Oceans of noise - Whale and Dolphin Conservation Society

identification of images collected. This method is useful where populations are expected to be
found in, or return to, an area repeatedly and where individuals have distinctive marks.
Data loggers and telemetry
Tagging devices record information for either later retrieval, or for continuous remote monitoring
of cetacean movements. It is possible to acquire detailed data on many aspects of wildlife
biology using increasingly sophisticated tags, for example, dive depths, durations, water
temperature, and time spent at the surface as well as levels of biological and anthropogenic noise.
Data may be collected for periods of hours, weeks or months.
However, this may also be an expensive and time-consuming technique, and such devices have
proved to be unsuitable for use in some species (for example due to the animal’s size) although
this is changing as technology advances and costs decrease. Physiological impacts (of the tag in
addition to the noise itself, as well as impacts associated with close contact with the animal for
attachment) have not been investigated to any great extent, and there are other limitations, such as
battery life. Consideration should also be given to the invasiveness of this process. It is important
to consider the value of the information gained against the disturbance and damage that may be
inflicted upon the individual.
Image intensifiers and infra-red sensors
Such devices are used in some areas of the world to monitor for cetaceans at night. Whilst all
attempts to monitor cetaceans exposed to loud noise are welcomed, we have concerns about the
abilities of such devices to detect cetaceans, both at night and in poor weather conditions.
Active and passive acoustic methods
Vessel-mounted acoustic detection systems have been proposed as a solution to collisions for
some depleted species. Such devices may warn the vessel that a cetacean is in the area, or warn
the animal, and hopefully encourage it to move away from the source of the noise, and hence the
vessel. Gerstein (2002) developed a highly directional low intensity acoustic alerting device to
alert manatees to vessels to prevent collisions.
The US Navy has invested in the HF/M3 detection system for its Low Frequency Active Sonar
(LFAS) program. An active acoustic deterrent is an alarm signal to warn the cetacean to move
away. As part of the Sound Oceanography and Living Marine Resources (SOLMAR) project, the
NATO SACLANT Undersea Research Centre is investigating the use of active sonar for the
detection and localisation of marine mammals as an early warning, collision-avoidance sonar for
shipping (Bondaryk 2001). The consequences of addition noise in the marine environment should
be weighed up against the effectiveness of the system. There are also issues with habituation (see
chapter 5). Passive acoustics are often used as a mitigation measure for noise sources, in an
attempt to localise cetaceans by their own sounds and ensure that there are no cetaceans nearby.
Unfortunately, the reactions of many cetaceans may be to fall quiet when they hear noise, which
can be expected to reduce the effectiveness of this mitigation method.
Andre and Potter’s (2001) preliminary findings indicate that the solution to the problem of
accidental collisions may lie in a better understanding of the hearing sensitivities of the local
populations of whales, coupled with measures to decrease acoustic exposures of these whales
rather than by increasing the acoustic loading by deployment of active acoustic deterrents.
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