MARINE MAMMAL COMMISSION — Annual Report for 1995 



marine mammals to sound and pressure waves that, 

 depending on an animal's distance from the explosion, 

 may result in harassment, injury, or death. 



The Service published a proposed rule on 17 June 

 1993 to authorize the incidental taking of bottlenose 

 and spotted dolphins for five years. The Marine 

 Mammal Commission commented on the proposed 

 rule on 16 August 1993 and generally concurred with 

 the Service's conclusion that the removal operations 

 would have negligible impacts on bottlenose and 

 spotted dolphins, provided no animals were within 

 ranges that tissue and hearing damage could occur 

 when the explosives were detonated. However, the 

 Commission recommended that additional justification 

 be provided for the Service's determination that 

 pressure waves generated by the explosives would 

 dissipate to safe levels within 3,000 feet in all cases. 

 Also, the Commission noted that many marine mam- 

 mals other than bottlenose and spotted dolphins could 

 potentially be affected and recommended that the rule 

 also authorize the incidental taking of any marine 

 mammal that reasonably can be expected to occur in 

 the northern Gulf of Mexico. The Commission also 

 questioned a proposal to allow Service officials to 

 authorize the use of explosives when darkness or 

 weather conditions would impair the ability to detect 

 marine mammals in the vicinity of the structure. 



In addition, the Commission expressed concern 

 about the proposed monitoring and reporting require- 

 ments. It recommended that requests for letters of 

 authorization be required to provide more specific 

 information on how marine mammals near a structure 

 being removed would be detected and on the steps to 

 verify that no marine mammals were killed or injured 

 by the blasts. The Commission suggested that in 

 addition to visual surveys, acoustic monitoring might 

 help detect marine mammals in the blast area. With 

 respect to post-explosion monitoring, it suggested that 

 the Service periodically compare reports from holders 

 of letters of authorization with marine mammal 

 stranding data to check for possible correlations 

 between strandings and structure removals. 



Finally, the Commission noted that marine mam- 

 mals could be affected indirectly as well as directly by 

 structure removals. For example, hazardous substanc- 

 es deposited in sediments beneath oil platforms could 



be resuspended in the water column by explosions and 

 thus enter the marine food web. As top-level carni- 

 vores, dolphins would be particularly susceptible to 

 the accumulation of such substances. 



The Service published a final rule authorizing the 

 take of bottlenose and spotted dolphins on 12 October 

 1995. The authorization is for five years and allows 

 harassment of up to 200 dolphins per year. Some, but 

 not all, of the Commission's recommendations were 

 incorporated into the final rule. 



The Service believed that mathematical modeling 

 provided by the applicant was adequate to show that 

 injuries to marine mammals from the planned explo- 

 sions were highly unlikely and that further experi- 

 ments were unnecessary. The final rule, however, 

 limits the explosives that may be used to a pressure 

 level equivalent to a 50-pound charge. The Service 

 concluded that the probability of affecting cetaceans 

 other than bottlenose and spotted dolphins is remote, 

 given marine mammal survey data, and that other 

 species need not be covered by the authorization. The 

 final rule was expanded, however, to include both 

 species of spotted dolphins that occur in the Gulf, 

 Stenella frontalis and S. attenuata. It also was 

 modified to limit detonations to daylight hours and to 

 prohibit detonations when visibility prevented a pre- 

 detonation survey. The Service did not adopt the 

 recommendation that applicants provide additional 

 data on site-specific monitoring but did agree to 

 compare data from monitoring reports with marine 

 mammal stranding data. The Service also believed 

 that visual surveys were sufficient to detect marine 

 mammals in the vicinity of oil rigs and declined to 

 require acoustical monitoring. The Service concluded 

 that possible effects of resuspended hydrocarbons 

 would be temporary, localized, and unlikely to impact 

 marine mammals and their habitat. 



As of the end of 1995 only one letter of authoriza- 

 tion had been issued under the regulations. By 

 Federal Register notice of 5 December 1995, the 

 National Marine Fisheries Service announced that it 

 had issued a letter of authorization to the Murphy 

 Exploration and Production Company on 27 Novem- 

 ber, authorizing the taking of small numbers of 

 bottlenose and spotted dolphins incidental to rig 

 removal activities. 



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