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More Species of the
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In a narrow band, 24 miles east to west, of limestone running from Bluespring Caverns in Lawrence County, Indiana south to Mammoth Cave in Kentucky, the northern cavefish is found. Along with cave crickets, cave crayfish, and cave beetles this cave-restricted creature lives in an environment devoid of light and deprived of most nutrients. Cavefish lack eyes, but are sensitive to light and vibrations caused by disturbances in their watery environment despite the fact that where cavefish dwell they represent the top of the food chain. Cavefish feed on tiny invertebrates found in the underground rivers below our feet and have a low metabolic rate that allows them to live for long period of time on fat reserves.
Endangered in the state of Indiana, the northern cavefish is suffering for several reasons. As with many endangered animals, this species is limited to a small subset of caves and is naturally found in low densities in any one of those. Their habitat requirements are threatened by silting and flooding, the result of increased impervious surfaces, deforestation, and sinkhole disturbances. Cave rivers are simply underground versions of the surface streams we monitor for water quality. In its restricted habitat, it is easy to understand how one accidental spill or sinkhole disturbance could decimate an entire cave’s population of cavefish. No one would think of dumping a ton of dirt directly into a surface stream, but sinkholes are a direct conduit for such activity when they are used as stormwater diversions and dumping grounds.
The cavefish’s anomalies have a history of invoking detriment as in the 1800’s when cavefish were exploited for sale as souvenirs in fish bowls. Thankfully the tradition didn’t take hold and the species is still viable in about 4,300 caves. My personal experience with this animal came on a cold fall day several years ago when I was invited to help confirm whether or not a report of cavefish in an Orange County cave was legitimate. Clad in insulated hip waders off I went.
As with many experiences I seem to find myself in, the supposedly sufficient waders couldn’t begin to stand up to the gravel on which we crawled or the water in which we swam. The shockingly cold experience was all worth the pain as at least three individuals (considered indicative of a sizable population) were caught, weighed, and measured that day. I now have a greater appreciation for every report of cavefish I see because I know someone searched the watery depths most of us do not see or think of, even though we, unlike this remarkable fish have two functional eyes!
Nature picture credits (top to bottom, left to right): Photo © Keith Pamper.
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