The Symposium on the Development and Exploitation of Artificial Lakes, held in conjunction with the second session of the Commission on Inland Fisheries of Latin America, took place on 30 November and 1 December 1981, in the Hotel Plaza Dominicana, Santo Domingo, at the invitation of the Government of the Dominican Republic. In a joint opening, the Symposium and the Session were brought to order by Mr Juan Portorreal, Dominican Republic who then introduced Mr Napoleon Padilla, Representative of FAO to the Dominican Republic who, speaking on behalf of the Director General of FAO, Dr Edouard Saouma, welcomed the participants. He briefly described the development and recent state of the world's fisheries, and, in this context, described the considerable progress which had been made in the Dominican Republic in aquaculture. Development of aquaculture started in the 1950's with the establishment, with FAO assistance, of the Fish Culture Station at the Hacienda Maria, now the Experimental Fishculture Station of Nigua. He noted that the last three years had been particularly fruitful, resulting in the training of a group of young professionals and the establishment of several large farms.
Mr Narciso Almonte, Director of Fishery Resources, Dominican Republic, told the participants of his own satisfaction that the meeting was being held in the Dominican Republic and welcomed the participants on behalf of the Department. He then introduced Mr Hipolito Mejia, Secretary of State for Agriculture. Mr Mejia welcomed the group on behalf of the Dominican Republic. He described the emphasis given by his government to a search for new roads to development which would ensure control of the country's resources by its own people and hence greater benefit to the country, especially the most needy. He described in a more detailed way the fisheries problems existing in the region, noting the relatively poor marine resources, and the dangers of pollution, especially from oil. These, he explained, made it especially important for the Dominican Republic to more fully utilize its rich hydrologic resources for fisheries and aquaculture.
After the opening ceremony, the Symposium reassembled, under the chairmanship of Professor Irma Vila Pinto who was introduced to the participants by the Secretary of the Symposium, Dr F. Henderson. In her opening remarks, Professor Vila stressed the importance of countries taking full advantage of such opportunities as the Symposium to share their experiences as fully as possible. She noted that technological progress had been rapid in Latin America in the area of water management and river basin development, but that, unfortunately, the engineering aspects have developed faster than ecological and biological knowledge. Those working with fisheries have not been able to take full advantage of these engineering developments for lack of adequate information concerning the possible integration of fisheries into such schemes. Prof. Vila also stressed the need for participants to keep in communication with each other after the Symposium, if real progress is to be made. The Chairman reminded the participants that the most important objective of fisheries studies in the region is to promote better use of aquatic systems to meet the needs of the rural peoples who live near them.
Turning to the first topic of the Symposium, the Chairman asked that participants provide the Secretariat, to the extent possible, with a list of the reservoirs and impoundments in their countries. These lists might then form the basis for an inventory of artificial aquatic ecosystems of Latin America.
In view of his wide experience, Dr Alberto Nani was invited to begin the presentations by reviewing his own knowledge of the fish populations of reservoirs in Argentina and other countries of Latin America. He briefly described the river system of Argentina, pointing out that their drainage basins were shared by all of Argentina's neighbours. He summarized the studies going on in each of the major river systems, pointing out a number of kinds of problems which have arisen in the course of his work. These included the large number of different species occurring in these river systems, differences from place to place in important characteristics of individual species, and the variety of migratory behaviours shown by the different species. Noting that it was not possible to study all of the species in detail at the outset, he then described the more important characteristics of those to which Argentina had decided to give first priority, such as some of the large catfish, atherinids like the pejerrey, and the established salmonids. Dr Nani called attention to the problem of having to decide whether to turn to non-native species for culture, with the advantage of a considerable background of information, or to use potentially more appropriate, if less understood, native species. Among the questions to be considered is the type of market to be supplied. In some parts of Argentina only an exportable fish can be considered as the local inhabitants do not normally eat fish. Responding to a question by the Chairman, Dr Nani advised that the most important information needed about each species is what it eats, while determination of its growth rate was also important in assessing their fishery and aquaculture potential, and to make the first decisions about managing their exploitation.
