Oceans of noise - Whale and Dolphin Conservation Society

acoustic measurements have been made on a few stranded or rehabilitated cetaceans (Ridgeway
and Carder 2001).
Caution should be encouraged in the use of captive or stranded (and therefore compromised)
animals to obtain data.
7.2.5. Software models
Computational models of whale auditory sensitivities, such as the humpback whale hearing
model (Helweg et al. 2000) may be of assistance in determining cetacean sensitivity to sound.
Software models to estimate the potential effects of noise impacts have proved valuable for whale
watching (Erbe and Farmer 2000).
A spatial model of collision risk has been developed (Tregenza et al. 2000). This model has
identified that mitigation procedures are urgently required. For example, the model indicates that
a population of short finned pilot whales off the Canary Islands is at risk of extinction from
collisions, unless consistent and effective mitigation action is carried out.
Autopsied animals, and computational studies that do not require the use of trained or wild
cetaceans, should be used wherever possible to obtain auditory data. Correlational studies, such as
correlations of strandings with increases in noise levels or military manoeuvres, are generally
preferred to experimental ones (Whitehead and Weilgart 2001).
7.3. Long-term impacts
HESS (1997) stated that behavioural effects of concern related to feeding, social behaviour,
migration, avoidance and abandonment of critical habitat. Changes in these behaviours could have an
effect that could impact a population over the longer term. It generally remains difficult to detect
these changes and therefore designation of certain critical areas as sacrosanct is urgently required.
Unlike land-based critical habitat, marine critical habitat is likely to be less fixed. Thus, it may be
necessary to adjust the boundaries or zones over time as, for example, cetacean distributions change
with oceanic conditions. With larger overall protection areas, it can be easier to adjust or move the
boundaries of the core reserve or critical habitat zones. One precautionary tool is the marine
protected area, where core components of highly protected areas should ideally be nested within a
network of multi-zone areas.
There has been an increase in the number of forums held specifically for discussion of noise
impacts to cetaceans and suitable mitigation procedures in recent years. The majority of these
forums have been focused on activities that propagate over large ocean areas, for example,
seismic activities (see HESS 1997; etc) and even outside the dominion of national EEZs, as is the
case for some military activities (see Gisiner 1998). Other forums have looked more generally at
the issue of noise pollution and cetaceans (see, for example, NZ 1996; JASA 2001; 2000).
7.4. Cumulative impacts
The cumulative impacts of noise pollution should be considered alongside individual mitigation
measures for a particular activity, or part of that activity. For example, there are often rules for
whale watch vessels, limiting the number of vessels at one time, and designating a larger distance
of protection around the animals as the number of vessels increases (see Annex 2A for an
example of detailed whale watching guidelines).
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