Seismic guidelines - protecting marine mammals

Dolphins, whales and seals at risk of injury and disturbance from seismic surveys have been protected by JNCC guidelines that have been widely adopted by UK’s offshore oil and gas industry over the last 16 years.

Offshore oil rig © Alex Brown

 

Licences for these industries require that the JNCC guidelines are considered as they are seen as a best practice model and used as a benchmark in other parts of the world. Orginally published in 1995, they have undergone several revisions through consultations with regulators and stakeholders, with a revised version due for publication later this year.

 

Seismic surveys are commonly used in the search for, and management of, oil and gas reserves. Towed arrays of 'airguns', cylinders of compressed air, are discharged at regular intervals to generate a pressure pulse which travels downwards into the seabed. The pulses’ reflections are then interpreted and plotted to reveal seabed composition. The pressure pulse results in a loud sound that travels mainly downwards but also radiates horizontally. Although no direct evidence links the use of airguns and animal injury (due in part to the challenges of collecting such evidence), data on hearing sensitivities of marine mammals and comparisons with terrestrial mammal data suggest that hearing could be damaged. There is also a risk that the animals may temporarily change their behaviour in response to the sound – for example stop vocalising or move away from the area.

 

Short Beaked Common Dolphin © P.Anderwaid_Seawatch Foundation

The JNCC guidelines recommend that trained observers are placed on seismic vessels as a precaution to prevent this hearing damage. Recommended procedures include a visual check for marine mammals to be made before the first airgun is fired, a delay in the start of the survey if a marine mammal is sighted within a 500m zone and a gradual build-up of the airguns’ power. In areas that are particularly sensitive and during the winter where visual observations are restricted, the guidelines also advise the use of underwater microphones to detect the sounds that marine mammals make. The use of this form of monitoring has increased in the last few years and has become more efficient at detecting animals nearby.

 

The information that those wishing to carry out seismic surveys have to supply is used to assess the risk of injury and disturbance to European Protected Species such as whales and dolphins and will also feed into the implementation of part of the EU’s Marine Strategy Framework Directive. After each seismic survey a report is submitted to JNCC detailing how the guidelines were implemented, the marine mammals sighted, and any problems encountered.

 

A report on the Effects of seismic activity on marine mammals in UK waters, 1998-2000 has been published and another one is planned for next year, summarising  observations from seismic survey vessels, assessing compliance with, and the success of, the JNCC guidelines since 2000.

 

 

Contact File

 

Sonia Mendes

Senior Offshore Advice Co-ordinator

Tel: +44 (0)1224 266558

 

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