**3. Fish and fisheries of tropical lakes (L. Victoria and L. Tana)**

Fishes and fisheries of Lake Victoria and Lake Tana will be reported here, as natural examples of tropical large water bodies of the Nile basin. The combined surface area of these lakes is


quantity of fish landed in Lake Victoria fisheries reaching a total of 500,000 tons per year. This figure was in decline by the late 1990's and early 2000's when it reached a total of 340,000 ton per year (Fig. 2). This reduction was mainly due to the overexploitation of the fisheries resources, and to the increase in the number of motorized boats, and to the Nile perch processing industries. Reportedly the number of fishing boats in the lake increased from 12,000 boats during 1982 to 22,700 boats during 1990 and more than 52,000 boats in 2002 [6]. In recent years, as fishing pressure on the Nile perch has intensified, there are signs of recovery in at least some of the former haplochromine species that were thought to be extinct from the lake

**Total Fish Landing of Lake Victoria during the period 1977-2002**

1992

**Figure 2.** Variation of the total fish landing of Lake Victoria during the period 1977-2002 [8]

the ratios 3.75, 3.0 and 1.75 for the three fishes, respectively.

2000

**Year**

Extracted data from the results obtained by [6], from the ECOPATH prediction model have revealed that the stock biomass (tons km-2) of the fishes (Nile perch, tilapia and sardine) are different in the waters of Lake Victoria shared by different countries. The same is also true for the ratios of production per biomass except for the sardine species (Fig. 3). The data also shows that the Ugandan lake areas have lowest stock of Nile perch biomass, while the highest stocks are found in the Kenyan lake areas. Interestingly, the Ugandan stock biomass of tilapia is the highest while the Tanzanian stocks are the lowest. The sardine stock biomass is higher in the Kenyan lake areas followed by the Tanzanian, with the lowest recorded in the Ugandan lake areas (Fig. 3). An overall estimate shows that the average stock biomass for the whole of Lake Victoria is 4.59 tons km-2 for the Nile perch, 3.27 tons km-2 for the sardine and 2.36 tons km-2 for the tilapia. The same trend is observed for the estimate of production/biomass year-1, giving

2002

The Nile Fishes and Fisheries http://dx.doi.org/10.5772/57381 353

environment [9], [10], [5].

0

1977

Kenya Uganda Tanzania

50,000

100,000

150,000

**Tons/year**

200,000

250,000

**Table 1.** National areas within the Nile Basin "Source [14]"

75% of the total of the five tropical lakes of the Nile basin. They are also important because they lie at the source of both the White Nile and the Blue Nile, respectively. Their main fishes are representative of the fish species living in the other lakes (Edward, Albert and Kyoga). Details on the other tropical lakes (Edward, Albert, Kyoga, and George) fish fauna and its fisheries are found elsewhere [4], [5].

#### **3.1. Lake Victoria (Kenya, Tanzania and Uganda)**

Lake Victoria is the largest natural lake in Africa (Fig. 1) and the second largest lake in the world after Lake Superior (USA-Canada). It has a surface area of 68,800 km2 and a very large catchment area of 193,000 km2 . The shoreline measures 3450 km in length and the lake has a mean depth of 40 m and a maximum depth of 80 m. The lake is shared by Kenya (6%), Uganda (43%), and Tanzania (51%). The lake basin is estimated to have a population of 30 million individuals which is growing at a rate of >3% per annum. Three major cities (Kampala, Kisumu and Mwanza) with a combined population of about six million inhabitants depend on the lake for domestic and municipal water supply and waste disposal. Recent data has shown it is becoming eutrophic [6].

Two introduced species, Nile perch (*Lates niloticus*) and Nile tilapia (*Oreochromus niloticus*), and one native cyprinid (*Rastrineobola argentea*) dominate the lake's fisheries. The introduction of the Nile perch (*L. niloticus*), in the early 1960's had major ecological consequences. It is believed that some 200 endemic halochromine species (previously comprising 90% of the lake fish biomass) have become extinct in the lake due to predation by the Nile perch [7]. Most of these species had no commercial value, but are now considered relevant to the sustainability of the Lake Victoria ecosystem [8]. Lake Victoria fisheries production has increased markedly since the introduction of the Nile perch. Despite the general unreliability of published data, there is agreement that between the late 1980's and early 1990's there was an increase in the quantity of fish landed in Lake Victoria fisheries reaching a total of 500,000 tons per year. This figure was in decline by the late 1990's and early 2000's when it reached a total of 340,000 ton per year (Fig. 2). This reduction was mainly due to the overexploitation of the fisheries resources, and to the increase in the number of motorized boats, and to the Nile perch processing industries. Reportedly the number of fishing boats in the lake increased from 12,000 boats during 1982 to 22,700 boats during 1990 and more than 52,000 boats in 2002 [6]. In recent years, as fishing pressure on the Nile perch has intensified, there are signs of recovery in at least some of the former haplochromine species that were thought to be extinct from the lake environment [9], [10], [5].

