WHAT DO WE KNOW ABOUT PIRATE PERCHES?

by Whit Gibbons

June 12, 2011

Jack Sparrow is certainly the most unusual pirate on the scene these days, but I recently encountered a different sort of pirate with its own intrigue. I caught two little fish in a flooded area of some nearby woods and recognized them as pirate perch. Knowing the name of a plant or animal is the first step in identifying it; knowing someone who can tell you about its lifestyle, its behavior and other interesting facts is the next step.

I caught the fish in a minnow trap, a small wire mesh cylinder with inward-pointing funnels at both ends. My grandson and I had placed some in a shallow woodland pool alongside a swampy area. We also caught other captivating creatures, including leopard frog tadpoles and some seldom-seen aquatic salamanders called sirens. We brought the fish home in a plastic sandwich bag filled with swamp water and I took them to a colleague who is an ichthyologist to confirm their identity and to find out more about their biology. Dean Fletcher, a research scientist at the University of Georgia's Savannah River Ecology Laboratory, probably knows more about pirate perches than any other living person, whether angler or fisheries biologist. The coauthor of a book on freshwater fishes, he has written one of the few modern scientific papers on pirate perches.

The pirate perch, a freshwater fish but not a true perch, is the only living species in its family. It is common and widely distributed along the Atlantic and Gulf coastal plains and up the Mississippi River Valley to the Great Lakes. But most people, even seasoned anglers, are not likely to see one. Adults are usually less than 4 inches long and are primarily nocturnal. In addition, not many people fish in small tributary streams, in weedy waters thick with root masses or in the floodplain swamps of larger rivers.

A bizarre biological trait of pirate perches involves the adult anatomy. As with other fishes, reproductive products (eggs and sperm) and body wastes are released through the vent, which is usually situated under the body near the tail. The vent is in this location in juvenile pirate perches. But as a pirate perch approaches adulthood, something strange happens. The opening gradually migrates along the underside of the fish until it is positioned under the throat, just behind the gills.

Fish biologists have speculated on the function of this odd placement of the vent since it was first described in 1824. As the scientific paper by Dean Fletcher and his colleagues says, "We solve[d] the conundrum through a combination of intensive field investigations, underwater filming, and molecular parentage analysis." In other words they studied the fish extensively in its murky habitat, filmed its behavior and used DNA analyses to see who the parents were of various offspring. Their discoveries were made in the cool waters of late winter and early spring when pirate perch begin spawning.

Through the use of modern technology, laboratory genetics and plain old-fashioned behavioral observations in the field, the scientists revealed why a fish would have a vent located in the front of the body instead of toward the back. They documented for the first time that the female actually thrusts her head into a tangled root mass and lays her eggs, a behavior unconfirmed for any other North American fish. The male quickly follows suit, putting his head into the same opening in the roots and depositing sperm to fertilize the eggs. The DNA analyses confirmed that particular offspring indeed had the parents predicted based on the mating observations.

My grandson and I released the two fish we had caught, still in good condition, back into their wetland home. Let's hope they find the right root masses to produce their young, leading to future generations of this unusual little fish. And why are they called "pirate" perch? If you put one in your home aquarium, it will apparently have no qualms about attacking smaller fish--to eat them, of course, not to take their money and jewels.

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