[This diary was originally posted to Daily Kos on July 7, 2006.]

Sitting in a boat on a still day, the ocean seems gentle, calm and most of all silent.  Even the song of a humpback whale, a sound that when produced by an individual off the coast of Newfoundland can be heard by another a couple of thousand miles away in Bermuda, goes unnoticed above the waves.  And yes, most marine animals, be they jellyfish, clams or sharks, make no sounds at all.

But there are some fish whose vocal abilities, when heard underwater, rival many songbirds, if not in tune at least in volume.  Fish that produce sound are called soniferous, and they encompass a surprisingly large minority of species. In fact there is one family of fish that are collectively known as "Drums", named for the pounding noise they make to attract mates or establish territories.

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The Black Drum, above, is an uncommon fish in Rhode Island, but is representative of this family of fishes. Listen to a Black Drum here.

Nearly all fish have a swim bladder, a gas-filled organ that helps to control its buoyancy.  A fish swimming through the water expends the least amount of energy when it is neutrally buoyant.  In other words, the animal's exertion is spent propelling itself forward rather than having to deal with the issue of sinking or floating at the same time.  The swim bladder expands or contracts with depth keeping the fish on a steady horizontal course. (Sharks lack a swim bladder, but most species use an oil-infused liver to create the same effect.)

But this organ isn't always just for buoyancy. It can also be used for producing vocalization. The swim bladder of a fish is actually a muscle and can be induced by the fish to twitch causing it to vibrate like the skin covering a musician's drum when struck by a drumstick.

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One species of soniferous fish found in New England is the toadfish (Opsanus tau). The swim bladder of this species is one of the fastest moving muscles known in the animal kingdom, able to twitch nearly 200 times per second. To give you some perspective, that is four times faster than the wingbeat of a hummingbird. Listen to a toadfish's call, it's kind of eerie.  There's no voicebox involved, this noise is created by the bladder alone.

When I first started collecting live sea animals, toadfish were pretty easy to find.  But in the early nineties most of Rhode Island's salt ponds were opened up to shellfishing.  This didn't affect most fish, but the defense mechanism of a toadfish is to lay low and camouflage itself among the shallow-water beds of eelgrass. This may protect it from natural enemies, but against the hordes of clam diggers, with their sharp-toothed bullrakes, it was deadly. I remember the first year my local salt pond was opened up. That whole summer I found dozens and dozens of dead toadfish washed up on the beach, killed by being impaled on the tines of the bullrakes.

I have a pet toadfish named Jabba, now nearly fourteen years old.  He was given to me by a friend at a NOAA lab that raises these fish to be used in space shuttle experiments. Because the vestibular system of the toadfish is so similar to our own, these fish are used to study the effects of microgravity on the inner ear. So Jabba was a rejected ichthyonaut and now has found a home with me, saved from a space flight and certain dissection. You can watch a very short movie of Jabba by clicking on his picture below. That's my hand stroking the fish, and as an aside, one of the dorsal spines contains a powerful toxin. Seriously, could this fish be any cooler?

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[Update: Since this essay was first posted, fourteen year-old Jabba has died of old age. Along with Violet the octopus, this makes two much-loved animals I've lost this year.]

Other diaries in this series can be found here.

Originally posted to Mark H on Thu Aug 30, 2007 at 06:03 PM PDT.

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