ASSESSING THE RELATIONSHIP BETWEEN CRITICAL ACIDIC CONDITIONS IN MARYLAND COASTAL-PLAIN STREAMS AND PREDICTED MORTALITY OF EARLY-LIFE STAGES OF MIGRATORY FISH

This study was designed to assess the relationship between critical ac idic conditions (pH, monomeric aluminum) in Maryland coastal plain str eams and predicted mortality of early life stages of migratory fish su ch at yellow perch, white perch, blueback herring and alewife (focal s pecies). Physicochemical parameters were evaluated in three acid-sensi tive coastal plain streams in Maryland (Mattawoman Creek, Bacon Ridge Branch and Faulkner Branch) during rain events. Monitoring of focal sp ecies was conducted to determine whether potentially toxic acidificati on conditions from episodic acidic rain events occurred simultaneously with the presence of susceptible early life stages of the four migrat ory species. Critical acidic conditions for larval alewife were report ed in Mattawoman Creek concurrently when these life stages were presen t in the creek. Critical acidic conditions were also reported for blue back herring and alewife in Bacon Ridge Branch; however, populations o f these two species were not reported during our monitoring efforts. P opulations of yellow perch and white perch were also very low or absen t. The few yellow perch collected in Bacon Ridge Branch were likely a result of a stocking effort. Alewife, blueback herring and white perch ichthyoplankton were collected at Faulkner Branch; adults of all four focal species, except blueback herring, were also collected. Critical acidic conditions for blueback herring and alewife were reported for only two out of eight possible intervals in this stream. Episodic acid ification events in Maryland coastal plain streams are stressful to al ewife and blueback herring and are inhibiting recovery of these deplet ed stocks.