The African great lakes: Food source and world treasure

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FRYER, G. (1972a). Conservation of the Great Lakes of East Africa: a lesson and a warning. Biological Conservation, 4(4), pp. 256-62, illustr.

THE AFRICAN GREAT LAKES: FOOD SOURCE AND

FRYER, G. (1972b). Some hazards facing African lakes. Biological Conservation, 4(4), pp. 301-2.

To comment on Dr Geoffrey Fryer's papers (1972a, 1972b), with that of Stoneman et al. (1973), essentially requires emphasizing the two vital modern problems that Mankind must solve on the magnificent African lakes. They must at once be skilfully managed to yield protein for ever-increasing populations and conserved in their wonderful biological complexity as a heritage for all Mankind. These two essential needs are, with the use of modern fishery science techniques, not incompatible if both are understood and assigned equal importance. Practical suggestions to achieve these twin aims are urgently needed. Stoneman et al. effectively rebut many of Dr Fryer's statements and allegations, and indeed it is scarcely useful to suggest that lake fishery resources are being mismanaged, without unassailable evidence, or to call years of carefully-planned surveys 'preliminary tests'. Dr Fryer's thinking in general appears to lake little note of African aspirations and problems. African countries, like all the rest, must march with the times, and it is not reasonable to expect hungry populations, rife with protein deficiency diseases such as kwashiorkor, to exist around lakes containing enormous reserves of protein foods that are unobtainable by their present technology. One could as well say that the trawling of the beautiful Plaice offshore in the North Sea is 'indefensible', as it upsets their ecology and prevents numbers of fishermen from making a living by spearing them from coracles in estuaries. The trawl is a tool used by Man the world over to augment his expanding population's food supplies, and Africans alone cannot be denied its use. The answer is, of course, not to 'place embargoes', but to use them wisely, and with all the controls and management practices inherent in modern fishing planning, bearing on the specific problems of any fishery. This, as Stoneman and his colleagues show, is being done on the African Great Lakes. Massive pollution would certainly be calamitous, but no one must be misled into believing that such a disaster is probable. There is no evidence of future eutrophication. The countries around the lakes are poor for good reasons: considerable geological faulting has taken place there. Any valuable stratum is rapidly faulted away, so the lake regions have few mineral resources. There is no coal, oil, iron-ore, or similar factors responsible for such cities as Detroit, and for the concentrations of industries and population that are causing pollution of some of the Laurentian lakes such as Erie. These countries do not casually receive large aid programmes; if they had had the resources,

JACKSON, P. B. N. (1971). The African Great Lakes fisheries, past, present and future. Afr. J. Trop. Hydrobiol. Fish., 1, pp. 35-49.

KITAKA, G. (1972a). Past Trends and Recent Research of the Fisheries of Lake Victoria in Relation to Possible Future Developments. CIFA/72/S.13, FAO, Rome: 4 pp. (mimeographed).

KITAKA, G. (1972b). Some important features of the hydrology of Lake Victoria. Paper delivered at the 1972 annual congress of the Limnological Society of Southern Africa. LSSA Newsletter No. 19, Durban, p. 10. LOWE, ROSEMARYH. (1952). Report on the Tilapia and other fish and fisheries of Lake Nyassa. Col. Off. Fish. Publ., HMSO, London, 1, No. 2, pp. 1-126, illustr. MALAWIGOVERNMENT(1964). Annual Report of the Department of Agriculture and Fisheries for the Year 1963. Fisheries Research (Part H). Government Printer, Zomba: 15 pp. MALAWI GOVERNMENT (1969). Economic Report 1969. Government Printer, Zomba, pp. 36-7. MALAWI GOVERNMENT (1972). Annual Report of the Fisheries Department for 1971. Zomba, Malawi: 33 pp. REGIER, H. A. c~¢KELLEY,D. W. (1972). Fish and Fisheries in the Context of Environmental Concern. First Session of the Committee on Inland Fisheries for Africa. CIFA/72/S.4, FAO, Rome: 8 pp. (mimeographed). STONEMAN, J. & ROGERS, J. F. (1970). Increase in fish production achieved by stocking exotic species (L. Kioga, Uganda). Occasional Paper No. 3, Uganda Fisheries Dept, Entebbe, pp. 16-9.

TARBIT,J. (1972). Lake Malawi Trawling Survey 1969-71. Fisheries Bulletin No. 2, Fisheries Department, Zomba, Malawi, pp. 1-16, illustr. UGANDAGOVERNMENT(1972). Fisheries Department Annual Report 1970. Entebbe: 24 pp. (mimeographed).

