The Marine Mammal Protection Act (MMPA) allows for specified persons to employ measures to deter marine mammals from damaging fishing gear and catch, damaging personal or public property, or endangering personal safety, as long as these measures do not result in death or serious injury of marine mammals. The MMPA directs the Secretary of Commerce, through NOAA's NMFS, to publish a list of ``guidelines'' for use in safely deterring marine mammals under NMFS' jurisdiction and to recommend ``specific measures,'' which may be used to nonlethally deter marine mammals listed under the Endangered Species Act (ESA). While the guidelines and specific measures are not mandatory, the MMPA provides protection from liability under the MMPA for take resulting from such deterrence measures by specifying that any actions taken to deter marine mammals that are consistent with the guidelines or specific measures are not a violation of the act. NMFS has not evaluated these deterrents for effectiveness. This rulemaking also includes prohibitions on certain deterrent methods that NMFS has determined, using the best available scientific information, would have a significant adverse effect on marine mammals.