F. Zuna described the present state of knowledge concerning the fish and fisheries of the rivers and artificial lakes of Bolivia. He pointed out that there are some 14 000 km2 of inland waters in Bolivia, but only about 0.3 percent of this area is in reservoirs. The reservoirs, more than half of which are at altitudes greater than 3 000 metres, have been stocked with exotic species (rainbow and brown trout, pejerrey and common carp) for practical reasons. In the lowland areas there are numerous small reservoirs (up to 1 ha) into which various species have also been introduced, mostly by local farmers. In anticipation of the completion of an 800-ha hydroelectric dam near Tarija, studies are currently underway to determine what species, if any, should be stocked to create a commercial fishery. The pejerrey was successfully introduced from Argentina to the “Represa Mexico - La Angostura” near Cochabamba where eight part-time fishermen supply fish primarily to nearby markets. Both this reservoir and Corani, also near Cochabamba, appear not to be intensively fished. Lake Uru Uru, a shallow semi-artificial lake recently formed in the delta of the river Desaqquadero at Lake Poopoo, was also described. Here the pejerrey was also introduced, the native Orestias having little commercial value. The lake now supports 110 fishermen, all of whom were displaced from lands flooded by the new lake. However, the gear and boats used are primitive and the fish are not eviscerated before being marketed. Biological studies underway suggest that the resource is underexploited and hence plans are underway to develop the fishery through improvement to equipment and processing.
Mr Zuna's presentation evoked considerable discussion concerning the suitability of pejerrey (Basilichthys bonariensis) and related atherinid species for stocking in reservoirs in the temperate region of Latin America, and about stocking policies in general. Several relatively unsuccessful introductions were described (e.g., Tilapia/Sarotherodon interfering with Colossoma in certain small impoundments and the introduction of the rainbow trout to Lake Titicaca). Successful introductions were also mentioned in the discussion, such as the introduction of the “Guapote tigre” to two artificial reservoirs in El Salvador. The Chairman then reviewed her studies on the biology of the pejerrey, noting that it could reach a very high abundance in the Rapel reservoir in Chile. She described a number of other characteristics which could make it useful in intensive aquaculture as well as for stocking larger temperate reservoirs.
Shifting to more tropical reservoirs, Mr Francisco Geraldez described those of the Dominican Republic, which consist of two quite different types - those close to the sea and those inland at high elevations. He presented a list of the species of fish and commercially important shellfish known to occur in the Republic and described several partificular problems upon which he and his colleagues were working.
After the ensuing discussions, which primarily concerned the need for establishing better guidelines for management of reservoirs both in the Dominican Republic and elsewhere, the Chairman invited participants to prepare lists of important species in the reservoirs of their own countries, similar to that prepared by Mr Geraldez. It was suggested that FAO use these as a starting point for the preparation of a comprehensive list of species useful in reservoir management.
Dr Cordini opened the Second Session of the Symposium by describing the situation in Argentina. Here some major dams have already been installed on the various rivers of the Rio de la Plata and eventually a total of 15 dams are planned to convert the whole system into a cascade. The major problem that the eventual modifications of the river system will cause is the barring of passage to migratory fishes. Migrations within the Parana and Uruguay rivers are very extensive (up to 2 000 kilometres), extremely complex and poorly understood. Fish of the same species may at any time of the year be moving upstream, downstream or even remaining static. These migrations have been thought to be essential for successful reproduction but for some species fish have been found to be producing young without migrating and this contention may thus be questioned. In any eventuality, existing laws demand that fish passes be incorporated into dams to facilitate the passage of migrating fish. Passes under consideration in Argentina include fish ladders, fish lifts of the Borland type, mechanical fish lifts or combinations of these. The efficiency of such structures may be questioned as few examples of successful fish passes exist in the tropics; and the fish ladders already in use at Lucio V. Lopez, Andina, Carcarana and Salto Grande dams have proved largely unsuccessful even though some of the dams only measure 7 m in height. Large populations of fish build up downstream of the dams as well as at Chocon, Itaipu and other smaller dams. A further limitation to the construction of successful fish passes is the lack of knowledge of the migratory behaviour of the various species involved. Migratory pathways differ between species, some of which migrate at the surface, some near the bottom, some near the bank and some near the centre of the channel. The construction of a fish pass suitable for all behaviours would be difficult. An alternative to fish passes for the repopulation of reservoirs from the river downstream may be the extraction of ripe individuals from the aggregations downstream of the dam for artificial reproduction by hypophysation. The young fish could then be reared in ponds prior to their stocking into the reservoir.
The availability of fish species suitable for the population of reservoirs in Latin America was questioned by the Secretariat as many of the reservoirs in the Continent have developed fish communities totally unsuited for fisheries. Typically, such populations are dominated with piranas and small trash fishes. In the north of Brazil reasonable levels of production have been maintained only by the elimination of such species and by the introduction of tilapias more adapted to the lentic environment. However, Dr Nani stated that in Argentina some dams such as that on the Onda river have concentrations of Prochilodus, Astyanax, Salminus, pimelodid catfishes and indigenous cichlids. This may indicate that the capacity of the more temperate river faunas are sufficiently resilient as to populate such waters.
