Annually exploited communities from the Nile delta and two nearby lagoons (Manzalah and Edkou) were monitored from 1962 to 1989. The changes in community structure were analysed as a function of two events: fishing pressure growth (motorized fishing vessels) which increased by a factor of 19 between 1952 and 1962; and the construction of the Aswan Dam, which was built between 1965 and 1969, reducing the flow of the Nile by 90 %. Before the construction of the dam, increased sea fishing pressure led to a decline in landings from 33,832 tons in 1962 to 8,522 tons in 1969, but with no structural change in the exploited community. However, following completion of the dam in 1969, the community structure changed and a significant correlation was detected between landings and community diversity. After 1978, a period of variability in landings and the simultaneous reorganization of the communities occurred. By 1989, fish landings reached 32,025 tons, a level recorded before the construction of the Aswan dam In contrast With the previous period, there Was no longer a significant correlation between community structure and catches. Quantitative variations were observed in Manzalah Lagoon landings but with no modification in community structure. Con-elation between diversity and catches was found only in the Edkou Lagoon.