WILLIAMSON,R. I . (1966). Analysis of Ring-net Catch Data from the South-East Arm of Lake Malawi, 1946-1966. Malawi Fisheries Department, 4 pp. (mimeographed). J. STONEMAN, Chief Fisheries Officer, Malawi K. B. MEEC.AM, Project Manager, UNDP/FAO Lake Malawi Project, & A. J. MATHOTHO, Project Co-Manager, UNDP/FAO, Lake Malawi Project, Fisheries Department, Ministry of Agriculture & Natural Resources, P.O. Box 593, Lilongwe, Malawi

WORLD TREASURE

Short Communications they would have made themselves wealthier by industrialization long ago. Again, there is no evidence that organic oxygendemanding pollution is a potential threat. The cycle of growth, death, decay, and regrowth, is much more rapid in the African Great Lakes (the 'teeming highspeed realm of tropical aquatic life', as Russell (1953) put it) than in temperate lakes, and there is no severe winter to slow the process down. In the huge epilimnetic regions of these Lakes, organic waste, e.g. sewage, is broken down all-year-around much more rapidly than even the largest human groups there can produce to excess. On all these Lakes there is only one really large human aggregation, the Greater Kampala-Mengo urban complex, estimated soon to reach a million individuals. Its sanitary engineering situation has recently been studied by W H O as part of a master plan for this conurbation, but no gross pollution has been found. A little local contamination may occur, from biocides washing in from plantations in a few areas, or from minor industry, but such cases are carefully watched (FAO, 1971). By and large, pollution is not a major problem on African lakes, though there is some interesting evidence (for which I am indebted to Mr D. Eccles of Malawi) that the hypolimnion (bottom layer) of Lake Malawi is very gradually warming up. If this heating should cause an 'overturn' of deoxygenated bottom waters, extensive fish-kills are possible,* but this is not a man-made phenomenon and seems a possibility only for the distant future. I know of no other threat to lake waters unless it be war. So an objective, factual approach shows that the Lakes' situation is not so bad as might be imagined. It is, for example, not correct for Dr Fryer to say that 'already the rewards for fishing in Lake Victoria have been dramatically reduced'. The gill-net mesh-size controversy which he cited (p. 261) occurred over fifteen years ago, but, in spite of it, ever since, according to Fishery Department records, the overall production from Lake Victoria has actually increased steadily. In 1964, seven years after the lifting of mesh restrictions, the total Lake Victoria catch was estimated at 85,000 tons while, in 1971, seven years later again, the estimate exceeded 110,000 tons, excluding experimental trawling! This error perhaps arose from arguing from the particular of one restricted fishery which happens to be well documented, to the general of the huge Lake Victoria as a whole. The reward of a fishery, or the total catch, and the catch per unit of * Cf. the 'Heavy Fish-kill in Unpolluted Floodplain Lakes of Central Amazonia, Brazil', described by Dr W. L. F. Brinkmann & U. de M. Santos in our April issue (Biological Conservation, Vol. 5, No. 2, pp. 146-7, fig., 1973).--Ed.

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effort, might also be confused. The latter must, of course, be multiplied by the number of units involved. Despite all this, Dr Fryer is undoubtedly correct in stressing the great value and uniqueness of the complex faunas of the Lakes. It is imperative that fishery exploitation cause the least possible harm to this priceless heritage, and undeniable that uncontrolled fishing (usually begun in the colonial era, and often at a critical life-history phase such as a spawning migration) has caused depletion of many stocks. Many cases are not mentioned by Dr Fryer, though they are well documented, and, while differing in no essential from innumerable other examples wherever fishing occurs in the world, surely deserve the most careful attention. Danger may be especially great for a species where there is no economic incentive to cease fishing for it as it is only incidentally caught while other species are being pursued. The Nile Perches (Lates spp.) and the Catfish Dinotopterus cunningtoni of Lake Tanganyika form a welcome additional bonus to the purseseiners fishing for the small clupeid 'sardines' of the Lake. But the fishery is still profitable, even if none of these big predators are caught. In recent years the catches of them have declined, as they have a much longer life-cycle and are at least tertiary predators high on the food-web (Coulter, 1970). But even if they were fished to near extinction, there would be no economic reason to stop the fishery, as it is directed mainly at faster-growing species that can withstand the fishing effort. The situation is analogous to the incidental destruction of porpoises in the purse-seine fishery for tuna in the Pacific Ocean. Here techniques have been evolved which liberate most of the porpoises (Perrin & Hunter, 1972), and, should Lake Tanganyika authorities consider conservation necessary, similar measures could be taken to free some of the Perch and Catfish that are caught with the 'sardines'. The high cost of purchase and operation of trawlers ensure that the fishery will stop or be redirected should stocks become unduly low, but a potential hazard is that some obscure species, of little commercial value in itself, might be inadvertently extinguished because trawling exerts some pressure on it which is not understood by the fishery scientist at the time. Such species must be more thoroughly studied, as I have previously stressed (Jackson, 1972). There may be danger to the assemblage of small, brightly-coloured fishes living in shallow areas of some lakes. A big demand from aquarium enthusiasts has grown up for them, so that they are being hunted by dealers' agents. While this is mostly controlled by fishery authorities, the value of the trade and the laws of supply and demand may, in future, lead to

