Mohamed El-Tahir Ali
Fisheries Research Centre
P.O. Box 1489
|Compared with Lake Nasser, recent applied research on limnology, general ecology, and fishery resources of Lake Nubia has been scant. Fishery development activities, most prominently a fish processing plant at Wadi Halfa, have provided for an increase in fishery output in recent years. However, with a yield of only about 600 t as compared with an estimated potential yield of about 5 000 t, available resources are underharvested. The principal constraints on expansion of the fishery are the organization of fishermen and fishing, capacity of the existing processing plant, but most importantly, transport and marketing of the catch. A joint venture with Egypt includes research on fishery resources as well as a means for expansion of the fishery.|
|La recherche appliquée à la limnologie, à l'écologie générale et aux ressources halieutiques dont vient de faire l'objet récemment le lac de Nubie a été insuffisante si on la compare à celle dont a bénéficié le lac Nasser. Les activités de développement halieutique, essentiellement l'installation d'une usine de traitement du poisson à Wadi Halfa, ont contribué à accroître la production de poisson ces dernières années. Cependant, les ressources disponibles sont insuffisamment exploitées, le rendement n'étant que d'environ 600 tonnes alors que le potentiel est estimé à près de 5 000 tonnes. L'organisation des pêcheurs et des opérations de pêche, la capacité de l'usine de traitement existant et surtout le transport et la commercialisation des captures sont les principaux obstacles qui s'opposent à l'expansion de la pêche. Une entreprise mixte organisée avec l'Egypte comporte la recherche sur les ressources halieutiques ainsi que des moyens pour promouvoir l'expansion de la pêche.|
There is a lack of data, published and unpublished reports on the important aspects of the limnology, ecology, fishes and fisheries of Lake Nubia. Literature available falling into several broad categories, and much of it dated, is listed below.
Physico-chemistry and morphology:
Data on these aspects are mainly from Egyptian sources. Examples of important references are:
Latif (1972), Entz (1974), Entz and Latif (1974), Entz (1976, 1979, 1980a, and 1980b).
Biology of the fish communities:
Fisheries Research Centre Annual Scientific Reports (1967–1979) contain this information and in addition (George, 1971), Abu Gideiri and Ali (1975). Ali and Abu Gideiri are preparing a book on the fishes of Lake Nubia.
Fish populations and fishing gears
Ali (1977), and Ali (1980).
Fisheries management and development aspects:
FAO (1974), Tanmiah (1977), and Ali (1980).
A preliminary investigation has been made by Ali, but not yet published.
El Zorgani, Abdulia and Ali (1979), and El Zorgani and Ali (1981).
General socio-economic studies:
Dafalla (1975), and Greener (1962).
No long-term pre-impoundment investigations were carried out on the Nile River in the vicinity of Lake Nubia. One short-term study on fishes in the vicinity of the second cataract was reported on by Mathiasson (1964).
Many of the common physico-chemical, and biological characteristics of Lakes Nasser/Nubia have been summarized in this volume by Latif and these are not reported here (e.g., Latif (1983) Tables 1, 3, 6; Figs. 6, 15, 20, 21). Results of some periodic physico-chemical samplings over several years from 1971 to 1979 are shown in Table 1, and monthly air temperatures at Wadi Halfa from 1976 through 1981 are shown in Table 2.
The checklist of fishes of Lake Nubia (Table 3) is based on catches of experimental gillnets and on commercial catches using gillnets, seines, and trammel nets.
There are 43 species in 14 families in Lake Nubia as compared with 58 species in 15 families in Lake Nasser.
The relative importance of each species by number and by weight in the experimental gillnet catches is shown in Table 4.
The most abundant families in the experimental catches are the Characidae, Cyprinidae, and Schilbeidae followed by Mochokidae and Centropomidae. In commercial landings, Cichlidae (tilapias) also are abundant.
Centropomidae (Lates niloticus) and Cichlidae (tilapias) are gaining in importance.
