The Noisy Plainfin Midshipman

There are many hazards of the sea. One of the least dangerous, yet still highly annoying and somewhat mysterious is the loud humming sound heard coming from the sea on summer nights by residents of coastal towns, in boats or in houses near the shore. The hum has been described variously as similar to the drone of a B-29 bomber or a giant electric shaver.

It is unclear how long this subsea hum has been keeping coastal dwellers awake, but in 1985, after complaints from houseboat dwellers in Sausilito, California, volunteers from a local aquarium found the answer.

As reported in the Christian Science Monitor of August 1985: ``It’s not a military secret,” says John McCosker, director of the Steinhart Aquarium. “It’s not the sanitation district. It’s not the Army Corps of Engineers. It’s not an extraterrestrial, a nuclear device, or a Russian submarine.” Most likely, he says, it’s the singing toadfish, also known as the plainfin midshipman.

During mating season in summer — which corresponds to the time houseboat dwellers usually complain — the male toadfish burrows into the mud of estuaries and bays, then starts droning out for female companionship. The drone comes from muscle contractions around the swim bladder.

With the mystery solved in Sausalito, the ominous hum appeared 800 miles north in Seattle, Washington in 2012.  Residents of West Seattle had been complaining of a load and disturbing hum from the sea that kept them awake at night.  A recording was made of the hum, which was identified as the mating call of plainfin midshipman fish.

Now, the Telegraph is reporting that in Southhampton, England there is a ” noise, which residents say ‘pulsates’ through their homes, starts at about 10pm and carries on all night, forcing some people to move away from the area because they find it impossible to sleep. Scientists believe the noise could be being caused by [plainfin midshipman] fish having sex in an estuary nearby in Hythe, near Southampton in Hampshire.”

The plainfin midshipman, also known as the singing toad fish, lives in deep waters for most of the year.  It is covered with hundreds of photophores along its body which are used to produce light for attracting prey as well as for camouflage. In the summer months, the fish swim up into extremely shallow waters, including the intertidal regions, to mate.  The fish can breathe through its skin so it can survive even when the tide goes out.

For a fish with no vocal chords, the fish are extremely noisy. The plainfin midshipman are noctural. The male fish contract the muscles near their swim bladders to create their distinctive hum. Often many males compete for the attention of females, their hums forming a loud chorus that can be heard on land or through the hulls of boats.

What is the best solution to cope with the nocturnal drone of the mating midshipman fish?  Unfortunately, the best answer is probably earplugs.

The Plainfin Midshipman

Thanks to Alaric Bond for contributing to this post.