Acidic Groundwater Discharge and in Situ Egg Survival in Redds of Lake‐Spawning Brook Trout

Abstract

AbstractSpawning of brook trout Salvelinus fontinalis in lakes occurs over areas of groundwater discharge. The rate and chemistry of groundwater discharge influence brook trout egg survival and reproductive success. While most studies have reported that groundwater discharge in brook trout redds is buffered relative to the surrounding lake water, we documented brook trout spawning over an area of acidic groundwater discharge (pH as low as 4.7) in a lake with circumneutral surface waters (pH > 6.1). A follow‐up experiment that assessed in situ egg survival indicated 0% survival in redds with either low‐pH groundwater or adequate groundwater pH but low groundwater discharge. More than 80% of eggs survived in a reference lake with well‐buffered groundwater and adequate discharge rates. These results suggest that both low pH and low groundwater flow rates may contribute to brook trout egg mortality. Low‐pH groundwater may be a factor to consider in brook trout restoration efforts, especially in lakes where whole‐lake liming has been unsuccessful in reestablishing wild brook trout populations.