Distichodus, Citharinus and Bagrus, species which used to form a major part of the commercial fish catches during 1967–68, decreased markedly and have almost disappeared.
Fish abundance varies temporarily and spatially in Lake Nubia. For example, results have shown that the western side and the southern region of the lake have higher fish catches than other parts of the lake (Abu Gideiri and Ali, 1975).
Relatively Bagrus and Synodontis are abundant during the period March–May. Lates and the labeos increase in abundance with the flood during August and September. Barbus bynnie showed highest catches during January, and again in May–June.
Other biological studies, namely of reproduction, age and growth are still going on, but results are not yet summarized.
Total annual landings from Lake Nubia are shown in Table 5. There has been a gradual increase with time. There was a marked rise during 1973 due to increased private sector activity by the Nile Fishing Company in addition to the initial governmental fishing presence. In 1980 and 1981 there was an increase in fish landings mainly due to the start of production by the Lake Nubia Fishery Project of the Animal and Production Public Corporation.
There are two seasonal peaks of fish production. The first is from February to May and the second from August to October. These peaks are correlated with the warm and the flood seasons, respectively.
The importance of various groups of fishes in the commercial catches is shown on a relative basis in Table 6 and on an absolute basis in Table 7. The importance of various groups has shifted with time. Tilapias now form the most important group, Lates is second and the Labeo species third. Labeo species always have been relatively important in catches.
The changing importance of the various groups has economic as well as biological implications. Lates and Bagrus are considered as Category I fishes, and tilapias along with Labeo and Barbus are second category while other species fall into the third category.
Fishermen employed by LNFP, use exclusively floating gillnets with mesh sizes ranging from 16 to 20 cms, or more. Boats are mechanized, of 2 t and of 10 m in length.
Trammel nets are in common use by the Egyptian fishermen on Lake Nasser. These are used in a specialized form of beach seining to catch almost exclusively tilapias on their breeding grounds in the inlets and shallow beaches. This is now the predominant gear used by the private fishermen. The private fishermen also are using small-size gillnets of from 2 to 8 cm made of the fine twines. These are floating gillnets used in the open waters to catch almost solely Alestes and Hydrocynus to be prepared as wet salted fish. Private fishermen use simple traditional fishing boats of from 6 to 8 m made of wood, or small steel boats.
Data are available from the Fisheries Administration Department only from June, 1981 to July 1982. In summary these are:
Fishing camps: The total number is 23, distributed mainly at “Khors” (inlets) and concentrated at the western and southern parts of the lake.
Fishing boats: In private ownership there are 60 non-mechanized (traditional) and 20 with outboard engines. In addition, there are the mechanized boats of L.N.F. Project (thirtyfive 10-m fishing boats and five 15-m collecting boats).
Fishermen: The total number in the private sector during 1981/82 was 125. In addition, there are 35 to 40 fishing with the L.N.F. Project. The number per fishing unit (camp) is 5 to 7 fishermen.
Price of fish: 20 to 25 pt//kg at Wadi Halfa (Lake Nubia) while at Khartoum the price is 1 to 2 Sudanese pounds.
Three governmental bodies are involved in the development and management of Lake Nubia fisheries:
The Fisheries Administration Department (FAD) of the Animal Resources Division - Ministry of Agriculture and Irrigation:
Fishing is licensed by the Department officials under the General Freshwater Ordinance of Sudan and special local rules for Lake Nubia fisheries.
The Fisheries Research Centre (FRC) of the Agricultural Research Corporation -Ministry of Agriculture and Irrigation. The section at Wadi Halfa is responsible for surveys of resources and assessments of sustainable yields as well as for proposals and measures for fishery legislation.
Lake Nubia Fisheries Project (LNFP) of the Animal Production Public Corporation - Ministry of Agriculture and Irrigation. This is the main body responsible for fish production with an annual capacity of about 1 500 t.
The private sector, in the form of individual fishermen with one or two fishing boats, small companies, and small cooperatives, are supposed to utilize a similar portion of the fishery resource (i.e., about 2 000 t/yr).