**Figure 2.** Variation of the total fish landing of Lake Victoria during the period 1977-2002 [8]

75% of the total of the five tropical lakes of the Nile basin. They are also important because they lie at the source of both the White Nile and the Blue Nile, respectively. Their main fishes are representative of the fish species living in the other lakes (Edward, Albert and Kyoga). Details on the other tropical lakes (Edward, Albert, Kyoga, and George) fish fauna and its

**Country Area in basin (km3) Percentage of total country area in**

Burundi 13 000 46% D R Congo 22 300 1% Eritrea 25 700 21% Ethiopia 366 000 32% Egypt 307 900 33% Kenya 52 100 9% Rwanda 20 400 83% Sudan 1943 100 78% Tanzania 118 400 13% Uganda 238 700 98%

Lake Victoria is the largest natural lake in Africa (Fig. 1) and the second largest lake in the

mean depth of 40 m and a maximum depth of 80 m. The lake is shared by Kenya (6%), Uganda (43%), and Tanzania (51%). The lake basin is estimated to have a population of 30 million individuals which is growing at a rate of >3% per annum. Three major cities (Kampala, Kisumu and Mwanza) with a combined population of about six million inhabitants depend on the lake for domestic and municipal water supply and waste disposal. Recent data has shown it is

Two introduced species, Nile perch (*Lates niloticus*) and Nile tilapia (*Oreochromus niloticus*), and one native cyprinid (*Rastrineobola argentea*) dominate the lake's fisheries. The introduction of the Nile perch (*L. niloticus*), in the early 1960's had major ecological consequences. It is believed that some 200 endemic halochromine species (previously comprising 90% of the lake fish biomass) have become extinct in the lake due to predation by the Nile perch [7]. Most of these species had no commercial value, but are now considered relevant to the sustainability of the Lake Victoria ecosystem [8]. Lake Victoria fisheries production has increased markedly since the introduction of the Nile perch. Despite the general unreliability of published data, there is agreement that between the late 1980's and early 1990's there was an increase in the

. The shoreline measures 3450 km in length and the lake has a

and a very large

**Nile Basin**

world after Lake Superior (USA-Canada). It has a surface area of 68,800 km2

fisheries are found elsewhere [4], [5].

352 Biodiversity - The Dynamic Balance of the Planet

catchment area of 193,000 km2

becoming eutrophic [6].

**3.1. Lake Victoria (Kenya, Tanzania and Uganda)**

**Table 1.** National areas within the Nile Basin "Source [14]"

Extracted data from the results obtained by [6], from the ECOPATH prediction model have revealed that the stock biomass (tons km-2) of the fishes (Nile perch, tilapia and sardine) are different in the waters of Lake Victoria shared by different countries. The same is also true for the ratios of production per biomass except for the sardine species (Fig. 3). The data also shows that the Ugandan lake areas have lowest stock of Nile perch biomass, while the highest stocks are found in the Kenyan lake areas. Interestingly, the Ugandan stock biomass of tilapia is the highest while the Tanzanian stocks are the lowest. The sardine stock biomass is higher in the Kenyan lake areas followed by the Tanzanian, with the lowest recorded in the Ugandan lake areas (Fig. 3). An overall estimate shows that the average stock biomass for the whole of Lake Victoria is 4.59 tons km-2 for the Nile perch, 3.27 tons km-2 for the sardine and 2.36 tons km-2 for the tilapia. The same trend is observed for the estimate of production/biomass year-1, giving the ratios 3.75, 3.0 and 1.75 for the three fishes, respectively.

