Grotto sculpin Cottus sp.
ESA status: endangered

Grotto sculpin pc A.J. Hendershott

Grotto sculpin are a unique population of sculpin endemic to caves in Perry County, Missouri. The small, pale, nearly-blind grotto sculpin may be the only population specially adapted to living in subterranean streams. Scientists first documented the grotto sculpin in 1991, and are in the process of formally describing it as a distinct species based on its morphologic and genetic uniqueness.

Grotto sculpin have been found in cave streams, resurgences (the place where a cave stream emerges from the cave system), springs, and two surface streams. The population has a higher percentage of juveniles on the surface, and a higher percentage of adults within the caves; juveniles use resurgences as nursery areas. Adults likely migrate into caves to reproduce. They feed mainly on invertebrates such as amphipods and isopods.

Perry County is known as one of the cave capitals of the United States, with more than 630 recorded limestone caves (or karsts). The area would appear to provide copious habitat for the grotto sculpin, but extensive surveys have found the fish in only five cave systems in two karst areas: Central Perryville and Mystery-Rimstone. These two areas encompass approximately 222 square kilometers – the entire known range of this rare fish. The grotto sculpin appears to be dependent on systems with consistent water flow, ample organic input, an abundance of invertebrates, and connections to surface streams to allow for seasonal migrations. Nearly all of the land within the known range of the grotto sculpin is privately owned.

Karst regions are unique in that numerous sinkholes allow chemicals and other pollutants to reach groundwater directly, without being filtered. Water pollution from numerous sources poses a significant threat to the grotto sculpin. Although it is illegal to dump waste in open sites in Missouri, at least half of the sinkholes in Perry County have been or are still being used as dump sites – household waste and chemicals, sewage, tires, dead livestock, and pesticide and herbicide containers have all been found in sinkholes. Runoff from agriculture, leaks from private septic systems, and contaminated runoff from roads all contribute to the pollutant load. In addition, predation by invasive fish poses a threat to the eggs and young of grotto sculpin. Predatory invasive fish including carp, fathead minnows, bluegill, and channel catfish were found in all of the caves occupied by the grotto sculpin. For a species with a naturally small population and limited range, these threats could easily spell destruction.

photo credit: A.J. Hendershott, Missouri Department of Conservation