Comparing methods suitable for monitoring marine mammals in low visibility conditions during seismic surveys

Abstract

Loud sound emitted during offshore industrial activities can impact marine mammals. Regulations typically prescribe marine mammal monitoring before and/or during these activities to implement mitigation measures that minimise potential acoustic impacts. Using seismic surveys under low visibility conditions as a case study, we review which monitoring methods are suitable and compare their relative strengths and weaknesses. Passive acoustic monitoring has been implemented as either a complementary or alternative method to visual monitoring in low visibility conditions. Other methods such as RADAR, active sonar and thermal infrared have also been tested, but are rarely recommended by regulatory bodies. The efficiency of the monitoring method(s) will depend on the animal behaviour and environmental conditions, however, using a combination of complementary systems generally improves the overall detection performance. We recommend that the performance of monitoring systems, over a range of conditions, is explored in a modelling framework for a variety of species.

Scaling the Laws of Thermal Imaging–Based Whale Detection

“…Because whales would produce both weak and strong blows over time, the decrease in perceptibility of weak blows (though still .50%, Fig. 4a) at distances greater than 3 km, is not overly concerning in a mitigation context especially because mitigation and monitoring zones generally have radii ,3 km (Verfuss et al 2016). Perceptibility was shown not to be influenced by relative humidity (Fig.…”

“…It has previously been shown that fog has a significant impact on the transmission of longwave infrared (LWIR) radiation due to an increase in Mie scattering with large fog droplets (Verfuss et al 2018). Unfortunately, the impact fog has on the ability of the system to detect whales is impossible to measure within the thermal perceptibility protocol as human observers are also strongly impacted by fog.…”

“…PAM is only effective when marine mammals vocalize frequently, and when vocalizations are not masked by vessel or other background noise. With the goal of improving marine mammal detections beyond using these traditional methods, studies in recent years have evaluated the use of thermal imaging cameras to detect marine mammals at the ocean's surface (Verfuss et al 2018) and to make such detections automatically (Santhaseelan et al 2012;Zitterbart et al 2013). Thermal imaging systems have been used to detect marine mammals during nighttime hours for a few decades (Perryman et al 1999;Schoonmaker et al 2008), and an automatic detection system has been described and used in recent years (Zitterbart et al 2013;Smith et al 2020), but methods have not yet been standardized.…”

Critical information gaps remain in understanding impacts of industrial seismic surveys on marine vertebrates

“…Globally, and sometimes even within waters of the same country (e.g. the United States), no single minimum standard of mitigation measures exists (Verfuss et al 2018). In countries where mitigation measures are recommended, the standards are often guidelines rather than requirements (Compton et al 2007, Parsons et al 2009, Nowacek et al 2015.…”

Evaluating effects of dredging-induced underwater sound on aquatic species : a literature review

“…Dedicated marine mammal observers (MMO) or protected species observers (PSOs) can monitor zones prior to and during operations to provide real-time information (ACCOBAMS 2013; NOAA 2016). Additionally, passive acoustic monitoring systems can be used to detect the presence of vocally active species around exclusion zones, especially when visual observations by MMOs are impaired (i.e., during night and inclement weather, or due to submerged animals; Verfuss et al 2018). If organisms are observed inside exclusion zones, operations are halted until the organisms have vacated the zone (NOAA 2016).…”