The production of Liza ramada (Risso) in Lake Mariul. Egypt 251 



egg from a population introduced into Lake Quarun (Wivipfsw. 1936), none has 

 been found in the water of the coastal belt either near Lake Mariut or anywhere else 

 in the world, and the location of the actual spawning grounds, bearing the number of 

 eggs that must necessarily be present to account for the origin of the huge runs of young 

 fish into fresh water, remains a mystery. 



There is, therefore, a gap in our knowledge of the life cycle of this species between 

 the departure of the spawning shoals and the arrival of swarms of small scaled 

 individuals in the out-flowing fresh water at the beginning of January. 



Lake Mariut during the period to which this account refers was an area of approxi- 

 mately 59,000 acres of water rarely more than 50 cm deep and situated behind the 

 town of Alexandria. The Department of Irrigation maintained it around a level of 

 3 metres below sea-level (rather above this in the early part of the period, rather below- 

 later), and it acted as a drainage reservoir for the farm lands of the north-west part 

 of the Nile delta. The drain water reaches the lake chiefly through a large channel 

 called the Omoom drain. A channel at sea-level runs from the sea to the lake-side at 

 a place called Mex. Here powerful pumps force the water from a canal on the lake- 

 side up into the sea canal. It was usual for these pumps to work from August to April, 

 as during the rest of the year the evaporative power of the sun, estimated to have been 

 750,000 to 1,000,000 tons per day, was considered sufficient to keep the lake at the 

 required level. 



The eff'ect of these arrangements was that there was no contact between sea and 

 lake when the pumps were not working, but for the rest of the time the water flowed 

 with considerable velocity from the lake to the sea. The sea water never flowed into, 

 nor was it on a level with the lake; thus the penetration of marine animals was 

 obstructed. In these circumstances spawning shoals of Tobar found it easy to leave 

 the lake in the spawning season, but the fry, attracted to the outflow of fresh water 

 in the Mex channel, were prevented from passing in through the pumps, and gathered 

 against the walls of the channel with their heads facing upstream as near the pumps 

 as possible. There they collected in great numbers, and until 1920 this obstacle to 

 their progress stopped other than stray individual Tobar, that had wandered into the 

 lake by the inland drains, from populating the lake. 



In 1920 the Director of Fisheries Research of that day, Mr. Paget, organized a 

 service of transplantation which consisted in sweeping up the fry from alongside the 

 walls of the marine canal by long-handled nets having a mosquito netting bag and a 

 rectangular head. The fry thus caught were carried to the lake-side of the pumps in 

 buckets, and poured into boats with perforated zinc removable sides. When the boats 

 were sufficiently charged with fry, they were towed some distance out into the lake and 

 the fry released. The bags of the nets were marked so that a record of the number of 

 fry could be kept. This introduction, made at a cost of a few hundreds of pounds 

 annually, resulted in a fishery for two species of grey mullet running into tens o\' 



thousands each year. 



For the fifteen years 1920-35 there are available (Egypt, Government Press, 1922-26) 



(a) statistics concerning the weights and values of the different species of hsh 

 collected at the landing places on Lake Mariut; (b) the record of numbers ot try 

 introduced; (c) information on the number of fishing boats at work (from the 

 licensing system) and (d) particulars relating to the water level and supply (from the 

 Department of Irrigation). In addition to this, for the years 1928-31 and 1933, there 



