- Author
- Periodical, Semaphore
- Subjects
- Ship design and development, Naval technology
- Tags
-
- RAN Ships
- None noted.
- Publication
- June 2008 edition of the Naval Historical Review (all rights reserved)
Beaked whales are acknowledged as potentially threatened by underwater sound. A number of multiple strandings of beaked whales have occurred coincident with naval use of active sonar in the northern hemisphere, and once during a seismic survey of the Gulf of California. Of these events, strandings in the Canary Islands and a highly publicised stranding in the Bahamas have galvanised public and interest group attention to ensure that active sonar is used in a manner that avoids similar incidents in future.
Deepest diving species
Beaked whales are amongst the most poorly understood of all whale species. They are relatively small, elusive, generally do not congregate in large numbers, and their principal habitats often lie well offshore. Beaked whales have been observed in most southern waters of Australia from New South Wales to southwest Western Australia. They are unique in that they hunt for squid in deep continental slope waters, and are the deepest diving of all air breathing species, recorded at depths exceeding 2,000 metres, and able to breath-hold for periods in excess of a staggering 80 minutes. Scientific understanding of the physiology of beaked whales is poor, unsurprising when they are commonly exposed to pressures of over 200 atmospheres and significant oxygen deficits during a single dive.
Fright and flight response
The actual cause of these strandings remains unclear, but a number of theories have been suggested to explain a potential mechanism for injury. The most plausible of these imply a change in diving behaviour leading to symptoms of ‘decompression sickness’ or induction of stress through a fright and flight response to the sound. The difficulties in understanding and managing these risks are compounded by recent evidence that beaked whales hear quite poorly at the frequencies used by naval anti-submarine sonars.
A stranding of melon headed whales during the 2004 Rim of the Pacific (RIMPAC) exercise off Hawaii influenced the US Navy to seek a permit to conduct sonar exercises during RIMPAC 06. This was granted by the US National Marine and Fisheries Service, though a subsequent court challenge by a US interest group resulted in a restraining order against the US Navy, citing `overwhelming evidence’ that active sonar can injure marine mammals. Subsequent negotiation saw the exercise proceed, but with significant mitigation measures in place.
Despite lack of scientific consensus, circumstantial evidence surrounding some whale strandings is enough to suggest the need to manage the potential adverse impact of some types of active sonar. Indeed, the Australian Environment Protection and Biodiversity Conservation Act 1999 prescribes such a precautionary approach in cases where complete data is not available. The EPBC Act also focuses on critical habitat for each species, most importantly feeding, breeding and resting areas. These obligations formed the basis for the RAN developing appropriate mitigation standards to avoid adverse impacts on marine mammals.
Managing the potential for impact is challenging in an environment where the animals are mostly unseen, elusive, and have poorly understood physiology and behaviour. Some of the principal mechanisms available include separation of activities from known whale congregations in space and time (a planning function), detection and avoidance methods using observers, and management of transmissions to reduce received sound intensities to accepted levels where interactions are considered likely.
In recent years the RAN sought to develop environmental management strategies that would be recognised as amongst the best in the world, employing all of these mitigation techniques. Of particular note was the decision to adopt a consultative approach, ensuring that key government agencies, interest groups and the public had an opportunity to participate in the development of appropriate management strategies.
Levels of Management
The Maritime Activities Environmental Management Plan (MAEMP) was progressively developed and finally implemented in 2005, to ensure that activities routinely conducted at sea are managed in a way that meets legislative obligations and community expectations, using a widely endorsed framework. The MAEMP has been designed with three levels of management:
- Planning Handbooks for some key training areas where a range of activities may be conducted simultaneously, to assist exercise planners in considering cumulative impacts and location specific issues.
- Planning Guides provide guidance on specific activities during the activity planning phase. Where necessary, both the Planning Handbooks and Guides recommend separation of an activity from a critical habitat.
- Procedure Cards provide specific guidance on individual activities, recognising the importance of managing activities in real time.
The MAEMP is widely acknowledged as amongst the most comprehensive and effective in use today, and has enhanced the RAN’s reputation for proactive and innovative management of marine environmental issues. The MAEMP has also been well accepted by RAN personnel, who are keen to ensure that their responsibilities for environmental compliance and sustainable management are met.