In 2016, the Responsible Fisheries Alliance contracted Namibian fisheries consultant, William David Russell, to conduct a desktop study to assess the impact of seismic surveys on South African fisheries. This study was concluded in April 2018 and it is hoped that the findings of the report, will act as a resource for strategic discussions going forward with the seismic exploration industry, government, and the fishing industry, to help mitigate against the impacts of seismic surveys.
Marine seismic surveys are the most important tool the authorities and the petroleum industry have for mapping potential deposits of oil and gas under the seabed. During these surveys, air guns are discharged about every 10-15 seconds and sound pulses with a short rise time and very high peak sound pressure level are emitted. Concerns have been raised about the impacts of seismic air gun emissions on marine life with a wide variety of studies showing that cetaceans, fish, squid, and turtles respond to seismic airgun sounds. Fishermen in particular claim that seismic surveys have a serious negative influence on fish distribution and commercial catch rates.
In the South African fisheries section of the report, Dave Russell’s findings reveal that seismic surveys appear not to impact hake in the long term, only causing temporary behavioural disruption. The West coast tuna pole and line fishery showed localised impacts, disrupting fast swimming tunas migration flow by forcing them to move on. Where there are cumulative impacts from repetitive surveys in the same area, there is the possibility that tuna change their migration path. This has occurred off Southern Namibia tuna fishing grounds, where catches have severely declined since 2011, and in 2017 dropped off to non-commercial catch rates. Seismic surveys appear not to noticeably impact horse mackerel. Squid, however, experience an impact of low frequency seismic sound which is of serious concern since there appears to be a drop in squid jig catches with seismic surveys. Whilst rock lobster has experienced no significant drop in catches, research is required on different life history stages, which have different levels of sensitivity to airgun sounds. Findings among related species show that egg development among specific crustaceans may be retarded, metabolic rates increased and internal organs damaged following exposure to high amplitude anthropogenic sound. Similar impacts are thought to exist for the prawn trawl fishery.
The report suggests working towards implementing worldwide best practice mitigation procedures. Seismic surveys should be co-operatively designed around fishing areas and seasons to limit disruption, and intensive seismic periods limited on South African south and west coast. Lastly, Dave Russell suggests that the fishing industry should work cooperatively with government regulatory bodies, and seismic exploration mining companies to ensure responsible mitigation measures are put in place. This will consequently address concerns in priority fisheries and reduce or eliminate impacts on marine life.
DAFF has put together a task team to discuss opportunities for local experimental research to better understand the impacts of seismic survey activity. This report has been shared with the task team and the RFA will continue to keep a watching brief on developing research in this space.
The RFA report on the impact of seismic surveys can be found as an attachment below: