This information could be partially provided through targeted training material for regulators (and other stakeholders). These materials are not currently available. Another critical regulator need is for opportunities to speak with each other and share knowledge across wide geographic regions. Identifying the questions common among the countries/parties could help raising funds from various countries and help increasing efficiency by reducing redundancy.
Additional keys to future success were identified, including the needs to obtain commitments from the regulatory senior management and politicians, ensuring that their nations will participate (by pointing out the benefits of participating in this discussion) and will encourage participation by regulators from their agencies or institutions; invite nations who were not represented in the Budapest discussions to participate in future meetings; and raise awareness of this topic across a broad audience, including the public. In order to keep the momentum up, there are attempts underway to launch a platform for information exchange, and follow -up meetings are planned to discuss more concrete measures, as well as scientific aspects.