Recently, it has been agreed by the governments of Egypt and Sudan to develop a joint venture fishing company to utilize about 1 500 t/yr (i.e., the remainder of the estimated total annual sustainable yield of 5 000 t for the whole of Lake Nubia)
The Egyptian part of the venture is to be taken by MISRASWAN Co., which is the company responsible for fish production and processing on Lake Nasser.
The Sudanese part is to be undertaken jointly among the Animal Production Public Corporation, the Regional Government of the Northern Region, and the private sector.
In view of the above agreement a detailed fish stock assessment research project has been proposed and approved by the two governments to be carried out as soon as possible to provide a better basis for management.
Estimated total sustainable fish yield, as mentioned above, is about 5 000 t/yr (FAO, 1964). Development and management programmes and projects are based on this dated and fairly rough estimate. Lake Nasser, which was originally estimated to have a total sustainable fish potential of about 20 000 t/yr, now has a total annual fish production well above 30 000 t/yr. In contrast from Lake Nubia yield is still below 700 t/yr. Thus, it is safe to say that Lake Nubia fishery resources still are well below optimum utulization.
Wadi Halfa, the only settlement area around the lake after the Nubian exodus in 1964, has now a population of less than 10 000. The Nubians have no tradition of fishing and even regard it as a low status profession. Hence, since 1967, when the first trials for the development and management of the resource were started by the Fisheries Department (at that time it was only one body which included both research and production) attempts to overcome the problem of recruiting fishermen started. Fishermen from central parts of Sudan mainly around the White Nile were recruited to help to train interested locals.
The attempts to recruit fishermen from other parts of Sudan were not successful for the most part because of lack of suitable accommodations and difficulty of integration with the local environment and local population. Since 1981 a purely stopgap solution has been tried by the LNFP. This is the use of army personnel. As a result, some 100 troops are engaged in fishing. This will help to maintain fish production, but of course it cannot be expected that military personnel will become fishing professionals. One solution recently attempted by LNFP is to attract a number of Egyptian fishermen (about 100 of them) to fish for the project as contractors using their own fishing gear. With the help of some of the private sector fishermen acting as contractors to LNFP, the project management is hoping to overcome the lack of fishermen.
At the start it was the policy of LNFP to secure its catch by employing its own fishermen at fixed wages which were sometimes supplemented with a small incentive bonus. At one time during 1979, LNFP even refused to buy fish from private fishermen, hoping to control all labour and production. Attempts failed and LNFP resumed buying fish from the private sector. Reasons for the failure were mainly disagreements and the discontent of the employed fishermen. Incentives were insufficient and the system for payment was not efficient.
LNFP might do better to abandon its policy of catching fish. It should concentrate on purchasing and processing the required quantity of fish from the private fishermen. LNFP could make use of the existing fishing gears, processing and workshop facilities by selling or renting them to the private sector. This would have the advantage of increasing the total income of the LNFP and also stimulate private sector fishing activities.
The daily catches from the fishing camps are collected by boats which carry fish on ice.
Sometimes the quantity of ice is insufficient. No ice is used in the fishing boats and at fishing camps. The time between lifting the nets and arrival at the processing plant is sometimes too long, up to 24 hours.
A modern fish processing plant, financed and installed by the Peoples Republic of China at a cost of about 1.5 million Sudanese pounds is situated about 1 km from the lake shore at Wadi Halfa. The productive capacity of the plant is 1 250 t/yr. The freezing capacity is about 19 t/day and the cold storage capacity is 40 t. The ice plant gives about 23 t/day. The plant has its own power supply and water treatment installations, as well as workshops and storerooms. However, processing and handling facilities are manual.
Operational efficiency in the processing room could be considerably improved by using conveying belts to facilitate quicker and easier transfer of fish. Furthermore, processing machinery (e.g., deheading, gutting and filleting machinery) could be added to raise the present processing capacity. Processing is presently all manual and rather slow, often resulting in much delay and spoliage of fish before freezing.