Downstream of the dam, the risks to the fish populations are increased. Here the cessation of the flood that follows dam closure results in a reduction in flooded areas and the lack of conditions suitable to the trigger breeding. This often results in a drastic reduction in species abundance and diversity and the replacement of indigenous fish fauna with more resilient introduced species. Dr Henderson remarked that there is some evidence that this could to a certain extent be avoided by the release of a small artificial flood at appropriate times. There is, however, insufficient experience upon which to predict the magnitude of flood required to stimulate reproduction.
No other countries present at the Symposium had any information on the downstream effects of dams to be installed within their areas although the study of such effect will be included in planning for the future.
The third session on the planning and development of fisheries in reservoirs, began with a discussion of the potential and actual production of fish in the Dominican Republic presented by Mr Gutierrez. Eighty percent of the actual catch in inland waters in the Dominican Republic is made up of Tilapia/Sarotherodon spp. and another six percent of other exotic species. The dominance of non-native species provoked considerable discussion about the pros and cons of the use of exotic species.
J. Hernandez described the present programme in Mexico for the alleviation of hunger through the development of fish production in small reservoirs. Because of the gravity of the problem, the government has initiated a very large-scale programme of pond and reservoir construction, loans and extension. The strategy also includes the use of agricultural wastes as fish feeds, development of such marketing facilities as required, and studies of potential problems such as pollution. This present approach contrasts sharply with previous programmes where emphasis was given to large-scale stocking of reservoirs, but with insufficient follow-up to assess the impact of the programme on fish stocks, or more importantly on the consumption of fish in the rural areas where it was intended that it should go.
N. Almonte strongly supported the points of view previously presented, emphasizing that the most important objective in the Dominican Republic was to provide animal protein for those who now have very little. He mentioned a small group of peasants who were displaced by the construction of a dam in the western part of the country. The Government helped them set up three fish cages and to stock the reservoirs and cages with fish. Thirty-five peasants now obtain about 25 kg/day of fish. He noted that they wanted to extend this approach to other places and to find still other ways to effectively manage these small reservoirs.
A general discussion of the problems of communication between scientists, planners and production workers then followed. It was agreed that this was a serious problem. The participant from Mexico noted that it is possible to coordinate the activities of these disparate groups, but that it was necessary to take into account the different paces of work in science and in production. Discussions between groups are important, and also frequent reports. Mr Tapias emphasized that the results of the dialogue had to be communicated to the highest level of government in order to get a policy established. Mr Forte noted that Guyana was solving the problem of utilizing 11 000 km (7 000 miles) of waterways and 2 000 ha (5 000 acres) of waterways by combining all these functions under one agency. The agency also included marketing among its responsibilities. This meant that the whole operation could be made economically profitable.
Mrs Tejeda, of the Dominican Republic, began the session by describing the programme of the Institute of Cooperative Development (INDECOOP) at Laguna Redonda, in the north-east part of the country, based on tilapias. The institute is primarily concerned with marketing but also assists the fishermen in acquiring boats and nets. The fish produced are filleted by the cooperative and marketed through the Institute.
This provoked a discussion of the possibility of utilizing the wastes when fillets are required for the market. The effects of substituting the government as “middle man” for the traditional ones was also questioned. It was pointed out in this case that the market was in fact a government institution. The price was set to make sure that the fishermen received a fair return.
Mrs Gormez de Pena discussed the history of the use of Sarotherodon (Tilapia) mossambicus in the Dominican Republic. While the early results were not encouraging, the species has now become very important, and is fished wherever it is found. There are many places in the country, such as the mountainous areas, where fish is very badly needed. The government has therefore established a programme of building small reservoirs for fish production. While S. mossambicus has been mainly used, S. niloticus and others are now being studied for such use.
There were a variety of opinions expressed concerning the advantages of various species and stocks of tilapias, some new varieties having better shapes for filleting and higher growth rates. However, these improved varieties involve much more effort in rearing fry and producing fingerlings. It was noted that cage culture of tilapias may be particularly economic when the natural production of a reservoir is sufficiently high to provide the main supply of food.
Mr Bortone reviewed the work going on in aquaculture in Venezuela. Noting that importation of non-native species is prohibited by law in Venezuela, he described the selection of local species suitable for aquaculture. Four species have shown considerable promise: Colossoma macropomus, Colossoma brachipomunm, Prochilodus reticulatus (and P. mariae), and as yet not well defined species of Curimatidae). The first problem has been to attain mass artificial production of fry as none of the species reproduce naturally when confined. This has now been accomplished with the Colossoma species and several trials have been made with the young produced, both in experimental tanks and in two reservoirs in which the species did not occur naturally. The results have so far been good, and commercial trials are being started.
