The Marine Mammal Protection Act at 16 U.S.C. Section 1371 Imposes a Moratorium on the Take of Marine Mammals and Provides That Incidental Take by Harassment May Be Allowed Only Upon Request From a U.S. Citizen Engaged in a Specified Activity, the National Marine Fisheries Service Predicts Level B Harassment From Impulsive Sound at Received Levels Above 160 Decibels Referenced to One Micropascal, the Sperm Whale Produces Echolocation Clicks With a Maximum Recorded Source Level of 236 Decibels, Seventy-Six Decibels Above the Threshold and Squarely Inside the Operating Range of the Licensed Seismic Airgun Arrays the Service Regulates, Each Animal Spends More Than Eighty Percent of Its Life Echolocating at Depths Routinely Exceeding Four Hundred Meters, No Whale Has Ever Filed an Application, None Has Ever Been Issued an Authorization, and the Largest Unlicensed Seismic Survey Operation in American Waters Has Been Running Continuously Since Before the Moratorium Took Effect on October 21, 1972

I. The Moratorium

On October 21, 1972, the Marine Mammal Protection Act became law as Public Law 92-522. Section 101(a) of the Act, codified at 16 U.S.C. section 1371(a), established a moratorium on the taking of marine mammals in waters under the jurisdiction of the United States, a term the statute defines to include the territorial sea and the 200-nautical-mile Exclusive Economic Zone.¹

The Act defines its key term with unusual breadth. “Take” means “to harass, hunt, capture, or kill, or attempt to harass, hunt, capture, or kill any marine mammal,” under 16 U.S.C. section 1362(13). Harassment itself is defined in two levels. Level A harassment covers acts with the potential to injure. Level B harassment covers “any act of pursuit, torment, or annoyance which has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering,” under 16 U.S.C. section 1362(18)(B).¹

The moratorium is not absolute. Section 101(a)(5)(D) provides the mechanism by which an operator may lawfully proceed: upon request, the National Marine Fisheries Service may allow the incidental, but not intentional, taking by harassment of small numbers of marine mammals by U.S. citizens engaged in a specified activity, other than commercial fishing, within a specified geographic region, provided the Service finds the total taking will have a negligible impact on the species or stock. The implementing regulation, at 50 CFR 216.101, repeats the formula nearly verbatim: the mechanism exists for allowing, upon request, the incidental taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity. Authorizations issued under this provision, known as incidental harassment authorizations, run for periods of up to one year.²

II. The Threshold

The Service has published the numbers at which an impulsive sound becomes a predicted take. In its acoustic guidance, NMFS predicts that marine mammals are likely to be behaviorally harassed in a manner that qualifies as Level B harassment when exposed to underwater noise above root-mean-square received levels of 120 decibels referenced to one micropascal for continuous sources, and 160 decibels referenced to one micropascal for nonexplosive, impulsive sources, a category the guidance illustrates with the example of seismic airguns. The thresholds date to 2005 and appear, unchanged, in the Service’s October 2024 summary of acoustic thresholds.³

One hundred and sixty decibels is therefore the line. Above it, an impulsive sound in American waters is, in the agency’s own predictive framework, a take by harassment, and any operator producing it needs the paper described in Section I.

III. The Licensed Fleet

Seismic airgun arrays, the sound sources the guidance names as its example, are formidable instruments. Full-scale arrays produce source levels of 248 to 255 decibels referenced to one micropascal at one meter, zero-to-peak, according to a study published in Scientific Reports, and broadband peak-to-peak source levels of 230 to 255 decibels are reported for airgun arrays in the survey literature. They fire every 5 to 20 seconds, sweeping the seafloor for hydrocarbon exploration and scientific mapping.⁴

The operators of these arrays file the applications. The Service has issued incidental harassment authorizations for seismic surveys to oil and gas operators, including the 2015 authorization for an exploration drilling program in the Chukchi Sea, and to university research fleets, including the National Science Foundation-funded surveys led by the Scripps Institution of Oceanography in the South Atlantic in 2018 and the Northeast Pacific in 2019. The licensed operator submits an application, accepts mitigation measures such as exclusion zones, soft starts, and protected-species observers, and reports the takes.⁵

The system works, for those who use it. The file for each survey contains the request, the negligible-impact finding, and the authorization. The paper exists.

IV. The Operator

The sperm whale, Physeter macrocephalus, is the largest of the toothed whales and a deep diver found throughout the ice-free waters of the globe in depths greater than 1,000 meters. Whitehead’s 2002 global estimate, cited in the National Marine Fisheries Service’s five-year review as the best available figure, places the worldwide population at approximately 300,000 to 450,000 animals. The species has been listed under the Endangered Species Act since that statute was enacted in 1973, and it has been protected under the Marine Mammal Protection Act since 1972, the year the moratorium took effect.⁶

Each animal is a formidable forager. An adult sperm whale ingests roughly one ton of squid per day on average, migrating year-round over large distances in search of food, and it locates that food the way a survey vessel locates oil: by ensonifying the water column and reading the returns.⁷

