This lake is a typical delta edge lagoon lake with a history of steady contraction from 200 km2 before the 1940s to some 150 km2 in the 1950s to the present 70 km2 (Fisheries Department estimates). It is estimated that a reduction of some 30 percent of the lake area has occurred in the last 20 years by the development of drainage and irrigation schemes in the eastern portion. In addition to the losses to agricultural use, the changes brought about by increasingly intensive agriculture, lowered quantities of available water and greater economy in water use for irrigation, has lead to an acceleration in the growth of reeds (mostly Phragmites) and more recently the development of floating masses of water hyacinth (Eichhornia). The lake also supports considerable stands of sub-aquatic plants (Potamogeton), with these occupying a possible 50 percent of the apparently open water surface.
Typically this is a shallow, eutrophic lake at an advanced and accelerating stage of senescence, or evolution to dry land. Although it has not been possible to verify the area by reference to aerial photographs, overflights or records of recent surveys, observations suggest that the open waters of the lake cover some 70 km2, with an additional estimated 30 km2 of overgrown areas not accessible to the fishermen. The total of 100 km2 can be assumed to be the productive area for the assessment of possible available fishery resources. The lake occupies a very shallow basin with little variation in a depth of between 0.5 and 1.0 m. Encroachment of reeds and deposition of silt reduce the margins to shallow marshes, which allow reclamation and encroachment by agriculture, particularly in the south. To the north the lake boundary is fixed by the coast road and railway line which follow the line of the coastal sand dunes. There is some encroachment of the lake margins on this northern edge. In the east the lake edge is defined by the Edku Drain carrying irrigation drainage raised from the neighbouring agriculture areas. Apart from the Edku Drain, the Barsik Drain enters from the middle of the southern shore and the Bersila Drain enters in the northeast corner. The lake drains to the Mediterranean Sea through a single narrow channel at the sea fishing port of Maadia. It is understood that occasionally this drainage reverses with the inflow of sea water into the lake. There is evidence of this from the response of the vegetation in the vicinity of Maadia and the area of the lake to the west. The drainage of agricultural, irrigated land into the lake provides a nutrient-rich input with a salinity of about 2–3 ppt over much of the lake surface.
The water is not homogenous in appearance, varying from clear to at least the maximum 1.0 m depth, to very cloudy with sediment/plankton and in some areas foul anoxic water smelling of hydrogen sulphide. Such patchiness in the water mass would be expected due to the low flows and the localized effect of water passing through, or being blocked by, stands of submerged plants or where reversal of current flow, through tidal or wind effects, causes water to be flushed out from below consolidated stands of water hyacinth. There is apparently no significant input of organic or industrial pollutants to the lake, apart from the enhanced nutrient status of the discharged drainage waters and the residual load of pesticides they carry. There is however a considerable input of herbicides (currently Ametryn) in the October of each year for the last 10 years as a part of a programme to eradicate or reduce the water hyacinth. It is not known what effect these chemicals and their resides will have on the fish or the edible quality of the fish flesh. It appears that there is no monitoring programme for pesticide residues in the waters of the area or edible products derived from them.
The lake is exposed to the prevailing winds with a reach over the sea or the flat agricultural lands of the delta. With its shallow depth and relatively large area, it is unlikely that there will be any significant stagnation or stratification. The exception to this will be those areas which are blocked by floating and emergent weeds. These are localized and any deterioration in water quality would provide little risk to the fish populations.
Discrete waterbodies are observable within the lake by colouring and clarity, but their overall pattern could not be ascertained. The major significant heterogenity is the area to the west of the connection with the sea at Maadia. The lack of aquatic vegetation over a considerable area suggests that this part of the waterbody is subject to considerable fluctuations in salinity, with presumably the salinity changing with the reversal of flow through the lake-sea junction.
Construction of the Barsik Fish Farm began in 1979. Table 1 provides a summary of the recent history of the station.
The farm was constructed on a 800 ha site in the southeast sector of Lake Edku, to designs elaborated by the Irrigation Department. Before construction began the site was a mixture of areas of Phragmites reed swamp in the north and west and a drier salt marsh scrub in the south and east of the site.
The farm consists of approximately 685 ha of water surface, with 625 ha consisting of 104 production ponds of about 6 ha each with a water depth of 1 –1.5 m. In the southwest corner of the site are a further series of 50 smaller (+ 1 ha) ponds for breeding and raising broodstock. The farm does not include a hatchery, but relies on Government hatcheries at some 30 km distance for fish for stocking.
| Date | Event |
| 1979 (September) | Construction started |
| 1982 (September) | First stocking of 600 feddan (240 ha) |
| 1983 (September) | First harvesting of 600 feddan (240 ha) with a yield of 250 kg/feddan (625 kg/ha) |
| 1984 (October) | Second harvest * of 1 470 feddan (600 ha) with a yield of 400 kg/feddan (1 000 kg/ha) |
| 1985 (October) | Anticipated third harvest * from 1 560 feddan (625 ha) or maximum stocked area |
* Production period approximately 6 months
The water supply is obtained from a land drainage canal and pumped via a pump house supplied with 5 × 75 hp electric pumps with a total capacity of 5 000 m3/h. A second pump house of the same design and capacity drains the whole pond area to the Barsik Drain and eventual discharge to Lake Edku. All the ponds are independently filled and drained via large canals. The inflow of water through the sluices into many of the larger ponds is restricted by the small diameter of the inflow pipes (+ 0.2 m).
The farm possesses labour lines, administrative, maintenance and storage buildings, all situated on a site in the southwest corner.
Although only some 5 years old there is already a considerable backlog of maintenance and replacement work, in particular many of the buildings, including the pump houses, equipment such as fish screens, etc. Bund-top roads are at risk to erosion. The ponds are rectangular, 1.0–1.5 m deep, each provided with independent inflow and drainage sluices. A fish sump is dug around the edge of the production ponds. Most bunds are accessible by vehicle. The current condition of the ponds reflects both the nature of the site and pond construction as well as subsequent pond management.
The soil type of the site divides by an approximate NE to SW diagonal. The eastern portion was constructed on what was apparently salt marsh and demonstrates a low level of reed growth. The western area was constructed on a reed swamp and these ponds now support massive stands of reeds.
Some of the ponds of the extreme NW end of the pond complex have been badly surveyed and under-excavated. Consequently their depth in some cases is less than 30 cm with pond bottoms breaking the surface. These ponds should not be put into production until this situation is rectified.
Where ponds have been cleared and well managed, the weed nuisance is minimal.