In 1992-1993 about 113 reed boats were counted on the lake and about 374 gill nets were in use, with an overall daily haul averaging 12.3 kg (7.8 kg Nile tilapia, 4.3 kg *Labeobarbus* spp. and 0.2 kg African catfish). Here it is important to indicate that *Labeobarbus* spp. in this lake is represented by nearly 15 species. It was also reported at that time that the fishermen in the lake numbered about 400 individuals. This meant that each reed boat had only one fisherman [12]. The introduction of motorboats to Lake Tana fisheries was a consequence of the increasing demand for fish from the capital Addis Ababa. This introduced an additional 130 professional fishermen, which markedly negatively influenced the fish stock in the lake. In fact, the annual total catch fell to 255 metric tons in 2001 from a value of 360 metric tons in 1997. Not only was there a reduction in total catch but also the percentage composition of the individual fish species yield varied between 1993 and 2001, so that the catch of *Labeobarbus* spp. declined by almost third in 2001 compared to 1993. Notably, the catch of Nile tilapia increased 50% in 2001 compared to 1993 (Fig. 4). This may reflect the intensive exploitation of *Labeobarbus* spp. and

by nearly 15 species. It was also reported at that time that the fishermen in the lake numbered about 400 individuals. This meant that each reed boat had only one fisherman [12]. The introduction of motorboats to Lake Tana fisheries was a consequence of the increasing demand for fish from the capital Addis Ababa. This introduced an additional 130 professional fishermen, which markedly negatively influenced the fish stock in the lake. In fact, the annual total catch fell to 255 metric tons in 2001 from a value of 360 metric tons in 1997. Not only was there a reduction in total catch but also the percentage composition of the individual fish species yield varied between 1993 and 2001, so that the catch of Labeobarbus spp. declined by almost third in 2001 compared to 1993. Notably, the catch of Nile tilapia increased 50% in 2001 compared to 1993 (Fig. 4). This may reflect the intensive exploitation of Labeobarbus spp. and the superior ability of the Nile tilapia to multiply in the lake.

50

during periods of high water level. The inland fisheries of Sudan are

during periods of high water level. The inland fisheries of

70

Labeobarbus spp O. niloticus C.garipinus

The Nile Fishes and Fisheries http://dx.doi.org/10.5772/57381 355

), its inland water

), its inland water

<sup>145</sup> <sup>140</sup>

1993 2001 Year

Figure 4. Total catch of the three main species from Lake Tana during the years 1993 and 2001 [13]

Although Sudan is a country with a very large surface area (2,505,825 km<sup>2</sup>

Although Sudan is a country with a very large surface area (2,505,825 km2

**Figure 4.** Total catch of the three main species from Lake Tana during the years 1993 and 2001 [13]

based on the Nile river tributaries, contributing over 90% of the estimated production potential of the country. The Sudd swamps in the south (Fig. 1), and the man-made lakes on the White Nile, the Blue Nile, Atbara river and the main Nile river (Lake Nasser portion in Sudan "Nubia") count as the major fishing localities with respect to fish resource magnitude and exploitation thrust [13]. The total fish production of the various inland water bodies and wetlands are estimated at 50,000 tons year -1. This figure is not representative of the full 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

**4. Fish and fisheries of Mid Nile (Sudan freshwater fish and fisheries)**

Sudan are based on the Nile river tributaries, contributing over 90% of the estimated produc‐ tion potential of the country. The Sudd swamps in the south (Fig. 1), and the man-made lakes on the White Nile, the Blue Nile, Atbara river and the main Nile river (Lake Nasser portion in Sudan "Nubia") count as the major fishing localities with respect to fish resource magnitude and exploitation thrust [13]. The total fish production of the various inland water bodies and wetlands are estimated at 50,000 tons year -1. This figure is not representative of the full

the superior ability of the Nile tilapia to multiply in the lake.

130

Tons/year

bodies occupy only 114,000 km<sup>2</sup>

bodies occupy only 114,000 km2

negative effect on local fish production.

