The National Marine Fisheries Service (NMFS) is preparing a proposed rule to consider updated information informing the standards that underlie NMFS’ regulations governing the unintentional taking of marine mammals incidental to geophysical surveys in the Gulf of Mexico (GOM). The current regulations were issued on January 19, 2021 under section 101(a)(5)(A) of the Marine Mammal Protection Act (16 U.S.C. 1361 et seq .) in response to an application from the Bureau of Ocean Energy Management (BOEM) and set forth the permissible methods of taking; means of effecting the least practicable adverse impact on the affected species or stocks and their habitats ( i.e ., mitigation); and requirements pertaining to the monitoring and reporting of such taking. Letters of Authorization (LOAs) issued under the regulations authorize the take of marine mammals incidental to the specified activities for the remainder of the original 5-year period. The regulations became effective on April 19, 2021. This rulemaking will account for updated information that has since been provided to NMFS by BOEM. While processing requests for individual LOAs under the current incidental take regulations, NMFS discovered that the estimated incidental take from the proposed survey activities (annual and 5-year totals) that BOEM submitted in connection with a revision to its application had been miscalculated. As a result, take levels were reached much sooner than anticipated for some species. BOEM determined that it miscalculated the level of take when it reduced its scope of specified activity in March 2020 by removing the Gulf of Mexico Energy Security Act (GOMESA) moratorium area from the then proposed action. Generally, this miscalculation caused BOEM to underestimate the total predicted exposures of species from all survey activities. The practical effect of this is that the full amount of activity for which BOEM sought incidental take coverage in its application cannot be authorized under the current incidental take regulations. BOEM has provided NMFS with revised take estimates and an explanation of the miscalculation. Accordingly, NMFS is undertaking this rulemaking to adjust the take estimates and, provided the necessary findings can continue to be made, revise the current incidental take regulations as appropriate.