Automatic Round-the-Clock Detection of Whales for Mitigation from Underwater Noise Impacts

Abstract

Loud hydroacoustic sources, such as naval mid-frequency sonars or airguns for marine geophysical prospecting, have been increasingly criticized for their possible negative effects on marine mammals and were implicated in several whale stranding events. Competent authorities now regularly request the implementation of mitigation measures, including the shut-down of acoustic sources when marine mammals are sighted within a predefined exclusion zone. Commonly, ship-based marine mammal observers (MMOs) are employed to visually monitor this zone. This approach is personnel-intensive and not applicable during night time, even though most hydroacoustic activities run day and night. This study describes and evaluates an automatic, ship-based, thermographic whale detection system that continuously scans the ship’s environs for whale blows. Its performance is independent of daylight and exhibits an almost uniform, omnidirectional detection probability within a radius of 5 km. It outperforms alerted observers in terms of number of detected blows and ship-whale encounters. Our results demonstrate that thermal imaging can be used for reliable and continuous marine mammal protection.

Distance Sampling: Methods and Applications

“…Therefore, automated detection and classification of animals from images (e.g. Zitterbart et al 2013;Yang et al 2014) and acoustic data (e.g. Gillespie et al 2013) is becoming an important research area.…”

“…Infrared cameras have been used in combination with aerial surveys of deer (Storm et al 2011). Infrared video cameras can also be used to complement visual sightings for boat surveys (Zitterbart et al 2013) and will probably see more use in coming years as the cost of such technology drops.…”

Thermal Imaging and Biometrical Thermography of Humpback Whales

“…Although blows imaged at <200 m range were easily recognizable with the A615 (Figures 4A,B,D), a blow imaged at ∼400 m range appeared as an 8 pixel tall ∼0.4 • C BTA ( Figure 4E). Higher sensitivity cooled detector thermal imaging devices and/or devices with longer focal lengths would no doubt extend the range at which whale blows might be detectable (e.g., Zitterbart et al, 2013). However, these larger systems are FIGURE 3 | Thermographic profiles of emergent humpback whale blows and body parts in both tropical (Rarotonga, Cook Islands) and sub-polar (Sitka Sound, Alaska, U.S.A.) waters.…”

“…Quantitative constraints on the magnitude, size and duration of whale-derived thermal anomalies can also be used to help restrict the number of false positives and false negatives produced by automated cetacean detection systems that use transient thermal contrast algorithms based on average brightness temperatures (e.g., Zitterbart et al, 2013). Improving automated detection systems in this way should assist applications in windy conditions or large swells, when ocean surface roughness has the potential to produce thermal anomalies of similar magnitude as whale blows due to emissivity effects (e.g., Figure 4E).…”

“…Acoustic and infrared automated cetacean detection systems are attractive and emerging tools for enhanced cetacean conservation (Zitterbart et al, 2013;Nowacek et al, 2016). The ability to detect whale blows, as far away as 5 km using around-the-clock 360 • infrared scanners outfitted with rigorous detection algorithms (Zitterbart et al, 2013), will benefit many, including marine mammal observers onboard large vessels and land-based scientists studying whale movement behavior (e.g., Perryman et al, 1999) and human-whale interactions along rapidly changing coastlines (e.g., Graber, 2011). Infrared thermography can also facilitate the non-invasive collection and monitoring of fundamental biometrical information, including thermal physiology, injury diagnoses and population surveys (McCafferty, 2007).…”