90

4. Fish and fisheries of Mid Nile (Sudan freshwater fish and fisheries)

7

Figure 3, Biomass potentials of different water sectors of Lake Victoria for the main three fish species (tons km-2) [8] **Figure 3.** Biomass potentials of different water sectors of Lake Victoria for the main three fish species (tons km-2) [8]

 The artisanal fishing gear was in use on traditional fishing boats in Lake Victoria fisheries until the industrial exploitation of the Nile perch for international commercialization. At that time, motorized boats and improved fish gear "even illegal" was used. The most common gear used in Lake Victoria fisheries are gill nets and long-line hooks. During the period of 2000 and 2004, the numbers of gill nets in use increased by 50% reaching 980,000 gill nets, while the numbers of long-line hooks is estimated at 8 million in 2001. This number was adjusted to only 6 million during [6]. The current haul is estimated at 45 kg boat -1 day -1 compared with the 80 kg boat -1 day -1 figure during 1990's. This indicates over-intensive exploitation of the fisheries of Lake Victoria fish resources and argues for sustainable management intervention. 3.2. Lake Tana (Ethiopia) Lake Tana is the largest lake in Ethiopia (surface area 3,050 km<sup>2</sup> ). It lies at an altitude of approximately 1800 m ASL in the north-western highlands of Ethiopia, 500 km north of the capital The artisanal fishing gear was in use on traditional fishing boats in Lake Victoria fisheries until the industrial exploitation of the Nile perch for international commercialization. At that time, motorized boats and improved fish gear "even illegal" was used. The most common gear used in Lake Victoria fisheries are gill nets and long-line hooks. During the period of 2000 and 2004, the numbers of gill nets in use increased by 50% reaching 980,000 gill nets, while the numbers of long-line hooks is estimated at 8 million in 2001. This number was adjusted to only 6 million during 2006 [6]. The current haul is estimated at 45 kg boat -1 day -1 compared with the 80 kg boat -1 day -1 figure during 1990's. This indicates over-intensive exploitation of the fisheries of Lake Victoria fish resources and argues for sustainable management intervention.

Addis Ababa (Fig. 1). The lake is shallow (average depth 8 m, maximum depth 14 m), and its trophic

#### status is described as oligo-mesotrophic [11]. The lake's fishery is 30 km downstream from the Blue Nile outflows, and is isolated from the lower Nile basin by 40m high waterfalls. Physical and **3.2. Lake Tana** *(Ethiopia)*

hydrological features of the lake water follow a seasonal pattern. Rainfall peaks in July-August are followed by a rise in the lake water level by 1.5 m, reaching highest levels in September- October [12]. In their study, [12] identified the three endemic fish species groups Labeobarbus spp., Clarias gariepinus (African catfish), and Oriochromus niloticus (Nile tilapia), as the main representatives of Lake Tana fisheries. They noted that before 1986 Lake Tana was a subsistence fishery exploited predominantly by reed boat fishing vessels. This type of fishery was limited to the shore areas and targeted the native Nile tilapia using locally made fish traps and small gill nets. In 1992-1993 about 113 reed boats were counted on the lake and about 374 gill nets were in use, with an overall daily haul averaging 12.3 kg (7.8 kg Nile tilapia, 4.3 kg Labeobarbus spp. and 0.2 kg African catfish). Here it is important to indicate that Labeobarbus spp. in this lake is represented Lake Tana is the largest lake in Ethiopia (surface area 3,050 km2 ). It lies at an altitude of approximately 1800 m a.s.l. in the north-western highlands of Ethiopia, 500 km north of the capital Addis Ababa (Fig. 1). The lake is shallow (average depth 8 m, maximum depth 14 m), and its trophic status is described as oligo-mesotrophic [11]. The lake's fishery is 30 km downstream from the Blue Nile outflows, and is isolated from the lower Nile basin by 40m high waterfalls. Physical and hydrological features of the lake water follow a seasonal pattern. Rainfall peaks in July-August are followed by a rise in the lake water level by 1.5 m, reaching highest levels in September-October [12].

6 In their study, DeGraaf et al. [12] identified the three endemic fish species groups Barbs or yellow fish (*Labeobarbus* spp.*)*, African catfish (*Clarias gariepinus)*, and Nile tilapia *(Oriochromus niloticus)*, as the main representatives of Lake Tana fisheries. They noted that before 1986 Lake Tana was a subsistence fishery exploited predominantly by reed boat fishing vessels. This type of fishery was limited to the shore areas and targeted the native Nile tilapia using locally made fish traps and small gill nets.