The wet-salting of fish is carried out only by private sector fishermen. Characidae (Alestes and Hydrocynus spp.) are used for wet-salting. The amount of wet-salted fish is not represented in the total commercial fish landings, but estimates during 1981/82 indicate that about 20 t of wet-salted fish are produced.
Refrigerated railway wagons are used to transport frozen fish (about 40 to 60 percent of the landed fish) from the factory to marketing centres at Atbara, about 600 km south of Wadi Halfa and Khartoum, about 900 km south. There is a pre-sale storage facility for frozen fish at each centre (Atbara, 15 t capacity and Khartoum, 35 t capacity).
Normally, there are two to three trains with refrigerated wagons from Wadi Halfa to Khartoum weekly. The rail transport depends on a single track railway. In the rainy season there are frequent washouts which disrupt the rail connexion for several days at a time.
Marketing of the Lake Nubia fish production is presently limited by lack of transport facilities. In addition to Khartoum District and Atbara town in the northern region, other populated areas of Sudan are potential marketing sites, if transport can be made available and if the catch of fish is expanded. Examples of marketing sites are Dongola, Karima, Shendi and other towns in the northern and central regions of Sudan. Demand for fish generally exceeds the supply.
Abu-Gideiri, Y.B. and M.T. Ali, 1975 A preliminary biological survey of Lake Nubia. Hydrobiologia, 46:535–41
Ali, M.T., 1977 Studies of gillnet selectivity in Lake Nubia fisheries. M.Sc. Thesis, Department of Zoology, Faculty of Science, University of Khartoum, Sudan
Ali, M.T., 1980 Fisheries research and utilization of fishery resource of Lake Nubia. Water Supply Manage., 4:55–61
Dafalla, H., 1975 The Nubian exodus. Khartoum, Khartoum University Press
El-Zorgani, G.A., A.M. Abdulia and M.E.T. Ali, 1979 Residues of organochlorine insecticides in fishes in Lake Nubia. Bull.Environ.Contam.Toxicol., 22:44–8
El-Zorgani, G.A. and M.E.T. Ali, 1981 Hydrocynus forskalii an indicator fish for monitoring DDT pollution in the Nile. Paper presented at the Third Annual Central Meeting of the African Association of Insect Scientists, December 1981, Khartoum, Sudan
Entz, B.A.G., 1974 The morphometry of Lake Nasser and Lake Nubia. Aswan, Lake Nasser Development Centre Project, Working paper (6):137 p.
Entz, B.A.G., 1976 Lake Nasser and Lake Nubia. Monogr.Biol., 29:271–98
Entz, B.A.G., 1979 The appearance of a littoral fauna in Lake Nasser-Nubia, a newly formed tropical man-made lake. Symp.Biol.Hung., 19:201–9
Entz, B.A.G., 1980 Ecological aspects of Lake Nasser-Nubia. The first decade of its exixstence, with special reference to the development of insect populations and the land and water vegetation. Water Supply Manage., 4:67–72
Entz, B.A.G., 1980a Sedimentation processes in the reservoir Lake Nasser-Nubia during 1965–1974 and future aspects. Water Supply Manage., 4:67–72
Entz, B.A.G. and A.F.A. Latif, 1974 Report on surveys to Lake Nasser and Lake Nubia (1972–1973). Aswan, Lake Nasser Development Center Project (RPA/UNDP/FAO) Working paper (6)
FAO/UNDP, 1974 Fish yield projections on the Nasser Reservoir (including Lake Nubia, the Sudan). Report prepared for the Government of the Arab Republic of Egypt by FAO of the UN acting as executing agency for UNDP. Based on the work of R.A. Ryder and H.F. Henderson. Rome, FAO/UNDP, FI:DP/EGY/66/558/Technical report 5:32 p.
George, T.T., 1971 Preliminary account of the fish and fisheries of Lake Nubia during 1967–1968. J.Indian Fish.Assoc., 1(2):68–88
Greener, L., 1962 High dam over Nubia. London, Cassel, 198 p.
