Appendices 5-13 - Nautilus Cares - Nautilus Minerals

conditions (noting that for a signal to be discernible amongst the background noise it
needs to be a few dB above the ambient conditions). It would not be inconceivable that
some whales are attracted to the vessel noise out of "curiosity" or that through time the
vessel becomes considered by resident animals as “landmarks”.
Avoidance and behavioural effects
The estimated noise levels calculated indicate that when the mining vessel is working an
approaching marine animal may detect the facility at hundreds of km. If the wind picks up
then the range where the vessel is clearly audible will drop. Although the vessel may be
audible at potentially long ranges its noise will not be greatly above background noise
conditions. As the animal approaches the vessel the underwater noise will become more
intense and perceived by an animal as louder. But, it would not be until the animal is
within perhaps 1-2 km of the vessel that the signal could be considered to be ‘loud’, as
indicated by the 140 dB re 1"Pa level.
Richardson et. al. (1995) have summarised many workers findings on the response of
great whales to noise. Several features emerge from this summary:
* there is definitive evidence of behavioural responses of great whales to various
noise sources;
* the type of response is variable, and ranges from none to active avoidance of a
source;
* there is evidence that at the species level whales respond differently to a given
noise depending on their gender, behavioural state and habits at that particular
time;
* there is evidence that the response of a species to man-made noise may change
through time due to familiarisation or sensitisation of whales to the noise source.
Richardson et. al. (1995) summarises several workers observations to, and experimental
playbacks of, petroleum drilling and associated industrial noise to mostly gray and
bowhead whales. Their summary states "that stationary industrial activities producing
continuous noise result in less dramatic reactions by cetaceans than do moving sound
sources, particularly ships". They noted that some cetaceans approached industrial noise
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