**5. Downstream fishes and fisheries (Egyptian freshwater fisheries)**

Egypt is the downstream country hosting the last 1530 km of the Nile river channel. The Nile enters Egypt through the Nubian Lake which continues as Lake Nasser behind the Aswan High Dam (AHD). The water allowed to pass through the AHD is the Egyptian quota of Nile water (55.5 Km3 year -1) as outlined in an agreement with Sudan in 1959. This quantity satisfies the freshwater demands of the Egyptian population for use in agricultural irrigation, industry, domestic and navigation purposes. On the way to its Mediterranean destination, the Nile water fills many canals within the irrigation network in the western desert and the Nile delta. It also contributes to the water budget of the Northern Delta lakes [2]. Thus the freshwater inland water fisheries in Egypt include Lake Nasser (the second largest man made reservoir in Africa, after Lake Volta-Ghana), the Nile main river channel, irrigation channels, some water bodies in the Western Desert, the Nile branches (Rosetta and Damietta), and the Northern Delta Lakes (Manzala, Burullus, Idko and Mariut). The excess water is then discharged into the Mediter‐ ranean Sea through the lake connections with the sea via direct and indirect inlet openings [2]

The annual fish yield from freshwater fisheries of the Egyptian Nile basin has increased annually from 157,888 metric tons in 1990 to 224,940 metric tons in 2000 [14]. The catch increased for a number of reasons, such as the nutritive effect of sewage and fertilizer discharge in drainage channels and lakes, the intensified fishing activities and adjustment of incensement statistical techniques. Apart from the intensive aquaculture that has developed during the last twenty years in Egypt, the major contributors to the freshwater fish catch could be listed as Lake Nasser, Nile branches and irrigation channels as well as the northern Delta lakes. Their contribution may be summarized as follows:

#### **5.1. Lake Nasser fishes and Fisheries**

potential of the various fisheries (Table 2), as in some areas civil war disturbances and dense cover of aquatic macrophytes, and inadequate fishing gear have had a negative effect on local

**Actual Yields**

**Tons year-1 Percentages of Exploitations**

.

**Fish Catch Potential Tons year-1**

Sudd Region 75,000 30,00 43% White Nile Reservoir 15,000 13,000 86% Blue Nile Reservoir 1,700 1,500 88% Senner Reservoir 1,100 1,100 91% Lake Nubia Portion 5,100 1,000 19.6% Others 4,000 4,000 100% Total 101,900 50,500 ≈ 50%

**Table 2.** Calculated Potential and Effective Fish Catch from Different Inland Water Bodies of Sudan

are many other species, though they have no commercial value [13].

The predominant fishing gear includes active and passive gill nets, seine nets, trammel nets, long line hooks, cast nets and baskets. The commercially important fish are Nile perch (*Lates niloticus),* Bagrid catfish *(Bagrus bayad),* Silver catfish *(Bagruc docmac),* Nile tilapia *(Oreochromus niloticus),* Carp fish *(Labeo* spp.*),* Barbs fish *(Barbus binny),* Mormyrus fish *(Mormyrus* spp*.),* Nile Distichodus *(Distichodus* spp*.),* Tiger fish *(Hydrocyon* spp.*)* and Nile robber *(Alestes* spp*.).* There

It is important to state that, apart from the FAO reports, there is almost no scientific literature available on the ecological features and dynamics of fish populations in the inland waters of Sudan. This underlines the importance of organizing a research program on inland fisheries in this area in order to fill the gap of knowledge about the fisheries status in this important part of the Nile basin. This is especially important for the wet lands which are not limited to Sudan but also exist in the ten countries of the Nile basin, and account for an area of almost 200,000 km2

A characteristic of wetlands fisheries is the variety of traps that are used to catch fish in dominantly submerged or emergent vegetation habitats. Many of these traps have traditional designs adapted to local conditions and most are made from local plant materials - often from wetlands themselves. One type of fish requiring a special fishing technique is the African lungfish(*Protopterusaethiopicus*),whichisnativetoEthiopianwetlandsandinhabitstheseasonal

wetlands where it aestivates in the dried soil and is "hunted" during the dry season.

**5. Downstream fishes and fisheries (Egyptian freshwater fisheries)**

Egypt is the downstream country hosting the last 1530 km of the Nile river channel. The Nile enters Egypt through the Nubian Lake which continues as Lake Nasser behind the Aswan High Dam (AHD). The water allowed to pass through the AHD is the Egyptian quota of Nile

fish production.

356 Biodiversity - The Dynamic Balance of the Planet

**Area**

Lake Nasser lies behind the AHD and its extension in the northern Sudan is referred to as the Nubia reservoir. This lake has a depth reaching 180m and covers an area of 6216 km2 , 5248 km2 of which are in Egypt and the rest in Sudan (Fig. 1). The total fish catch from Lake Nasser has been estimated as 28,153 tons year -1 [15]. Tilapia species, mainly the Nile tilapia represent 90% of the total fish catch, while Nile perch and *Barbus* spp. cover the remaining 10%. Despite the large area of the lake, it contributes only about 10% of the total freshwater fish landing in the Egyptian Nile basin. This is probably due to its deep waters and the low number of motorboats with suitable fishing gear adapted to its bathymetry.

#### **5.2. Nile branches and irrigation channels fishes and fisheries**

There are more than 100 sites recorded along the Nile branches and major irrigation channels at which freshwater fishes are collected for marketing. Most fishermen in these areas are not registered. The fishing fleets at these sites comprise hundreds of small wooden boats (4-6 m in length). The fishing gear used is mostly primitive, though trammel nets are in use in some areas. The common fish species caught from these channels are tilapia species (*O. niloticus, O. aureus, Sarotherodon galilaeus* and *Tilapia zilli*) as well as *Clarias* spp.

