It was a beautiful morning on Isle du Bois Creek. My crew and I had just pulled up to a stream crossing in Jefferson County. We donned waders and prepared our gear for the day’s work: fish sampling. I took in the clear, slow moving stream and wondered, “What will we find today?” Electrofishing, we walked slowly upstream netting the stunned fish. We placed them in a holding net where they recovered and awaited identification. Later that morning my fellow biologist, Danny Brown, sorted fish and called out species names while I tallied them on a data sheet, “stoneroller, bleeding shiner, green sunfish,” the usual customers for a stream in this area. Suddenly the sorting stopped. Danny held up a fish and looked at me. My eyes widened in surprise as we exclaimed in unison “pirate perch!”
The pirate perch (Aphredoderus sayanus) is a perch in name only. It is unrelated to fish in the perch family, such as walleye. In fact, the pirate perch has no relatives at all; it is the only species in its family. In Missouri, the pirate perch is most abundant in the Bootheel area. My excitement at finding a pirate perch is owed to the fact that one has never been found in Isle du Bois or any neighboring creeks. This news is probably not front-page material, but to a fish enthusiast it’s pretty awesome.
Superficially, pirate perch seem unremarkable. They are a speckled purplish-black color and only grow to 4 or 5 inches in length. What really sets the pirate perch apart is its anus, specifically the location of its anus at the base of its gills. For decades biologists were puzzled by this odd feature. It was widely speculated that the anus (along with the reproductive opening) is close to the head because pirate perch are mouth brooders (a spawning behavior in which eggs are carried in the mouth until they hatch). Because of their secretive, nocturnal nature this theory was never confirmed. Happily, for curious people like me, recent research has unraveled the mystery — pirate perch are not mouth brooders. Their strangely placed urogenital opening is adapted for a method of reproduction that was completely unknown. Researchers actually had to make up a word for it: transbranchioral spawning. It works like this. The female noses her way into a dense mass of underwater roots. As she releases her eggs, they collect in her gill chamber. She then forces them out through her mouth. In this way the eggs are “injected” deep within the root mass where they are sheltered from strong current and predators. The female backs out of the roots, then the male enters and fertilizes the eggs using the same method.
After showing our unusual catch to the rest of the crew, we release him back to the creek and watch as he darts under a root wad. The unexpected discovery reminds me why I got into this field. The question “What will we find today?” sometimes has a fascinating answer.
—Story by Sarah Peper, photo by Danny Brown
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