The 1963 Chesapeake Bay Fish Mortalities with Notes on Other 1963 Chesapeake Bay Mortalities (Notes on 1964 Fish Kills are Also Included)

The literature, minutes of conference, data reports and other records, pertaining to the 1963 Chesapeake Bay fish kills has been reviewed in detail. Data concerning the few 1964 fish kills in Virginia waters are also appended. The various theories concerning the cause(s) of the kills have been carefully examined. All evidence indicates that the fishes killed, died as a result of interaction between unfavorable environmental factors and, in most species, bacterial disease (protozoan disease in 1964). Among the likely environmental stresses involved were: 1) severe hydroclimate, rapidly changing temperatures, high salinities due to drought, 2) low and high oxygens, 3) algal competition and 4) perhaps, population pressures induced by too many fishes per unit volume of water ( 11salinity compression11 in \·1hite perch). These stresses probably affected the fishes adversely in a direct fashion and in addition allowed or caused normally non-pathogenic or low-level pathogenic bacteria and/or protozoans present in the fishes to become pathogenic and cause the mass mortalities (or add to the severity of the mortalities)