In 1992-1993 about 113 reed boats were counted on the lake and about 374 gill nets were in use, with an overall daily haul averaging 12.3 kg (7.8 kg Nile tilapia, 4.3 kg *Labeobarbus* spp. and 0.2 kg African catfish). Here it is important to indicate that *Labeobarbus* spp. in this lake is represented by nearly 15 species. It was also reported at that time that the fishermen in the lake numbered about 400 individuals. This meant that each reed boat had only one fisherman [12]. The introduction of motorboats to Lake Tana fisheries was a consequence of the increasing demand for fish from the capital Addis Ababa. This introduced an additional 130 professional fishermen, which markedly negatively influenced the fish stock in the lake. In fact, the annual total catch fell to 255 metric tons in 2001 from a value of 360 metric tons in 1997. Not only was there a reduction in total catch but also the percentage composition of the individual fish species yield varied between 1993 and 2001, so that the catch of *Labeobarbus* spp. declined by almost third in 2001 compared to 1993. Notably, the catch of Nile tilapia increased 50% in 2001 compared to 1993 (Fig. 4). This may reflect the intensive exploitation of *Labeobarbus* spp. and the superior ability of the Nile tilapia to multiply in the lake. by nearly 15 species. It was also reported at that time that the fishermen in the lake numbered about 400 individuals. This meant that each reed boat had only one fisherman [12]. The introduction of motorboats to Lake Tana fisheries was a consequence of the increasing demand for fish from the capital Addis Ababa. This introduced an additional 130 professional fishermen, which markedly negatively influenced the fish stock in the lake. In fact, the annual total catch fell to 255 metric tons in 2001 from a value of 360 metric tons in 1997. Not only was there a reduction in total catch but also the percentage composition of the individual fish species yield varied between 1993 and 2001, so that the catch of Labeobarbus spp. declined by almost third in 2001 compared to 1993. Notably, the catch

of Nile tilapia increased 50% in 2001 compared to 1993 (Fig. 4). This may reflect the intensive exploitation of Labeobarbus spp. and the superior ability of the Nile tilapia to multiply in the lake.

Figure 4. Total catch of the three main species from Lake Tana during the years 1993 and 2001 [13] **Figure 4.** Total catch of the three main species from Lake Tana during the years 1993 and 2001 [13]

4. Fish and fisheries of Mid Nile (Sudan freshwater fish and fisheries)

7

6

fish traps and small gill nets.

[12].

**3.2. Lake Tana** *(Ethiopia)*

Lake Victoria

0.502

Lake Tana is the largest lake in Ethiopia (surface area 3,050 km<sup>2</sup>

Lake Tana is the largest lake in Ethiopia (surface area 3,050 km2

Lake Victoria fish resources and argues for sustainable management intervention.

approximately 1800 m ASL in the north-western highlands of Ethiopia, 500 km north of the capital Addis Ababa (Fig. 1). The lake is shallow (average depth 8 m, maximum depth 14 m), and its trophic status is described as oligo-mesotrophic [11]. The lake's fishery is 30 km downstream from the Blue Nile outflows, and is isolated from the lower Nile basin by 40m high waterfalls. Physical and hydrological features of the lake water follow a seasonal pattern. Rainfall peaks in July-August are followed by a rise in the lake water level by 1.5 m, reaching highest levels in September- October

In their study, [12] identified the three endemic fish species groups Labeobarbus spp., Clarias gariepinus (African catfish), and Oriochromus niloticus (Nile tilapia), as the main representatives of Lake Tana fisheries. They noted that before 1986 Lake Tana was a subsistence fishery exploited predominantly by reed boat fishing vessels. This type of fishery was limited to the shore areas and targeted the native Nile tilapia using locally made fish traps and small gill nets.

approximately 1800 m a.s.l. in the north-western highlands of Ethiopia, 500 km north of the capital Addis Ababa (Fig. 1). The lake is shallow (average depth 8 m, maximum depth 14 m), and its trophic status is described as oligo-mesotrophic [11]. The lake's fishery is 30 km downstream from the Blue Nile outflows, and is isolated from the lower Nile basin by 40m high waterfalls. Physical and hydrological features of the lake water follow a seasonal pattern. Rainfall peaks in July-August are followed by a rise in the lake water level by 1.5 m, reaching

In their study, DeGraaf et al. [12] identified the three endemic fish species groups Barbs or yellow fish (*Labeobarbus* spp.*)*, African catfish (*Clarias gariepinus)*, and Nile tilapia *(Oriochromus niloticus)*, as the main representatives of Lake Tana fisheries. They noted that before 1986 Lake Tana was a subsistence fishery exploited predominantly by reed boat fishing vessels. This type of fishery was limited to the shore areas and targeted the native Nile tilapia using locally made

