The ET&BF is presently dealing separately with a number of ecological issues. For example, impacts of longliners on shearwaters and turtles are current high profile problems. However, other issues such as depletion of swordfish, SBT bycatch, availability of tunas in relation to oceanographic features, bycatch of sharks and finning have all taken centre stage at different times in the short history of the domestic fishery. This approach is often reactionary, rather than strategic, and may not be the best use of research resources over the long-term. If the ET&BF is to move substantially toward ecosystem-based fishery management, as it is required to do under the EPBC act, rather than continue the individual species management approach, an ecosystem analysis providing ecosystem metrics must be developed. If, for example, ET&BF managers opt for time area closures as part of their management strategy to protect key species, developing these on a species-by-species basis has the potential to impact the whole fishery. To develop and evaluate time area closures that allow for minimizing risk of adverse impacts to the suite of key species, while allowing for optimal efficiency of fishing, understanding the associations, linkages and interactions between species is essential. This is the ecosystem approach. Developing an understanding of how ecosystem-associations relate to oceanographic features is also essential in open ocean systems where the dominant influence on distribution and local abundance is oceanography. The approach we are taking will provide the information needed to support an ecosystem-based management framework. Through the analyses we are proposing we will identify regional “hot spots”, detail their linkages and provide detailed scenarios as to how we think different management strategies and fishing practices will or will not impact pelagic food chains, ecologically related non-target species, competitors (e.g. sharks, marlins etc.) and their associated ecosystems. The need for ecosystem-based fishery management for the Western Pacific region has also been supported by PrepCon for the soon-to-be formed WCPFC (Working Paper 9, 2002).

Recent studies into the effects of seismic energy on molluscs have demonstrated a number of cumulative and sub-lethal impacts that indicated impairment of immune systems, cellular damage and adverse changes in behaviour. In scallops, cumulative exposure to seismic energy resulted in increased rates of mortality after 120 days (R Day et al. (2017)). These findings are of critical importance to the pearling industry, which relies on the harvest and husbandry of pearl oysters in coastal shelf water . Pearl oyster crops are typically 2 years duration, so long term effects will have a chronic sub-lethal effect on pearl production. In addition, as the oysters were still not fully recovered at the day 180 sampling, there is concern that the long recovery time may result in a reduction of the reproductive output for up to one year. Energetically compromised oysters will have a reduced reproductive output, and a higher proportion of male oysters, as egg production is more energy intensive.

This would have major ramifications for recruitment into the wildstock pearl oyster fishery and the pearling industry it underpins.

To these ends it became apparent that a 4th sampling round was critical in order to provide a condition data from the oyster sample set after 360 days; so that the responses of the oysters to seismic treatment may be better understood after the completion of one year – bearing in mind that at different times of the year oysters do different things.

The overarching objective of this experiment is to measure the impact of seismic surveys on wild harvested pearl oysters in a way that provides information that is useful to stakeholders in the pearl production and oil and gas industries and to the managers of these resources. The uncertainty surrounding the long-term impacts of seismic surveys on the health of pearl oysters and their pearl production capacity is the key driver of this study.