NO 7 2021 
ımplanting an acoustIic tag ı U EuUroDeAN Silver er 
masking, as well as hearing characteristics and strategies to reduce 
masking effects. The models to understand the range and exact 
ohysical impact of masking have also improved (see Erbe et al., 2016). 
Compared to mammals, there is less information on masking in 
fishes (Popper & Hawkins, 2019). One problem with understanding 
masking with respect to communication is that, in most cases, we do 
not know over which ranges marine mammals or fishes effectively 
communicate with each other. We can thus only speculate about the 
severity of the loss of communication space due to noise. 
One increasingly documented behavioural effect of masking, shown 
in both marine mammals and fishes, is the ‘Lombard effect’, when 
animals raise the amplitude and/or pitch of signals as a response 
to masking noise (see reviews by Erbe et al., 2016; Hawkins et al., 
2016). The concern here is mainly in relation to the energetic costs 
of compensating for the noise. 
Studies have shown that noise affects the soundscape surrounding 
an individual which can impair navigation, e.g. in fish and coral 
larvae (Simpson et al., 2005; Lecchini et al., 2018). Furthermore, 
increased background noise may prevent marine animals from 
detecting sounds produced by predators and prey, impacting their 
escape response and foraging behaviour (Ferrari et al., 2018). 
Behavioural response 
Behavioural response to noise has been widely studied mostly in 
marine mammals and less in fishes and even. to a lesser extent 
in invertebrates. Since EMB Position Paper N° 13, huge progress 
has been made in designing and conducting Controlled Exposure 
Experiments (CEE) in very large field efforts, which are required to 
collect these data. Such studies were really only beginning in 2008. In 
particular, there have been advances in passive acoustic monitoring 
(PAM) and especially automatically detecting and recording the 
behaviour of marine mammals and fishes underwater, and also in 
measuring the received sound levels on the animal (see Chapter 4 
new technologies). 
Acoustic tagging has allowed the expansion from studies mostly 
zarried out in a lab setting to those carried out in the field (e.g. 
r'homsen et al., 2012; Miller et al., 2014; Southall et al., 2014; Sivle 
ot al., 2015; Russell et al., 2016; Harris et al., 2018). In both marine 
mammals and fish, documented behavioural responses include 
startle reactions, the aforementioned Lombard effect, and short- 
and long-term avoidance of ensonified areas (i.e. areas where 
the sound is present). These effect ranges can have various sizes, 
ranging from small zones to many hundreds of square kilometres 
in some cases concerning mammals. In addition, marine mammals 
have been observed to change surfacing patterns and diving 
behaviour. Fishes reacted with ‘herding’ (school tightening). There 
is little information on response to noise in marine invertebrates, 
but a recent meta-analysis concluded that at least shipping noise 
can affect their behaviour (Murchy et al., 2020). It is worth pointing 
out that some studies also found no observable reactions of marine 
animals to anthropogenic noise at all (see reviews by Slabbekoorn et 
al., 2010: Hawkins et al., 2016: Erbe et al., 2018).