PASSIVE ACOUSTIC MONITORING OF MARINE MAMMALS

A Passive Acoustic Monitoring (PAM) cable attached to a streamer on a seismic survey vessel in New Zealand. © OSC 2013.

A Passive Acoustic Monitoring (PAM) cable attached to a streamer on a seismic survey vessel in New Zealand. © OSC 2013.

Marine scientists use Passive Acoustic Monitoring (PAM, www.pamsystem.co.uk) as a research technique for listening to vocalisations emitted by marine mammals. In addition to research, PAM is used regularly for mitigation purposes in offshore industries, such as seismic surveys (www.marinemammalseismic.co.uk), construction (bridges, wind farm piling, etc.), oil and gas rig/platform decommissioning, underwater explosives, and military exercises. Environmental guidelines regarding marine mammals vary depending on the country of work (www.marinemammalmitigation.co.uk), and in some regions, the use of PAM is mandatory.

NEW ZEALAND SEISMIC SURVEY GUIDELINES

In New Zealand, the Department Of Conservation (DOC), alongside a range of domestic and international stakeholders, has produced the ‘Code of Conduct for Minimising Acoustic Disturbance to Marine Mammals from Seismic Survey Operations’, known simply as ‘the Code’ (http://www.doc.govt.nz). For more information on these guidelines and the qualifications required to work as a PAM Operator in New Zealand, please refer to www.codeofconductseismicnewzealand.com

NEW ZEALAND PAM OPERATOR DUTIES

The Code has strict and easily discernible guidelines regarding PAM Operator requirements and duties. The Code specifies the requirement of two PAM Operators aboard the vessel at all times for Level 1 surveys and for Level 2 surveys also, if PAM is installed (see www.codeofconductseismicnewzealand.com for details on seismic survey levels). One PAM Operator must be on watch when the acoustic source (e.g. seismic airguns) is in the water in the operational area. If the acoustic source remains in the water, but is inactive for extend periods of time (e.g. during periods of bad weather), it is acceptable for the PAM Operator to ‘stand down’ to attend to other duties relating to PAM Operator roles (e.g. adjusting equipment, report writing, etc.). Observational duties must be resumed at an appropriate time before operations recommence. If there is a Marine Mammal Observer (MMO, www.marinemammalobserver.com) aboard, with adequate understanding of PAM, they may be able to provide temporary cover for the PAM Operator to ensure a continuous watch is maintained. These short breaks are usually for meals, toilet or refreshment breaks, and the PAM Operator remains responsible for the watch and PAM equipment.

Dolphin detection off the Taranaki coast, New Zealand. Shown in the software programme PAMGuard. © OSC 2013.

Dolphin detection off the Taranaki coast, New Zealand. Shown in the software programme PAMGuard. © OSC 2013.

It is extremely important that the PAM Operator, and MMO during daylight hours, carries out a 30 minute pre-watch immediately preceding source activation, as the source cannot be activated unless it is known that no marine mammals were observed in the mitigation zones. Initial acoustic source activation at a new location in the survey programme necessitates extra requirements during hours of darkness or poor visibility. For example, in addition to MMO requirements, the PAM Operator must undertake two hours of monitoring immediately before activation with no marine mammals observed in the respective mitigation zones.

If the PAM system becomes damaged at any point during operations, the PAM Operator has 20 minutes to diagnose the problem whilst operations continue. If the PAM equipment needs to be repaired, operations may continue for a further two hours without PAM, but this is only possible during daylight hours.

For a full list of PAM Operator duties, please see the Code (http://www.doc.govt.nz).

DELAY & SHUT DOWN

The Code gives authority to either PAM Operators or MMOs to delay the start of operations, or shut down an active source, independently of each other. When either observer detects a marine mammal, dialogue should be initiated between the MMO (www.marinemammalobservers.co.uk) and PAM Operator (www.passiveacousticmonitoring.co.uk) to ensure the correct outcome is achieved. When operating in an area where calves have been observed or are expected to be present, all cetacean vocalisations detected by PAM should be assumed to be originating from a cow/calf pair because this enforces the most stringent mitigation zone, unless the MMO is able to determine otherwise. Any ultra-high frequency cetacean detections require immediate shut down of the active survey (unless an MMO confirms it is a species classified as ‘other marine mammals’), or a delay in start of operations, because high frequency sound does not propagate long distances, resulting in a shorter detection range of certain species.

RECORDING AND REPORTING

For more information about the recording and reporting procedure, please refer to www.marinemammalmitigation.org

Streamers from a seismic survey vessel in New Zealand. © OSC 2013.

Streamers from a seismic survey vessel in New Zealand. © OSC 2013.

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