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Guidance Note to recipients of:
Cooperative Research Report No. 209
(Underwater Noise of Research Vessels: Review and Recommendations)
ICES Cooperative Research Report No.
209 explains the need for noise reduction in research vessels
undertaking fishery resource surveys and makes practical recommendation
for limiting underwater radiated noise, to assist those drawing
up specifications for new vessels.
The basic concept is that research vessels surveying fish stocks
should not disturb the natural distribution of the target fish at
any operational speed. To maximise the area surveyed during a cruise,
research vessels normally sail at their maximum practical operating
speed. This is generally around 11 knots for acoustic surveys and
the report presents data for this speed. Survey speed is sometimes
limited by bad weather and trawl sampling is carried out at lower
speeds. It is thus obvious, but nevertheless worth noting, that
at all speeds up to and including 11 knots, an efficient survey
vessel will not generate noise which might induce avoidance reactions
in fish, beyond a distance of 20 m.
Designers of new research vessels will naturally make their own
decisions on noise characteristics and may opt for machinery with
limited noise reduction. It is however, the opinion of those who
drew up the recommendations, that propulsion systems should be avoided
which produce, at any operational speed, high levels of noise at
frequencies to which fish are sensitive. Such systems may be capable
of being noise reduced over a limited speed range around 11 knots
but, if they are likely to disturb fish at other speeds, the quality
of the survey results will be degraded.
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