Abstract
To investigate the potential impacts of naval mine neutralization exercises (MINEX) on odontocete cetaceans, a long-term passive acoustic monitoring study was conducted at a US Navy training range near Virginia Beach, USA. Bottom-moored acoustic recorders were deployed in 2012–2016 near the epicentre of MINEX training activity and were refurbished every 2–4 months. Recordings were analysed for the daily presence/absence of dolphins, and dolphin acoustic activity was quantified in detail for the hours and days before and after 31 MINEX training events. Dolphins occurred in the area year-round, but there was clear seasonal variability, with lower presence during winter months. Dolphins exhibited a behavioural response to underwater detonations. Dolphin acoustic activity near the training location was lower during the hours and days following detonations, suggesting that animals left the area and/or reduced their signalling. Concurrent acoustic monitoring farther away from the training area suggested that the radius of response was between 3 and 6 km. A generalized additive model indicated that the predictors that explained the greatest amount of deviance in the data were the day relative to the training event, the hour of the day and circumstances specific to each training event.
Highlights
The use of underwater explosives and other high-amplitude impulsive sound in industrial activities, hydrocarbon exploration and military training is becoming increasingly common in many marine habitats around the world, raising concerns about2017 The Authors
Marine mammals are vulnerable to these types of sounds because 2 of their dependence on hearing and acoustic signalling for sensing their environment, finding prey and communicating with conspecifics [1,2]
The objectives of this study were to: (i) determine the daily, monthly and seasonal occurrence of dolphins near the primary location of mine neutralization exercises (MINEX) training, (ii) quantify the acoustic activity of dolphins in response to MINEX training events, (iii) establish the distance from the training area at which a response is observable, and (iv) identify the predictive factors associated with dolphin acoustic response to training events
Summary
The use of underwater explosives and other high-amplitude impulsive sound in industrial activities, hydrocarbon exploration and military training is becoming increasingly common in many marine habitats around the world, raising concerns about2017 The Authors. The naval forces of many nations conduct mine neutralization exercises in coastal waters as part of their regular training These exercises typically involve detonating explosives in areas often co-habited by various species of marine mammals and, have the potential to disturb, injure or kill animals occurring there. In March 2011 three common dolphins (Delphinus delphis) were killed at the US Navy’s Silver Strand Training Complex off San Diego, California during a training exercise using underwater explosives [11]. In this particular case, the animals entered the training area after initiation of a timedelayed detonation that could not be safely aborted. One of the principal monitoring goals is to increase understanding of how marine mammals respond to sonar, UNDETs or other stimuli that result in the anticipated ‘take’ of individual animals, defined as hunting, harassing, capturing or killing a marine mammal [12]
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