What would you think if I told you a unique fish was marooned here in Missouri? Most of us associate islands with being marooned, so the notion of marooning a fish sounds absurd, right?
As silly as it may sound, the secretive spring cavefish is stranded, and its uniqueness is nearly as interesting as the story behind its distribution.
To understand this fish's story you need to know something about how it looks. Spring cavefish are roughly the size of an AA battery, but they're thinner and weigh less than a half dollar. They would make a meager meal for any decent-sized predator. Most of their time is spent underground, so this light brown fish's eyes are small and nearly useless. The other two cavefish species in Missouri, the Southern and Ozark cavefishes, are completely blind and colorless.
No longer built for sunlight, spring cavefish are not built for strong current. Fish enthusiasts know that deeply forked tails, like those on channel catfish, indicate a strong or fast swimmer. A fish with a rounded tail fin like the spring cavefish usually live in still or slow moving pools. Life in underground streams provide numerous places void of strong current.
Getting here by accident
It is this fish's helplessness in the current that explains how it was stranded, but to fully understand you need to look back in time about the time the last glaciers were melting (12,000 years ago). Man was beginning to enter North America, and the Mississippi River made a sharp turn south of Cape Girardeau and ran toward Poplar Bluff. Towns like Delta and Advance were in the former Mississippi River Channel.
You could walk from the Benton Hills of Missouri to the Shawnee Hills of Illinois without ever getting wet.
The network of caves and underground streams were connected and permitted cavefish to swim from Missouri's Benton Hills, 50 miles north and east into Illinois. They were all one big population.
Now fast forward about 8,000 years to the tribal mound building period (4,000 years ago). The Mississippi River broke through these hills at Thebes, Ill., occupying the channel we know today. Any cavefish found in Missouri's Benton Hills were separated from those fish found in Illinois.
Blind and poorly equipped for strong current, spring cavefish would never be able to cross the Mississippi. Even if they realized they were separated, any cavefish trying to navigate relentless river currents would likely never reach the eastern side. Thus, the spring cavefish lives within an isolated hill in Southeast Missouri, just south of Cape Girardeau.
Unaware of its isolation from other populations, spring cavefish rely on electro-sensors to navigate and find prey. Almost as bizarre, cavefish find prey with help of another sense: taste. By circulating water through their mouth, these small aquatic predators find invertebrates by taste, not smell.
It prefers to hunt underground but occasionally visits daylight pools that collect at the base of limestone bluffs. Known in Illinois, Kentucky and Tennessee, spring cavefish were first discovered in Missouri by Conservation Department fish biologist Bill Pflieger in 1976. If it were not for their habit of visiting those pools we may never have known they were here.
Quiet but important
Even though most of us will never see a spring cavefish, they are important to us for at least two reasons.
First, the fish's presence tells us that ground water quality is good. If that fish can't live in the ground water, we wouldn't want to drink it. Groundwater is polluted by sediment, trash, pesticides and animal waste. When sinkholes become a dumping ground they serve as a shortcut to groundwater. Whatever goes in a sinkhole ultimately affects the spring cave fish and people who use those underground streams to supply wells.
Second, the fish serves as a living clue to the land's history. By examining how the fish got where it is, we have clue to our past. This sense of place is an intangible devoid of monetary value. Southeast Missouri is a unique place to be treasured by all. Perhaps it takes a seemly insignificant fish to point that out.
Spring cavefish have been marooned in Missouri for nearly 4,000 years. Consider them a special feature to our wonderful part of the state and be glad they are here.
A.J. Hendershott is an area agent with the Missouri Department of Conservation.