Yes. If the boat or dock is yours, federal law lets you scare a sea lion off it with an air horn. The Marine Mammal Protection Act (MMPA) allows non-lethal deterrence by property owners, and NOAA Fisheries lists horns among the noise makers people have used successfully. The limits matter, though: who may do it, where, which species, and how. Get any of these wrong and a legal hazing turns into an illegal "take."
The Short Answer: Your Property, Non-Lethal, No Injuries
The MMPA bans "taking" marine mammals, and its definition of harassment is broad. Under 16 U.S.C. 1362(18), harassment includes any act of pursuit, torment, or annoyance that has the potential to disturb a marine mammal by disrupting its behavior, including resting and sheltering. So a horn blast at a sea lion sleeping on a public jetty can count as illegal harassment.
The exception is in 16 U.S.C. 1371(a)(4)(A). It allows four groups to deter a marine mammal, "so long as such measures do not result in the death or serious injury of a marine mammal":
- The owner of fishing gear or catch (or their employee or agent), to protect the gear or catch.
- The owner of other private property (or their agent, bailee, or employee), to stop damage to that property.
- Any person, to stop a marine mammal from endangering personal safety.
- A government employee, to protect public property.
A sea lion on your swim step, a seal hauled out on your private float, or a pinniped trying to climb into your cockpit all fall under the property exception. An air horn makes noise and does not touch the animal, which is the kind of non-lethal tool the law has in mind.
Who Can Use a Horn, and Where
NOAA's West Coast Region spells out how the exception works on the water in its Deterring "Nuisance" Pinnipeds guidance. The table below summarizes it.
| Situation | Can you deter with a horn? | Notes |
|---|---|---|
| Sea lion on your own boat or private dock | Yes | Only the owner, or someone acting for the owner, may deter to prevent damage. |
| Marina floats and slips | The marina owner, staff, or agent | A slip renter should ask the marina office before hazing animals off the marina's floats. |
| Fishing boat with gear in the water | Yes, while actively fishing | The fishing exception covers gear and catch only while you are fishing. |
| Public beach, breakwater, or jetty | No | The MMPA does not let private citizens deter marine mammals from undeveloped or public property. |
| Animal threatening a person | Yes, anyone | Personal safety is the one exception that covers every person. |
| ESA-listed species | Only for personal safety | Includes the western stock of Steller sea lions (Alaska, west of 144°W) and Hawaiian monk seals. |
NOAA's West Coast guidance names the non-listed species you may deter from property: California sea lions, Pacific harbor seals, northern elephant seals, northern fur seals, and the eastern U.S. stock of Steller sea lions. In most of Alaska and all of Hawaii, the default answer is to leave the animal alone unless someone's safety is at risk.
What NOAA Says About Air Horns Specifically
Two NOAA documents mention horns by name.
The West Coast "Potential Methods" sheet (updated October 2018) lists "horns, whistles, bells" under Noise Makers for private property owners. It also lists "horns, bells, whistles" as an extra option for fishermen. NOAA adds an important caveat: these are not "approved" methods, just examples of methods that have worked against pinnipeds in the past. The same sheet lists methods to avoid: live ammunition, sharp objects, entangling devices, striking animals or ramming them with boats, poisons, and guard dogs.
The national deterrence guidelines were proposed in the Federal Register on August 31, 2020 (85 FR 53763). For non-ESA seals and sea lions, they place "air horns, in-air noisemakers, sirens, and whistles" under the guidelines column of non-impulsive acoustic deterrents. NOAA's fact sheet uses air horns as its example of a non-impulsive sound, the type it describes as less likely to affect hearing sensitivity than impulsive sources such as seal bombs. NOAA also recommends starting with less impactful tools, including in-air noisemakers, before moving to anything more aggressive.
The catch is that the guidelines are still proposed. NOAA's rule page still listed the action as a proposed rule when it was last updated on 09/19/2024. Under 1371(a)(4)(B), only actions consistent with published final guidelines get automatic protection from liability. Until the rule is final, your protection comes straight from the statute: deter only in the situations listed above, and do not kill or seriously injure the animal. The proposed rule also lists general prohibitions that make sensible ground rules now:
- Never target a pup.
- Never push a deterrent into the middle of a group.
