A western gray whale mitigation and monitoring program for a 3-D seismic survey, Sakhalin Island, Russia

Abstract

The introduction of anthropogenic sounds into the marine environment can impact some marine mammals. Impacts can be greatly reduced if appropriate mitigation measures and monitoring are implemented. This paper concerns such measures undertaken by Exxon Neftegas Limited, as operator of the Sakhalin-1 Consortium, during the Odoptu 3-D seismic survey conducted during 17 August’ September 2001. The key environmental issue was protection of the critically endangered western gray whale ( Eschrichtius robustus ), which feeds in summer and fall primarily in the Piltun feeding area off northeast Sakhalin Island. Existing mitigation and monitoring practices for seismic surveys in other jurisdictions were evaluated to identify best practices for reducing impacts on feeding activity by western gray whales. Two buffer zones were established to protect whales from physical injury or undue disturbance during feeding. A 1 km buffer protected all whales from exposure to levels of sound energy potentially capable of producing physical injury. A 4’ km buffer was established to avoid displacing western gray whales from feeding areas. Trained Marine Mammal Observers (MMOs) on the seismic ship Nordic Explorer had the authority to shut down the air guns if whales were sighted within these buffers. Additional mitigation measures were also incorporated: Temporal mitigation was provided by rescheduling the program from June–August to August–September to avoid interference with spring arrival of migrating gray whales. The survey area was reduced by 19% to avoid certain waters <20 m deep where feeding whales concentrated and where seismic acquisition was a lower priority. The number of air guns and total volume of the air guns were reduced by about half (from 28 to 14 air guns and from 3,390 in 3 to 1,640 in 3 ) relative to initial plans. ‘Ramp-up’(=‘soft-start’ procedures were implemented. Monitoring activities were conducted as needed to implement some mitigation measures, and to assess residual impacts. Aerial and vessel-based surveys determined the distribution of whales before, during and after the seismic survey. Daily aerial reconnaissance helped verify whale-free areas and select the sequence of seismic lines to be surveyed. A scout vessel with MMOs aboard was positioned 4 km shoreward of the active seismic vessel to provide better visual coverage of the 4’ km buffer and to help define the inshore edge of the 4’ km buffer. A second scout vessel remained near the seismic vessel. Shore-based observers determined whale numbers, distribution, and behavior during and after the seismic survey. Acoustic monitoring documented received sound levels near and in the main whale feeding area. Statistical analyses of aerial survey data indicated that about 5’0 gray whales moved away from waters near (inshore of) the seismic survey during seismic operations. They shifted into the core gray whale feeding area farther so...

Behavioural responses of western gray whales to a 4-D seismic survey off northeastern Sakhalin Island, Russia

“…To minimize the impacts of such activity on the whales, several mitigation and monitoring plans (MMP) have been implemented targeting specific activities, such as seismic surveys, platform installation, dredging and pipeline placement (Johnson et al 2007, SEIC 2005, 2006. Despite efforts to reduce overall sound exposure levels, responses by the whales were observed, including changes in distribution and behaviour (Weller et al 2002,b, 2010, Yazvenko 2007a.…”

Nowhere to go: noise impact assessments for marine mammal populations with high site fidelity

“…During the summer of 2001, 3D seismic surveys were conducted from 17 August to 9 September in prime gray whale foraging habitat (Odoptu) off Sakhalin Island (Johnson et al 2007). Systematic observations of whales in relation to operational condition (i.e.…”

“…Systematic observations of whales in relation to operational condition (i.e. pre-seismic, seismic, post-seismic) showed that a significantly lower number of individuals and groups were seen during seismic surveys, compared to pre-and post-seismic conditions (Weller et al 2006, Johnson et al 2007). This indicates a potential for harm caused by displacement of this endangered subpopulation from foraging areas (Weller et al 2006).…”

Responsible Practices for Minimizing and Monitoring Environmental Impacts of Marine Seismic Surveys with an Emphasis on Marine Mammals

“…For example, the Exxon-Neftegas Limited (ENL) development in eastern Russia (Sakhalin-I) uses assets on shore to drill wells to reach and extract oil and gas from deposits 5 to 10 km offshore. It was nonetheless impossible for ENL to avoid its 2001 Odoptu 3-D seismic survey in support of the Sakhalin-I development (Johnson et al, 2007), and further 4-D seismic surveys of the Odoptu field will inevitably be required as the development proceeds.…”