V. The Equipment

While foraging, the sperm whale produces short-duration sound signals called usual clicks in a frequency band of 10 hertz to 30 kilohertz. The clicks are directional, projected in an intense forward-directed beam, and the maximum recorded source level is 236 decibels referenced to one micropascal at one meter, measured by Møhl and colleagues in 2003. The figure makes the sperm whale’s biosonar the loudest in the animal kingdom. The off-axis low-frequency components of a single click can be detected at distances of 15 kilometers in sea state 3.⁷

Set beside the licensed fleet, the equipment is competitive. The whale’s 236 decibels sits inside the 230-to-255-decibel operating band reported for seismic airgun arrays. The survey vessel fires every 5 to 20 seconds. The whale’s inter-click interval during descent varies from 0.5 to 2.0 seconds. The whale surveys faster than the fleet.⁴⁷

The whale’s 236 decibels sits inside the operating band of the licensed seismic fleet. The whale surveys faster than the fleet.

VI. The Survey Pattern

The operation runs on a demanding schedule. Sperm whales typically spend more than 80 percent of their time immersed in foraging processes. The foraging dives routinely exceed a depth of 400 meters, sometimes reach more than 2,000 meters, and last 30 to 40 minutes. During descent the animal emits its usual clicks at intervals of 0.5 to 2.0 seconds; as it closes on prey it switches to creak clicks, rapid pulse trains equivalent to the terminal buzzes of echolocating bats. Tagging data from the Atlantic have recorded maximum foraging depths of 1,200 meters in average water depths exceeding 2,000 meters.⁷⁸

Every dive is a survey line. The clicks ensonify the water column, the echoes return from squid aggregations, and the animal adjusts its acoustic gaze to the density of the targets. The coverage is continuous, the duty cycle is relentless, and the Service has never received an application describing any of it.

VII. The Enforcement Arithmetic

The face-value comparison is stark. The Level B threshold for impulsive sound is 160 decibels. The whale’s maximum recorded source level is 236 decibels. The difference is 76 decibels, which corresponds to roughly forty million times the acoustic intensity of the threshold. The statute’s penalty provision, 16 U.S.C. section 1375(a)(1), provides that any person who violates the subchapter may be assessed a civil penalty of not more than $10,000 for each violation, and that each unlawful taking shall be a separate offense.³⁹

The throughput of the operation converts readily. At roughly one click per second across the more than 80 percent of the day spent foraging, a single animal produces on the order of seventy thousand clicks per day. Were each click counted as a take, the theoretical daily exposure for one whale would run to roughly $690 million, before the separate-offense rule is applied across the estimated 300,000 to 450,000 animals operating worldwide. The arithmetic, like the tide tables in the water-diversion matter, leaves the realm of the routine.⁶⁷⁹

Seventy-six decibels above the threshold. Roughly forty million times the acoustic intensity. No application has ever been filed.

VIII. The Defense

The defense must be stated plainly, as this publication’s convention requires. The authorization mechanism of section 101(a)(5)(D) is available, by the regulation’s own terms, to U.S. citizens who engage in a specified activity, upon request. A sperm whale is not a U.S. citizen. It has not requested anything, and the Service maintains no application form that a whale could file and no procedure by which it could receive one. The take prohibition of section 101(a) binds “persons,” and section 1362(10) defines “person” as private persons and entities and the officers, employees, agents, departments, and instrumentalities of governments, a list that contains no cetaceans.²¹

There is also the matter of what an authorization authorizes. An incidental harassment authorization permits take that is incidental to a specified activity: the survey is the activity, and the harassment of the whale is the incidental consequence. In the sperm whale’s operation the clicks are not incidental to the foraging. The clicks are the foraging. There is no specified activity to which the sound is incidental, no applicant to name in the negligible-impact finding, and no one-year period after which the authorization could expire, because the operation has no start date. It predates the moratorium by millions of years.²

And there is the irony the file cannot avoid. The sperm whale has been protected under the Marine Mammal Protection Act since 1972. The Act’s oldest protected class is, by the agency’s own numbers, its largest unpermitted seismic operator. The law reaches the operator. It does not reach the ocean.⁶

The law reaches the operator. It does not reach the ocean.

IX. Conclusion

The Marine Mammal Protection Act, effective October 21, 1972, imposes a moratorium on the take of marine mammals in waters under U.S. jurisdiction, defining take to include harassment and Level B harassment to include any act with the potential to disturb a marine mammal by disrupting its behavioral patterns. Incidental take by harassment may be allowed only upon request from a U.S. citizen engaged in a specified activity, with a negligible-impact finding, for periods of up to one year.

The National Marine Fisheries Service predicts Level B harassment from impulsive sound at received levels above 160 decibels referenced to one micropascal, a threshold written with seismic airgun arrays in mind. The sperm whale produces echolocation clicks with a maximum recorded source level of 236 decibels, seventy-six decibels above the threshold, inside the operating band of the licensed arrays, at a firing rate several times faster than the survey fleet’s, for more than 80 percent of every day, at depths routinely exceeding 400 meters.

No whale has ever filed an application. None has ever been issued an authorization. The largest unlicensed seismic survey operation in American waters ensonifies the deep ocean on a schedule no agency publishes and no statute reaches.

Ergo.