Potential impacts of marine seismic surveys on fish & invertebrates

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.

海洋地震勘探产生的低频声波对海洋动物的影响程度正日益受到关注。地震气枪发射的主要频率范围处于鲸类、爬行动物与鱼类的听觉区间内，还可对部分无脊椎动物引发神经反应。长期以来，近海地震勘探被认为会干扰渔业生产，但针对具有商业价值的物种在真实暴露场景下的研究相对匮乏。水下声波影响研究的核心挑战之一，是如何将实验室结果合理外推至野外环境。水下声波特性受声源、水柱属性、底质条件以及生物群落特征的共同制约。实验设置对精准的响应测量同样至关重要，饲养水槽的设计缺陷可能导致结果解读出现偏差，尤其是在行为相关研究中。人们往往倾向于简化实验室结果，将其简单判定为存在影响或无影响，但实际应结合真实暴露场景与野外条件进行严谨解读。

本项目旨在回应渔业行业利益相关方对吉普斯兰盆地4月地震勘探的担忧，同时也为获取基线数据以量化地震作业对海洋生物的潜在影响提供支撑。本研究包含六个部分：1）声波建模，2）利用系泊水听器开展声波监测，3）借助自主水下航行器（Autonomous Underwater Vehicle，AUV）进行底栖生物群落评估，4）通过拖网采样开展双壳类生物评估，5）采用声学标记法研究鱼类的规避行为，6）分析与地震勘探相关的渔业捕捞数据。在本次报告中，我们将对上述研究内容进行介绍，并批判性回顾当前学界对低频声波影响海洋鱼类与无脊椎动物的认知现状。