OBJECTIVES 



1 . Summarize the data on underwater noise generated from offshore drilling activities. 



2. Summarize the data on underwater hearing capabilities of marine mammals. 



3. Estimate the possible impact of noise from offshore driUing operations and 

 associated human activities on natural populations of marine mammals. 



RESULTS 



1. Noise measurements from offshore drilling operations are sparse. Existing mea- 

 surements are limited in bandwidth and are variable. 



2. Some information is available on the underwater hearing sensitivity for a few 

 species of marine mammals. However, without direct measurement of a species it is 

 impossible to extrapolate to other species. 



3. Information on the effects of subcritical levels of noise on animals is incon- 

 clusive. The effects of noise on natural populations of marine mammals is largely anecdotal. 

 Therefore, the effects of offshore drilling noise on these animals based on present data can- 

 not be determined. 



4. No conclusions about the effects of stress on natural populations of marine 

 mammals has been verified under controlled conditions. 



RECOMMENDATIONS 



1. Measure the noise generated from current and future offshore drilling operations. 

 Include sensitive frequency ranges from known marine mammal audiograms. 



2. Identify lease areas where offshore oil development is anticipated. Identify 

 species of marine mammals that inhabit these areas. 



3. Identify lease areas where introduction of increased sustained noise might dis- 

 rupt a critical life cycle of marine mammals. For example, feeding, breeding, transit or 

 congregation areas. 



4. Initiate a monitoring program when a lease area is opened. Monitor both 

 acoustic and population parameters in the lease area as development progresses. 



5. Develop a program to monitor the effects of controlled introduction of noise to 

 a marine mammal population. Quantify the effects of the noise on the population. 



6. Obtain underwater audiograms of marine mammals that occur in the selected 

 lease areas. 



7. Determine the effects of noise on marine mammals under controlled conditions. 



H-5 