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evasion of controls, so a potential threat looms for these beautiful creatures. While it is unrealistic to expect an entire lake to be turned into a National Park, a constructive, practical solution to many of these problems would be to establish such parks, on the lines of the successful Marine Parks, together with a suitable background of coastline and hinterland, in selected areas--a possibility which will be further discussed in a later paper. Positive and practical steps are certainly necessary, since the present papers leave no doubt that, with fish, as with other animals, attempts to conserve them by crude blanket prohibitions on hunting and fishing, without a sympathetic and realistic appreciation of local human ambitions and problems, are doomed to failure. Positive results are achieved only by demonstrating the value of preserving and judiciously using the resource as a tourist attraction, export material, or food source, and by using modern resource management technology, combined with encouraging education on the subject, to devise properly-planned procedures for doing this. This approach is successful with the African big game parks and it should succeed on the Great Lakes.

THE LAKE VICTORIA FISHERIES: SOME FACTS AND FALLACIES

As my article on African lakes (Fryer, 1972), while not intended to be polemical, has evinced protests that all is well with the fisheries, it is necessary to produce facts--conspicuously absent from the critic i s m s - t o demonstrate otherwise. As in the original article, my remarks on fisheries are concerned chiefly with those of Lake Victoria. Concerning hydrology: not having the gift of clairvoyance, I cannot share the confident belief that a lack of natural resources--less complete than Mr Jackson (1973) suggests--will remain a permanent obstacle to future technology, and that these lakes will always be safe from pollution. Indeed, a pulp-mill is planned in northern Malawi whose effluent, including strong alkalis, must drain ultimately into Lake Malawi. A similar plant has produced an azoic region in the more resilient Lake Baikal. As previously explained, it is just because temperatures are high that tropical systems are more fragile than temperate ones. Increased productivity in the epilimnion, as in the sewage disposal scheme in Lake Victoria, leads to increased sedimentation and oxygen consumption. The note by Messrs Stoneman et al. (1973) is References interesting but, far from rebutting my statements, as COULTER,G. W. (1970). Population changes within a group Mr Jackson (1973) claims, is singularly lacking in of fish species in Lake Tanganyika following their facts and its relevance to the problem of Lake Victoria eludes me. What it does make clear is that, with the exploitation. J. Fish. Biol., 2, pp. 325-49. FOOD AND AGRICULTUREORGANIZATIONOF THE UNITED vast increase in financial backing and personnel NATIONS (as FAO). (1971). Report on survey of engaged, there should be a concomitant increase in inland water pollution in Uganda, Kenya, Zambia, and Tanzania. Based on the work of Anders E. research results instead of the decline that has occurred Thorslund, Fishery Officer (Inland Water Pollution). in recent years. The most recent reference in my note was not dated 1963 but 1972--a work summarizing FAO Regular Programme Report, 11, iv + 12 pp. FRYER, G. (1972a). Conservation of the Great Lakes of recent developments. East Africa: a lesson and a warning. Biological Mr Jackson rightly insists on 'unassailable evidence' Conservation, 4(4), pp. 256-62, illustr. that fisheries are being mismanaged~ Unfortunately FRYER, G. (1972b). Some hazards facing African lakes. this is easily provided. Figure 1 shows the decline in Biological Conservation, 4(4), pp. 301-2. catch per net of Tilapia esculenta in the Kavirondo JACKSON, P. B. N. (1972). The Lake Victoria Fisheries Research Project, Kenya, Tanzania, Uganda. Interim Gulf fishery until recently when (see below) adequate Report I, FAO, Rome, 23 pp., 5 appendices (mimeo- statistics ceased to be available. (Other relevant graphed). PERRIN,W. F. & HUNTER,J. R. (1972). Escape behavior of factors--incentives, marketing facilities, etc. [see the Hawaiian Spinner Porpoise. Fishery Bulletin, 70, Garrod, 1961; Fryer & Iles, 1972J----cannot be discussed here.) Figure 2 shows the sizes and weights of pp. 49-60. RUSSELL, F. S. (1953). Fisheries research in British individuals caught in nets of different mesh-sizes. colonies. Nature, London, 171, p. 159. Reduction of mesh-size reduces the size of the fishes STONEMAN,J., MEECHAM,K. B. & MATHOTHO,A. J. (1973). caught and, by removing breeding stock, impairs Africa's Great Lakes and their fisheries potential. recruitment. The 3½-inch nets indeed catch some Biological Conservation (in press). individuals before maturity! The freely permitted use P. B. N. JACKSON, of small-meshed nets is gross mismanagement. A Senior Research Fellow, similar catastrophic decline in both total catch and The J. L. B. Smith Institute of Ichthyology, catch per net of T. variabilis in a well-studied area, Rhodes University, from almost 1.4 per net in 1962 to less than 0.2 per Grahamstown, C.P., net in 1967, and the earlier history of exploitation of South Africa