Latif, A.F.A., 1972 Technical report on the lake wide survey of Lake Nasser and Lake Nubia. Aswan, Lake Nasser Development Centre Project, 44 p.
Mathiasson, S., 1964 Fiskar och andra vaxelvarms djur Vid Nilen i Sudanesiska Nubien. Sartryck Ur Akvariet, 1964, pp.116–9, 138–42, 157–63. (in Swedish with English summary)
Tanmiah (Independent Consultants), 1977 Feasibility of export-oriented fisheries industry in Lake Nubia. Kuwetti Amadon Nile Co., (in Sudanese)
Table 1. Physico-chemical characteristics of Lake Nubia (summarized from Abu Gideiri and Ali, 1975, and Ali, 1977 and 1980)
|Air temperature range °C)1||15.8–31.5||13.7–34.7||15.1–32–9||18.3–34.3|
|Water temperature range °C)||15.3–27.7||15.7–30.3||16.3–29.9||20.8–28.8|
|Secchi (cm)||25.5–226.7||32.3–166.3||29 –271.5||60–120|
|Free CO2 (ppm)||1–2||-||0–1.2||-|
|Total alkalinity (ppm)||86.7–123.3||90–130||76.7–110.8||58.8–124.2|
1 At sampling times only
Table 2. Average, maximum and minimum air temperatures (°C) at Wadi Halfa (Lake Nubia) 1976–1981 (Source: Meteorological Dept.)
Table 3. Fish species from Lake Nubia over the period from 1967 to 1979
Table 4. Percentage composition of fish species by number and weight based on experimental gillnets of 40 to 200 mm stretched mesh at different sites on Lake Nubia (from Ali, 1977 and 1980)
Table 5. Total fish landings (kg) from Lake Nubia from 1970 to 1981
|198 292||144 428||228 013||424 282||268 575||295 306||285 342||249 093||204 528||355 517||628 915||625 162|
Table 6. Relative (percentage) importance of various groups of fishes in the commercial fish landings of Lake Nubia from 1972 to 1980
Table 7. Total commercial fish landings by groups in numbers and weight (kg) from Lake Nubia from 1972–1980
|Tilapias||n||8 608||3 921||8 374||21 911||56 996||17 483||16 577||16 623||220 536|
|kg||28 075||12 060||17 995||29 371||98 477||29 175||40 175||20 549||399 790|
|Lates||n||6 237||11 064||8 943||10 101||13 837||19 397||13 198||38 121||21 416|
|kg||17 566||40 140||37 346||36 819||51 290||68 232||53 190||139 270||86 426|
|Bagrus||n||2 114||2 043||1 403||2 517||4 613||2 497||1 424||1 296||2 381|
|kg||8 241||7 620||6 658||7 831||15 273||10 326||13 445||5 326||11 274|
|Synodontis||n||24 459||13 936||8 211||8 917||9 380||5 698||4 234||6 969||10 083|
|kg||29 200||19 918||12 704||11 944||11 748||7 970||14 308||10 046||12 638|
|Labeo||n||25 617||30 810||15 390||12 342||23 143||25 853||17 705||23 580||16 141|
|kg||95 854||135 120||74 521||56 606||75 100||101 847||66 626||124 989||67 093|
|Barbus||n||6 779||9 177||5 985||4 862||6 666||7 652||9 726||16 723||14 931|
|kg||20 142||27 645||18 800||15 259||19 594||25 773||16 815||52 442||46 454|
|Others||n||2 795||3 450||1 628||1 228||1 828||1 136||825||862||1 855|
|kg||13 583||11 560||8 585||6 495||8 798||4 602||5 679||2 895||5 294|
|Total||n||76 609||74 401||49 934||61 878||116 763||79 716||63 690||105 184||287 343|
|kg||218 211||254 063||176 609||164 325||280 697||248 156||210 241||355 517||628 915|