Marine Seismic Survey – Habitat Impact Assessment Outcomes
In early 2018 the CarbonNet Project undertook a 3D marine seismic survey (MSS) in the offshore Gippsland Basin in Bass Strait. The survey was carried out by the vessel Polarcus Naila between the 10th and 24th of February 2018. The environmental impacts and risks associated with the MSS were comprehensively described in the Environment Plan (EP) which was accepted by Commonwealth and Victorian regulators.
Underwater sound and its impact on the marine environment was a key issue raised by stakeholders, particularly commercial fishermen. In response, CarbonNet put in place initiatives to address concerns, including:
- undertaking marine habitat assessments before and after the MSS
- establishing an independent Advisory Panel of fisheries experts to provide advice on the marine habitat assessments
- monitoring underwater sound levels to confirm levels were consistent with predictions, and
- contributing to a scallop stock assessment by the Victorian Fisheries Authority.
“Overall, no impact was observed that could be attributed to the MSS. Scallop numbers were extremely low both before and after the MSS. Rock lobster numbers increased post the MSS. Results from fish and zooplankton were highly variable with both pre– and post–MSS samples considered typical of a healthy temperate marine ecosystem”. – Advisian
Summary of the initiatives
Marine habitat assessments
The objectives of the habitat assessments were to confirm the abundance of key marine species before and after the MSS, and to determine whether any differences could be attributed to the MSS. The pre- and post-MSS habitat assessments focused on:
- commercial scallops (Pecten fumatus)
- southern rock lobster (Jasus edwardsii)
- finfish, and
Pre-MSS habitat assessments were carried out between 15 to 26 January 2018.
Following completion of the MSS on the 24 February 2018, and based on advice from the Advisory Panel, post-MSS habitat assessments were conducted on 26 February for zooplankton, 10 to 12 July for finfish and rock lobster, and 22 and 23 August for scallops.
Selection of monitoring sites for the habitat assessments
Monitoring sites were selected within the MSS area and at reference locations surrounding it. A total of 68 sites were monitored during the assessments.
Reference site habitats were similar to those in the survey area, but were distant enough to be unaffected by sound from the MSS.
Specialist modelling was carried out prior to the survey to predict the sound levels which was then verified by underwater monitoring equipment. The sound levels measured were lower than predicted.
Independent advisory panel
To ensure that the marine habitat assessments were undertaken in a scientifically robust manner, an independent advisory panel was established consisting of representatives from government agencies, academia and the fishing industry. Its role was to provide advice on:
- the methodology to undertake the pre- and post-MSS habitat assessments
- information about the relevant fisheries
- the results from the pre- and post-MSS habitat assessments, and
- the interpretation of the assessment results and their implications.
The advisory panel met eight times between December 2017 and November 2018 to discuss, review and make recommendations on the planning and the results of the habitat assessments.
Offshore Habitat Assessments Final Report
The CarbonNet Pelican 3D Marine Seismic Survey (MSS) Offshore Habitat Assessments Final Report found that, overall, no impact was observed in the marine habitat that could be attributed to the MSS. The report was accepted by the Advisory Panel.
The pre- and post-MSS marine habitat assessments provide an important contribution to the existing knowledge about the effects of seismic surveys on marine environments.
Victorian Fisheries Authority – Scallop Stock Assessment Survey
The Victorian Fisheries Authority undertook an ocean scallop abundance survey during December 2017 and January 2018. One hundred and seventy-six (176) tows were conducted during the assessment. Of these, 18 were conducted within the CarbonNet MSS operational area, validating CarbonNet’s assessments.
Page last updated: 30 Sep 2020