Oceans of noise - Whale and Dolphin Conservation Society

acoustic measurements have been made on a few stranded or rehabilitated cetaceans (Ridgewayand Carder 2001).Caution should be encouraged in the use of captive or stranded (and therefore compromised)animals to obtain data.7.2.5. Software modelsComputational models of whale auditory sensitivities, such as the humpback whale hearingmodel (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 whalewatching (Erbe and Farmer 2000).A spatial model of collision risk has been developed (Tregenza et al. 2000). This model hasidentified that mitigation procedures are urgently required. For example, the model indicates thata population of short finned pilot whales off the Canary Islands is at risk of extinction fromcollisions, unless consistent and effective mitigation action is carried out.Autopsied animals, and computational studies that do not require the use of trained or wildcetaceans, should be used wherever possible to obtain auditory data. Correlational studies, such ascorrelations of strandings with increases in noise levels or military manoeuvres, are generallypreferred to experimental ones (Whitehead and Weilgart 2001).7.3. Long-term impactsHESS (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 aneffect that could impact a population over the longer term. It generally remains difficult to detectthese 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 benecessary to adjust the boundaries or zones over time as, for example, cetacean distributions changewith oceanic conditions. With larger overall protection areas, it can be easier to adjust or move theboundaries of the core reserve or critical habitat zones. One precautionary tool is the marineprotected area, where core components of highly protected areas should ideally be nested within anetwork of multi-zone areas.There has been an increase in the number of forums held specifically for discussion of noiseimpacts to cetaceans and suitable mitigation procedures in recent years. The majority of theseforums 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 thecase for some military activities (see Gisiner 1998). Other forums have looked more generally atthe issue of noise pollution and cetaceans (see, for example, NZ 1996; JASA 2001; 2000).7.4. Cumulative impactsThe cumulative impacts of noise pollution should be considered alongside individual mitigationmeasures for a particular activity, or part of that activity. For example, there are often rules forwhale watch vessels, limiting the number of vessels at one time, and designating a larger distanceof protection around the animals as the number of vessels increases (see Annex 2A for anexample of detailed whale watching guidelines).71