Although these fishing sites are sparsely distributed and reliable statistics are in short supply, it has been estimated that 34% of the total Egyptian freshwater fish catch is slated to the two main Nile branches (Rosetta and Damietta) and the major irrigation channels [16].

### **5.3. Northern Delta lakes (NDL)**

As the final reservoirs of Nile river water before it flows into the Mediterranean, the four lakes (Mariut, Edku, Burullus and Manzalah) are the last opportunity for Egyptians to use the Nile water within the Delta area (Fig. 5). The four lakes occupy an area of about 1100 km². They are commonly shallow (average depth 1.10m), and their water salinity is known to change from fresh to brackish in the seaward direction. They are connected to the Mediterranean Sea either directly or indirectly.

**Year's L. Mariut Edku L. L. Burullus L. Mazalah** 1950's 136.9 150.1 571.8 1274.2 1970's 68.4 129.2 534.4 997.3 1980's 66.1 115.3 481.6 904.1 1990's 62.3 109.7 350.8 650.3

The Nile Fishes and Fisheries http://dx.doi.org/10.5772/57381 359

**Table 3.** Gradual changes in the surface areas (Km²), of the Northern Delta Lakes during the last 50 years "After, [17]"

According to the year 2001 records, the lakes fisheries had a total fish production of about 140,000 tons year -1, which represented about 60% of the freshwater fish catch and about 30% of the total annual yield of Egypt [16]. The main freshwater fish species living in the NDL are Nile tilapia (*Oreochromis niloticus),* Blue tilapia *(O. aureus), Mango tilapia (Sartherodon gali‐ laeus)* and *Tilapia zilli* also known as *Tilapia melanopleura,* Nile perch *(Lates niloticus),* Bagrid catfish *(Bagrus bayad),* Nile carp *(Labeo niloticus),* Yellow fish *(Barbus prince),* Barbus fish *(B. bynni bynni), and* African catfish *(Calrias gariepinus).* Other species, such as Grey mullet *(Mugil cephalus),*Thinlip grey mullet *(Liza ramada),* Saline mullet *(Liza salinus) and Eel fish Anguilla anguilla,* belonging to the brackish-marine sectors of the lakes, represent a minor part of the total catch of these lakes. The fishing fleets and gear used in the lakes are generally primitive and they are adapted to the shallow water depth and the presence of abundant emergent and submerged macrophytes. Thus wooden boats varying in size from 4 to >20 m in length and a

**6. Water quality in Major Nile basin fisheries and its impact on fish**

Studies of water quality of the Nile basin and its channels and lakes have demonstrated a trend of lower water quality in the downstream basins compared with those located upstream. This

The all-year round continuous flow of the river from south to north which dilutes existing

Neither water multi-use nor recycling processes are common practice in upstream countries

Low population densities and less modernized sewage systems at upstream countries

In addition to the above, the main impact of human activities in the areas surrounding the upstream Nile river water bodies may result from the uncontrolled drainage and discharge of

Less industrialization of upstream countries compared to the downstream ones.

number of net types and sizes are used.

**6.1. Water quality in the upstream basins**

pollutants and contaminants and carries them downstream.

is mainly due to the following:

compared with the downstream ones.

compared with the downstream ones.

**production**

**Figure 5.** The Northern Nile Delta lakes

During the last 50 years, the surface area of the four lakes has been reduced to as little as 50% of the area they covered during the 1950's (Table 3). The lake areas lost have been used for highway construction, reclamation of new lands for agriculture, and in some cases, for residential constructions. Such unnatural use of the lake basins has certainly modified their ecosystems as a whole, beginning with hydrological changes and resulting in the reduction of their economic and natural value. Due to their location along the coastal area of the Egyptian Mediterranean, the lakes are surrounded by or included within the highly populated coastal cities of the country. This has become more pronounced, particularly during the last 20 years, in the various forms of human impact on these water bodies, such as industrialization and the construction of new infrastructures in response to population density increases. These impacts are manifested in the deterioration of the water quality and reduction in lake surface area [17]. The consequent negative effect of human impact on the NDL ecosystems became evident in the decline in fish production. Up to 1985 the annual fish production of these lakes accounted for >50% of the total annual yield for the country.


**Table 3.** Gradual changes in the surface areas (Km²), of the Northern Delta Lakes during the last 50 years "After, [17]"

According to the year 2001 records, the lakes fisheries had a total fish production of about 140,000 tons year -1, which represented about 60% of the freshwater fish catch and about 30% of the total annual yield of Egypt [16]. The main freshwater fish species living in the NDL are Nile tilapia (*Oreochromis niloticus),* Blue tilapia *(O. aureus), Mango tilapia (Sartherodon gali‐ laeus)* and *Tilapia zilli* also known as *Tilapia melanopleura,* Nile perch *(Lates niloticus),* Bagrid catfish *(Bagrus bayad),* Nile carp *(Labeo niloticus),* Yellow fish *(Barbus prince),* Barbus fish *(B. bynni bynni), and* African catfish *(Calrias gariepinus).* Other species, such as Grey mullet *(Mugil cephalus),*Thinlip grey mullet *(Liza ramada),* Saline mullet *(Liza salinus) and Eel fish Anguilla anguilla,* belonging to the brackish-marine sectors of the lakes, represent a minor part of the total catch of these lakes. The fishing fleets and gear used in the lakes are generally primitive and they are adapted to the shallow water depth and the presence of abundant emergent and submerged macrophytes. Thus wooden boats varying in size from 4 to >20 m in length and a number of net types and sizes are used.
