When the spring breeding season nears, the river rhumba begins. It is an eerie melody, heard in lakes and streams throughout Arkansas, and from the Great Lakes to the Gulf of Mexico. An angler on the water at night will often hear the peculiar combination of purring and grunting welling up from the depths and wonder about the sound’s origin.
I remember when I first heard it. I was 14. A friend and I were trotlining in east Arkansas’ L’Anguille River. It was near midnight. We had baited our lines and laid back in our boat to catch some shut-eye until it was time to check the lines again.
I felt the sound before I heard it. One hand rested on the boat’s metal bottom, and I was awakened by a curious vibration coursing through my fingertips. The vibration stopped, then started, then stopped again. I awoke my companion. “What’s that?” I asked, pressing his hand to the bottom of the boat. My friend was as bewildered as I was.
The sound grew louder. It was distinctly audible now, and in minutes, similar sounds were emanating from the water all around us. The bottom of the boat hummed as the deep notes passed through the metal molecules and set them atwitter.
We were not frightened by the noise, only curious. It was oddly soothing. Neither of us had ever heard such a sound, and though we knew it must originate from some type of aquatic animal, we did not know what kind. We listened throughout the night, intrigued by the strange notes carried in the current.
“What you heard is drum fish,” my uncle told me the next day. “When drum get ready to spawn in spring, the males make that sound to attract their sweethearts. It may not sound pretty to you and me, but to the drum, it’s a love song.”
My uncle, who spouted many tall tales about wildlife, was correct in this instance. The sound comes from the male gaspergou, or freshwater drum, croaking away as part of its mating ritual. A unique set of muscles contracts around the fish’s swim bladder, causing the air-filled organ to boom like a balloon rubbed with the fingertips. Fisheries scientists speculate that female drum, ready to spawn, swim toward the males they hear calling from a distance.
Some of the gaspergou’s common names — thunderpumper, croaker and bubbler — are derived from this exercise of voice. James Gowanloch commented in Fish and Fishing in Louisiana, “The members of this family are peculiarly able to produce quite vigorous sounds, so vigorous indeed that a school of drums, swimming past an anchored boat, can awaken a sound sleeper.” On Lake Winnebago, Wisconsin, the noise produced by big drum in June resembles “a motorcycle gang racing in the distance,” said one fisheries biologist there.
While fishing on the Rio Negro in Brazil a few years ago, I learned that drum aren’t the only fish that “sing.” Once again, I was fishing for catfish, this time with Walter Delazari, a friend from Sao Paulo. The sun was setting. As Walter and I waited for a catfish to find our bait, we laid back in our boat and watched hundreds of scarlet macaws flocking to a roost on the edge of the rainforest. The din created by these beautiful birds was almost deafening, but it was not loud enough to hide the sounds we soon heard coming from the river. They began abruptly, weird little chirps and warbles almost like singing frogs. But these sounds originated deep in the water beneath us. The volume rose as more and more of the creatures began to sing their strange paean, and soon the metal hull of the boat began vibrating.
“Que é isso?” I asked Walter in Brazilian Portuguese. What’s that?
A look of feigned fright crossed his face. “Espírito!” he said. Spirits!
It was only by coincidence that I learned the true origin of those sounds. While doing research on the Internet, I stumbled across a site about the 1993 Calhamazon Expedition, a scientific foray to study fish diversity in the Amazon River. By clicking on a link, I was able to hear the sounds of South America’s talking catfish recorded by expedition scientists. These fish create their loud croaking noises by grinding the base of their pectoral fin bones on their shoulder bones. Most, if not all, of the 80 to 100 species in this genus can “talk” in this manner. Among these are some true giants (4 feet plus), which must be mesmerizing to hear.
If you do a Google search for “talking catfish,” you can find several YouTube videos where you can hear the sounds yourself. They don’t sound like love songs to us, but to the whiskerfish,
they are.
The catfish found in Arkansas — channel cats, blues, flatheads and bullheads — can produce similar sounds by rubbing their pectoral fin bones against their swim bladder. Lift one from the water after hooking it, and it will seem to scold you with its weird croaking noises. This is called stridulation, a fancy term for the way some fish press their bones or teeth together to make noise. Think of the familiar way a cricket rubs its legs together to chirp.
On other websites devoted to the subject of fish acoustics, you can listen to sounds of the gaspergou’s saltwater relatives — the redfish, Atlantic croaker and black drum — and other fish such as the spotted seatrout, weakfish, silver perch and oyster toadfish. Listening to the singing of these fish using special underwater microphones, biologists can determine changes in their abundance from season to season and year to year.
The scientific aspects of fish songs are important, no doubt. But for some of us, the songs of fishes are nothing more than lullabies. On a recent catfishing trip on the Mississippi River, I lay in the bottom of my boat, my ear pressed against the hull, listening to the mating melodies of a thousand gaspergous. The river rhumba lulled me to sleep.