contact [EMAIL PROTECTED] for a copy:
Kastelein, R., W. Verboom, M. Muijsers, N. Jennings, and S. van der Heul.
2005.
The influence of acoustic emissions for underwater data transmission on the
behaviour of harbour porpoises (Phocoena phocoena) in a floating pen. Marine
Environmental Research 59:287-307.
Abstract:
To prevent grounding of ships and collisions between ships in shallow
coastal waters, an underwater data collection and communication
network is currently under development: Acoustic Communication network
for Monitoring of underwater Environment in coastal areas
(ACME). Marine mammals might be affected by ACME sounds since they use
sounds of similar frequencies (around 12 kHz) for communication,
orientation, and prey location. If marine mammals tend to avoid the
vicinity of the transmitters, they may be kept away from ecologically
important areas by ACME sounds. One marine mammal species that may be
affected in the North Sea is the harbour porpoise. Therefore, as part
of an environmental impact assessment program, two captive harbour
porpoises were subjected to four sounds, three of which may be used in
the underwater acoustic data communication network. The effect of each
sound was judged by comparing the animals' positions and respiration
rates during a test period with those during a baseline period. Each
of the four sounds could be made a deterrent by increasing the
amplitude of the sound. The porpoises reacted by swimming away from
the sounds and by slightly, but significantly, increasing their
respiration rate. From the sound pressure level distribution in the
pen, and the distribution of the animals during test sessions,
discomfort sound level thresholds were determined for each sound. In
combination with information on sound propagation in the areas where
the communication system may be deployed, the extent of the
'discomfort zone' can be estimated for several source levels
(SLs). The discomfort zone is defined as the area around a sound
source that harbour porpoises are expected to avoid. Based on these
results, SLs can be selected that have an acceptable effect on harbour
porpoises in particular areas. The discomfort zone of a communication
sound depends on the selected sound, the selected SL, and the
propagation characteristics of the area in which the sound system is
operational. In shallow, winding coastal water courses, with
sandbanks, etc., the type of habitat in which the ACME sounds will be
produced, propagation loss cannot be accurately estimated by using a
simple propagation model, but should be measured on site. The SL of
the communication system should be adapted to each area (taking into
account bounding conditions created by narrow channels, sound
propagation variability due to environmental factors, and the
importance of an area to the affected species). The discomfort zone
should not prevent harbour porpoises from spending sufficient time in
ecologically important areas (for instance feeding areas), or routes
towards these areas.
|