THE EFFICACY OF A LIMESTONE DOSER TO MITIGATE STREAM ACIDIFICATION INA MARYLAND COASTAL-PLAIN STREAM - IMPLICATIONS FOR MIGRATORY FISH SPECIES

The objective of this two-year study was to determine the efficacy of an automated limestone slurry doser to neutralize acidic pulses and im prove water quality conditions for enhancing survival of early life st ages of migratory fish species in a Maryland coastal plain stream. Imp lications for survival of early life stages of migratory fish species such as yellow perch (Perca flavescens), white perch (Morone americana ), blueback herring (Alosa aestivalis) and alewife (Alosa pseudohareng us) are discussed based on the improved chemical conditions in the dos ed area of the stream. Despite problems with overdosing in 1991 and fa ilure of the stage transducer to work properly in 1992, the doser was generally effective in neutralizing acidic pulses (pH depressions) in the stream during three major rain events in both years. Chemical cond itions (pH and inorganic monomeric aluminum) reported in the non-dosed area during major rainfall events were potentially stressful to both alewife and blueback herring although neither species was reported spa wning in the stream during either year. Mitigating the potential impac t of acidic conditions on early life stages of important migratory fis h species was not sufficient to ensure spawning. It is therefore recom mended that habitat improvement measures and well designed fish stocki ng programs be implemented concurrently with doser operations if the g oal is to create optimum spawning conditions for migratory species.