Flow Reversal Events Increase the Abundance of Nontroglobitic Fish in the Subterranean Rivers of Mammoth Cave National Park, Kentucky

摘要

Mammoth Cave National Park (MCNP) is home to the longest cave system in the World and is dissected by the Green River, one of the most speciose watersheds on the continent. Cave springs create a direct aquatic link between subterranean waterways and the Green River. The history of these subterranean river systems is filled with eyewitness reports of various species of surface water (nontroglobitic) fishes, including introduced rainbow trout. This study documents the occurrence of Green River fish species in the cave system of MCNP. Four sites were sampled over a two year period using a variety of gears. In total, sampling yielded 1849 individuals (mostly larval/juvenile) of 22 species representing nine families. Of the 22 species, 12 have never before been documented in the cave environment. The effects of local hydrological events on the abundance of Green River fishes in the cave system were also examined. Catch per unit effort of larval fish was shown to be significantly higher following high water flow reversal events indicating that most individuals are accidentally washed into the cave environment. These fish likely influence energy flow in the cave ecosystem. Flow reversal is dependent on a dynamic between river stage and local ground water level. Releases from the Green River Dam, upstream of the park, influence river stage and therefore flow reversal events. In this way anthropogenic water control effects processes important to energy flow in the cave environment.