The extent to which low-frequency sound from marine seismic surveys impacts marine fauna is a subject of growing concern. The predominant frequency range of seismic airgun emissions is within the hearing range of cetaceans, reptiles, and fishes, and it can also elicit a neurological response in some invertebrates. Offshore seismic surveys have long been considered to be disruptive to fisheries, but comparatively few studies target commercially important species in realistic exposure scenarios. One of the main challenges in underwater sound impact studies is the meaningful translation of laboratory results to the field. Underwater sound properties are affected by the sound source, as well as characteristics of the water column, substrate, and biological communities. The experimental set-up is also critical to accurate response measurement, and design features of holding tanks can lead to misinterpretation of results, particularly related to behaviour. It may be tempting to simplify laboratory results to show effect or no effect, where results should instead be interpreted in the context of realistic exposure scenarios and field conditions.
The current project was developed in response to stakeholder concerns from the fisheries industry about an April seismic survey in the Gippsland Basin, in addition to a broader need to acquire baseline data that may be used to quantify potential impacts of seismic operations on marine organisms. The study involves six components: 1) sound modelling, 2) sound monitoring using moored hydrophones, 3) benthic community assessment using an AUV, 4) bivalve assessment using dredging 5) fish avoidance behaviour using acoustic tagging, and 6) analysis of fisheries catch data as related to seismic surveys. In this presentation, we describe these components and critically review our current understanding of low-frequency sound impact on marine fish and invertebrates.
