THE BIOLOGY AND FISHERY OF MUGEL SALIENS

1. -INTRODUCTION
Lake Quarun is in the lowest part of the Fayoum depression located in the
Western Desert, 83 kilometers S.S.W. of Cairo (Fig. 1). This lake has an area
of about 53,000 acres and a maximum depth of 8 m. However, most of the lake
is less than 6 m.
Lake Quarun represents the remnant of Lake Moeris and has undergone
pronounced ecological changes which affected its fauna and flora. In ancient
times, when this lake was used as a resrvoir for the Nile flood it was probably
inhabited by most of the species of Nile :fishes (Faouzi, 1936). Since it became
a drainage reservoir for the Fayoum irrigation system, the amount of fresh water
which reaches it from the Nile has been greatly reduced. It now receives only
brackish drainage water (Gorgy, 1959). The salinity has changed as follows :
n. 6 p.p.m. in 1920, 17.19 p.p.m in 1930,22.4 p.p.m in 1932 and 23.4 p.p.m
in 1934. At present the salinity varies between 17.45 p.p.m and 29.43 according
to the distance from the drainage canals. The average air temperature at
2 p.m. varied from 17.6 Coin January to 31. 9°C in August. The rate of evaporation for the year of 1950 ranged from 11.6 mm in December to 282.9 nun
in June and the total evaporation for that year was 1,873.3 mm (Gorgy, 1959).