The Influence of Acidic Runoff Episodes on Slimy Sculpin Reproduction in Stone Run

Abstract

Much research has been devoted to the effects of acidic runoff episodes on populations of brook trout Salvelinus fontinalis. Less is known about slimy sculpin Cottus cognatus and why their numbers have declined in acidified streams. Adult tolerance of low pH and aluminum (Al) toxicity is similar in these two species. Slimy sculpin spawn in the spring, when high stream flows elevate concentrations of toxic Al and decrease stream pH in acid-sensitive watersheds. We hypothesized that acidic episodes in spring were a source of stress for slimy sculpin and hindered their reproduction. We tested this hypothesis by examining the mortality, behavior, whole-body sodium concentrations, and spawning among slimy sculpin exposed to ambient conditions during the spring spawning period in two Pennsylvania streams, Stone Run (an episodically acidified stream that formerly contained slimy sculpin) and Benner Run (a stream with slimy sculpin that does not experience severe acidic episodes). Our hypothesis was supported by the higher mortality, hypoactivity, lower body sodium concentrations, and lack of spawning among slimy sculpin in Stone Run relative to those in Benner Run. Reproductive disturbance caused by stressful concentrations of Al and hydrogen ions may have led to the recruitment failure and collapse of the slimy sculpin population in Stone Run.

Notes

¹ Runoff events on April 20 and May 8, 1998, resulted in damage to the Benner Run cage and the escape of 5 fish.