- Never haze an animal that is charging, lunging, or vocalizing at you unless your safety is at stake.
- Never chase pinnipeds with a boat.
How to Haze a Sea Lion Off Your Dock With a Battery Horn
A portable train horn fits this job well because it needs no wiring, compressor tank, or dock power. It runs on the same cordless tool pack you already charge for your drill. Here is a routine that keeps you inside the rules:
- Block access first. NOAA strongly encourages avoidance before deterrence. Its lists include swim step protectors, bull rails, closely spaced posts, and fencing. A barrier works around the clock, and a horn only works while you are there to sound it.
- Stay back. NOAA's viewing guidance is to stay at least 50 yards from seals and sea lions. You don't have to walk up to the animal, because the horn's sound covers the distance.
- Use one long blast, then wait. Give the animal a clear exit to open water. If it slides off, you're done.
- Check for pups and aggression. If a pup is present, or the animal is barking and lunging at you, back off. Hazing an aggressive animal is allowed only when someone's safety is at risk.
- Combine it with other tools. NOAA's own lists pair noise with barriers, water spray from hoses and sprinklers, and visual repellents such as flags and strobes. Rely on more than one method.
For a dock that keeps getting visitors, a wireless remote makes a big difference. You can mount the horn at the end of the float, aim the trumpets out over the water, and trigger it from the deck or the house. Our horns pair with handheld remotes, and the Long-range Remote is rated up to 2000 ft.
For loudness, the tiers run from Dual (130 dB) to Quad (140 dB) to Extreme and Boss Series (150 dB and up). On a big float or a breakwater-side slip where the animals haul out farther away, the Extreme Series Train Horn for Milwaukee® 18v Battery is the one we'd pick. It runs on any Milwaukee® M18™ pack, so the batteries you already own for your tools keep it powered on the dock. For a single slip at close range, a Dual or Quad tier is plenty, and quieter for your neighbors. If the same horn rides in your pickup between trips to the marina, our best train horns for trucks roundup compares the full lineup.
For mounting ideas on rails and decks, see our pontoon boat train horn guide. For a broader comparison of on-water horns, see the best train horns for boats.
Penalties, Noise Rules, and Signals to Avoid
Using a horn outside the exceptions, such as blasting sea lions off a public jetty or hazing an endangered monk seal, is an MMPA violation. Under 16 U.S.C. 1375, the civil penalty in the statute is up to $10,000 per violation. Each unlawful take counts as a separate offense. A knowing violation is a crime, punishable by a fine of up to $20,000 per violation, up to one year in jail, or both.
Federal law also isn't the only rule. NOAA's West Coast page notes that loud noise or pyrotechnics may be restricted by local ordinances, and that you are responsible for checking local, state, and federal rules. Many marinas have their own quiet hours, so read your slip agreement.
On the water, the Inland Navigation Rules treat at least five short, rapid blasts as the danger or doubt signal (33 CFR 83.34). Any attention signal must be one that can't be mistaken for an authorized signal (33 CFR 83.36). Hazing at the dock with a single long blast avoids sending a false message to boats in the fairway. Our USCG sound-signal guide covers when a battery horn can also count as your required signaling device. Aim the trumpets away from people and wear hearing protection. The hearing safety guide lists safe distances.
FAQ
Is it legal to use an air horn on sea lions?
It is legal on your own boat, dock, or other private property, while you are actively fishing, or when an animal threatens someone's safety, as long as the animal is not killed or seriously injured. It is not legal on public beaches or breakwaters, or against ESA-listed species except for personal safety.
Has NOAA approved air horns for sea lions?
Not formally. NOAA's 2018 West Coast sheet lists horns as a method that has worked in the past, not an "approved" one. The 2020 proposed guidelines put air horns on the guidelines list for non-ESA seals and sea lions, but that rule has not been finalized.
Can I haze a sea lion off a public dock or a jetty?
No. Only the property owner, their agents or employees, or a government employee can deter animals from that property. If sea lions are taking over a public dock, call the harbor office or NOAA's regional office.
What about seals in Hawaii or Alaska?
Hawaiian monk seals and the western stock of Steller sea lions are ESA-listed. You may deter them only to protect personal safety, not to protect a boat or dock.