Oceans of noise - Whale and Dolphin Conservation Society

7. Solutions – mitigation and managementSarah Dolman“To fully address the adverse effects of noise on the marine environment, it will also benecessary to look at the long-term impact onAppreciating this, acoustic pollution in the marine environment is clearly an issue whosesolution remains to be found in the coming decades” (Dotinga and Elferink, 2000).The reality is that little is known about the full consequences of noise pollution for cetaceans,particularly in the longer term. The various mechanisms by which marine mammals can beadversely impacted indicate considerable subtlety in the range of interactions, and a great deal ofadditional effort is required before we can expect to predict and quantify the potential for damageto populations (Potter and Delory 2001). Physiological impacts, as a result of exposure to noisepollution, are almost impossible to study. We currently rely on stranded or bycaught animals and,subsequently, analysis of ears and internal organs, to assess such impacts.With this limited knowledge, preventing impacts of noise pollution completely is unlikely, shortof bringing to an end those activities responsible for producing intense noise. This situation hasled to the pursuit of mitigation procedures suitable to minimise observable and short termbehavioural impacts, with the aim of reaching commonly acceptable standards.Mitigation measures are operational techniques designed to reduce the adverse impact on thespecies or stock and its habitat (Roberts and Hollingshead 2002). Specific measures imposedupon an activity to reduce these impacts will vary depending on the nature and scale of the noiseproduced, and on the nature of the activity itself.There are little baseline data on the effectiveness of any mitigation measures (Moscrop and Swift1999). This is emphasised by the non-uniform way in which sound travels through water (seeChapter 2) and the differing requirements and susceptibilities of different cetacean species,individual members within those groups and the activities being undertaken.Further, cetacean biology and behaviours are difficult to study and interpret. Ljungblad et al.(1988) noted that determining when subtle behavioural changes occurred was the most difficultpart of experimental observations. The significance of behavioural responses is also often open tointerpretation and debate. Likewise there can be debate about what is actually observed andrecorded. Details of observations may depend on many elements including observer skill, natureof observation platform, observation conditions (such as weather and sea state) and whetheracoustic as well as visual methods are used. In addition, measurements themselves may not besensitive enough to detect effects (Borggaard et al. 1999).It remains that those using loud sources are typically the most likely to be those in a position tofund forums of discussion about such impacts and investigate mitigation techniques, as well asfund research studies. However, this may restrict academic freedom and lead to a perception ofbias (Whitehead and Weilgart 1995), and ensuring that independent, non-aligned studies areconducted is likely to be a step towards finding solutions.68