In 1992-1993 about 113 reed boats were counted on the lake and about 374 gill nets were in use, with an overall daily haul averaging 12.3 kg (7.8 kg Nile tilapia, 4.3 kg Labeobarbus spp. and 0.2 kg African catfish). Here it is important to indicate that Labeobarbus spp. in this lake is represented

3.47

2.815

Kenyan Water Tanzanian Water Uganda Water Average L. Victoria

 The artisanal fishing gear was in use on traditional fishing boats in Lake Victoria fisheries until the industrial exploitation of the Nile perch for international commercialization. At that time, motorized boats and improved fish gear "even illegal" was used. The most common gear used in Lake Victoria fisheries are gill nets and long-line hooks. During the period of 2000 and 2004, the numbers of gill nets in use increased by 50% reaching 980,000 gill nets, while the numbers of long-line hooks is estimated at 8 million in 2001. This number was adjusted to only 6 million during [6]. The current haul is estimated at 45 kg boat -1 day -1 compared with the 80 kg boat -1 day -1 figure during 1990's. This indicates over-intensive exploitation of the fisheries of Lake Victoria fish resources and argues

Figure 3, Biomass potentials of different water sectors of Lake Victoria for the main three fish

**Figure 3.** Biomass potentials of different water sectors of Lake Victoria for the main three fish species (tons km-2) [8]

The artisanal fishing gear was in use on traditional fishing boats in Lake Victoria fisheries until the industrial exploitation of the Nile perch for international commercialization. At that time, motorized boats and improved fish gear "even illegal" was used. The most common gear used in Lake Victoria fisheries are gill nets and long-line hooks. During the period of 2000 and 2004, the numbers of gill nets in use increased by 50% reaching 980,000 gill nets, while the numbers of long-line hooks is estimated at 8 million in 2001. This number was adjusted to only 6 million during 2006 [6]. The current haul is estimated at 45 kg boat -1 day -1 compared with the 80 kg boat -1 day -1 figure during 1990's. This indicates over-intensive exploitation of the fisheries of

4.215

2.071

4.59

2.363

3.271

). It lies at an altitude of

). It lies at an altitude of

Nile Perch Nile Tilapia Haplochromins

5.451 5.262

4.271

2.373

for sustainable management intervention. 3.2. Lake Tana (Ethiopia)

highest levels in September-October [12].

species (tons km-2) [8]

Tons/Km2

354 Biodiversity - The Dynamic Balance of the Planet

#### Although Sudan is a country with a very large surface area (2,505,825 km<sup>2</sup> ), its inland water bodies occupy only 114,000 km<sup>2</sup> during periods of high water level. The inland fisheries of Sudan are **4. Fish and fisheries of Mid Nile (Sudan freshwater fish and fisheries)**

based on the Nile river tributaries, contributing over 90% of the estimated production potential of the

country. The Sudd swamps in the south (Fig. 1), and the man-made lakes on the White Nile, the Blue Nile, Atbara river and the main Nile river (Lake Nasser portion in Sudan "Nubia") count as the major fishing localities with respect to fish resource magnitude and exploitation thrust [13]. The total fish production of the various inland water bodies and wetlands are estimated at 50,000 tons year -1. This figure is not representative of the full 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 fish production. Although Sudan is a country with a very large surface area (2,505,825 km2 ), its inland water bodies occupy only 114,000 km2 during periods of high water level. The inland fisheries of Sudan are based on the Nile river tributaries, contributing over 90% of the estimated produc‐ tion potential of the country. The Sudd swamps in the south (Fig. 1), and the man-made lakes on the White Nile, the Blue Nile, Atbara river and the main Nile river (Lake Nasser portion in Sudan "Nubia") count as the major fishing localities with respect to fish resource magnitude and exploitation thrust [13]. The total fish production of the various inland water bodies and wetlands are estimated at 50,000 tons year -1. This figure is not representative of the full 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 fish production.

water (55.5 Km3

contribution may be summarized as follows:

motorboats with suitable fishing gear adapted to its bathymetry.

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

*aureus, Sarotherodon galilaeus* and *Tilapia zilli*) as well as *Clarias* spp.

**5.1. Lake Nasser fishes and Fisheries**

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

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

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

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.*

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].

, 5248

The Nile Fishes and Fisheries http://dx.doi.org/10.5772/57381 357


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

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

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.