The discussion exposed a considerable interest in Colossoma sp. which have a varied feeding habit and are excellent fish for eating. The participants were invited by the Peruvian delegation to send any available data on these species to them, as they are compiling such information.
Mr Hi Cielo then discussed the research which is currently being carried out on the continental waters of Peru. Priority has been given to Lake Titicaca and the Amazonian basin. Unfortunately, the present limitation of funds has prevented work on the dams and rivers of the coastal area, and the work on aquaculture has been confined to the Huachipa station, and on the advisability of introducing S. niloticus and the Chinese carps to the reservoirs of the coastal areas. There are at present four main reservoirs and a total of 10 000 ha in which fisheries should be developed. It was also noted that work was being done on Colossoma for use in the approximately 200 irrigation reservoirs in San Martin. It was further added that an experiment on fertilization of small reservoirs was also in progress. Early results suggest that manured ponds with phosphate added are most productive of plankton.
The discussions of the Symposium brought out several topics of wide interest. Predominant among them was the need to find more satisfactory ways of determining rapidly how to more effectively utilize reservoirs and impoundments of whatever size to achieve specific goals, especially that of providing food and work for hungry people. While many approaches had been described during the Symposium, there was clearly a feeling that the different approaches, however appropriate, were selected in a rather hit-or-miss fashion and that there was need for a more orderly approach.
Also emerging from the Symposium was a recognition that much of the work of inland fishery development was being carried out by individuals working in near isolation. Not only is there too little communication between countries in the region, but there is also too little coordination and cooperation of efforts among the scientists, planners and the production personnel within countries.
There were also a number of problems which had a clear sub-regional character. These included the problem of providing fish ladders that would work for a wide variety of species whose migrations were threatened by dam construction, procedures for the selection of native species for stocking or culture purposes, and the urgent need for more detailed information on the differing groups of species occurring in different areas.
The discussion also highlighted the importance of assisting the member governments to appreciate more fully the opportunities for increasing local supplies of protein and providing employment, especially in more remote areas, through the development of reservoir fisheries.
The following specific recommendations were the result of the above conclusions.
That the FAO Secretariat propose an outline of a methodology for evaluating the potential of reservoirs for fisheries and for identifying and selecting among alternative strategies for the organization and development of such fisheries. Using this outline as a basis, a small group of experts of COPESCAL should be assembled to discuss and develop this outline as the basis of a handbook or manual on the development of fisheries of reservoirs and small dams in Latin America.
That one or more individuals from the Latin American region be identified to adapt, and translate into Spanish, appropriate documents on pre- and post-impoundment planning for fisheries development in reservoirs and small impoundments, upon the ecological problems resulting from their construction and upon comprehensive and integrated approaches to their development. The Secretariat should also seek means with which to hold at least one workshop in the region on planning fishery development in reservoirs.
That member governments prepare inventories of their dams and reservoirs with an indication of their principal hydrographic and limnological characteristics, and the nature of fishery activities on them, according to a format to be provided by FAO. These inventories will be compiled by the Secretariat with a view to issuing a publication in the COPESCAL series. Member governments should equally prepare lists of species of fish for intensive aquaculture and capture fisheries in dams and reservoirs. These will be distributed, by the Secretariat, to member countries.
That COPESCAL establish a Working Party on Aquaculture (a) to keep under review the various problems of developing fresh-water aquaculture in Latin America, (b) to promote exchange of experiences among countries of the region with particular reference to the development and use of appropriate forms of aquaculture in rural development, and (c) to recommend to COPESCAL specific programmes of regional action. It was further suggested that, in connexion with the next session of COPESCAL, a two-day workshop be held on the planning of integrated and well-balanced programmes for rural aquaculture developments including consideration of economic and social issues.
That COPESCAL, through the FAO Secretariat, seek to cooperate closely with the activities of the regional Man in the Biosphere (MAB) programme coordinated by Unesco.
That the Secretariat, with the cooperation of member governments, identify someone willing to compile the specialized terms of the Spanish language used in inland fisheries, and suggest a standardized use of those terms which are most frequently confused.
That COPESCAL encourage the preparation of synopses of life history and the ecological data needed to manage the important commercial species of Latin America, with special emphasis on native species useful for reservoir fisheries, or for more intensive aquaculture. Of particular and immediate interest are the pejerrey and related atherinids, and the various species of Colossoma, Prochilodus,Brycon, Petenia, etc.
