Oceans of noise - Whale and Dolphin Conservation Society

2. More targeted studies into each form of noise pollution at a local level on thosepopulations or individuals exposed and potentially affectedConsideration should be given to all cetacean species when developing mitigation protocols,although it may not always be useful to apply data collected from one species, to another.Mitigation should be tailored to the needs of those suspected to be most vulnerable, both in termsof individuals (i.e. mothers and calves) and species (where status may be endangered, vulnerableor unknown).Because of the exceptional variety in marine mammal ears and the implication of this variety fordiversity of hearing ranges, there is no single frequency or combination of pulse sequences thatwill prevent any impact (Ketten 1998).Roberts and Wieting (2001) state that National Marine Fisheries Service (NMFS) decisionmakingunder high levels of uncertainty is an obstacle, and go on to state that scientific issuesinclude:1. A lack of standardised baseline data,2. A need for cumulative impact assessment,3. A need for a better understanding of the “biology of disturbance”,4. Population level effects and;5. Improved knowledge of the effects of noise on marine mammal prey species.Where observations recorded during mitigation procedures are adequately detailed, they mayprovide valuable baseline data that could better detail cetacean distribution, seasonality andabundance. Data may also be collected concurrent with attempts at mitigation to show whethermeasures are effective. Borggaard et al. (1999) state that the effects of anthropogenic noise maynot always be apparent even with control designs because of natural variation in dependantmeasures.A level of commitment to researching what is currently largely unstudied and presently unknown,but assumed to be true in the absence of statistically robust data, is needed. For example, detailedstudies on the efficacy of ‘ramp-up’, where the source of the noise is gradually introduced intothe marine environment in the hope that any animals in the vicinity will find the noise offensiveand leave the area, would be useful.Identification of a framework for long-term research and development programs with thepotential for closing identified information gaps would be an important step forward, as wouldenforcement of effective and comprehensive protection measures.7.2.3. Captive studiesAuditory studies have been conducted in captive environments on a limited number ofmanageable odontocete species. These are regularly applied to all species due to limited data.Ethical concerns aside, captive cetaceans are living in very different circumstances to that of wildcetaceans and there are likely to be gross inconsistencies in comparing the two. (See also section4.5).7.2.4. Measurement of hearing abilities in wild cetaceansStudies using portable instrumentation are conducted in the US to assess the hearing abilities inlarge cetacean species that cannot be kept in captivity. Recordings of physiological and, to date,70