8. HATCHERIES FOR PRODUCTION OF FISH FOR STOCKING AND FISH PASS INSTALLATIONS

Brazil's 1927 Act, which provided for the installation of fishways in dams constructed in rivers and streams, led to controversy which resulted in its amendment (see Section 7.2). Under the amendment it became possible to choose another type of measure to offset the negative effects of the dams on migratory species - fish hatcheries, for instance. Brazilian fishery biologists' success with several “piracema” species in the field of induced breeding meant that preference was in fact given to hatchery construction. Machado and Alzuguir (1976), who prefer hatcheries to fishways, sum up their argument as follows:

1. Fish in Brazil's large catchment basins are not anadromous. Except for “piracema” fish, they all live and breed in environments where water circulation is low. They form shoals during the spawning seasons and undertake migrations in the rivers and streams. When they come upon a natural or man-made barrier which impedes their passage, they try to surmount it and if they do not succeed, they breed in a suitable backwater below the obstacle.

2. Fishways allow numerous species to pass over these barriers and low quality specimens predominate in the reservoirs.

3. Fishways are very costly installations.

4. The fishway entrance, downstream, should be located at the lowest possible level, otherwise, the fish would not be able to enter the system at low water. Since the fishway would be operating like a weir continuously, it would not be possible to retain water if this were necessary. Fluctuating level pool and weir installations are costly to build, operate and maintain.

5. Fishways in dams over 8 m in height are inefficient.

6. Fishways do not allow for selection of species.

7. Generally speaking, reservoirs contain a majority of harmful species (e.g. Serrasalmus spp.) or species of little commercial value. Fish culture can re-establish the original balance.

8. Basic studies carried out with a view to introducing species into the new medium have beneficial side-effects. They provide data as to the suitability of the water for human consumption, recreational purposes and other uses.

9. Under aquaculture conditions, it is now possible to achieve almost zero mortality, optimal growth and production. In natural aquatic environment this is still not possible.

10. Hatchery seed production is more efficient and the investment involved is smaller than that required for a fishway.

11. The selection of species which meet desired objectives can lead to fisheries development and socio-economic improvement in the region concerned.

12. Culture-based fishery does not interfere with other uses to which the dam may be put.

13. Rational fishery exploitation provides economic and social benefits, makes for catch diversification and is an incentive to fish culture experimentation which could lead to the introduction of new and better species.

These are the arguments which have been and, to a lesser extent, are still being used in Latin America to justify the establishment of hatcheries for seed production. Some of them are totally or partly false, others need adequate technical justification, whilst those which refer to the economic and social benefits to be obtained are rather emotional in tone. No mention is made of the different types of fish pass installations or mechanisms which could be used and their relative costs or of the type of fish culture to be established and the economic and social framework within which it should be established.

Production of material for stocking in hatcheries (planned or operational) in Argentina and Brazil bears usually no relation to the size of a reservoir. The ration of the size of the reservoir to the size of the hatchery can be anything between one and four orders of magnitude (Table 2). The reason for these considerable differences are not clear.

Bonetto (1980) says that fish pass installations and hatcheries should complement each other. Poddubnyi recommended that the two be combined for the Middle Paraná Project, basing his argument on the Soviet experience (Poddubnyi, Espinach Ros and Oldani, 1981; Poddubnyi et al., 1984). This combination has also been recommended for several large dams which are under construction in Argentina (Boiry and Quirós, 1985). The following are some of the most relevant arguments in favour of using fish pass installations in conjunction with hatcheries in order to obtain a fish community closely resembling that found in the original river:

• Not all the species of ecological and/or economical importance can be expected to ascend the fish pass with the same degree of efficiency. It has been seen worldwide that modifications are often necessary to increase the handling capacity of the installations and to allow more species to use them. Because of this, it would be advisable to have a hatchery which could help to provide a suitable fish community.

• Although induced spawning technology has been developed for numerous native Latin American species (Table 3), for most of them the problem of large-scale rearing to the juvenile stage has not been solved. More time and effort is required, which means that it would be advisable to have installations for passing fish upstream, while rearing technologies were being developed.

• Latin America's large catchment basins are shared by two or more countries. When, in addition to existing dams, those under construction or in the planning stage have been completed, virtually all the large rivers will disappear. In their place there will be a chain of reservoirs (see OEA, 1985). Many existing dams have either not been equipped with fish pass installations, or, if they have, these do not work efficiently. Some others have been or will be provided with fishways. This is because there are spawning and rearing areas in the main channel or the main tributaries upstream of the dam. With the construction of reservoirs upstream, the number of these spawning grounds will, in many cases, decline or they will disappear entirely. The long-term, albeit temporary, solution, still within the framework of shared basin management, would be for fish passes or other mechanisms such as floating facilities for storage and transport to be used in conjunction with hatcheries producing material for stocking.

Table 2

Hatcheries for production of material for stocking already constructed or scheduled for construction with the aim of reducing the negative impact of dams on fish communities in Latin America

(a) Machado, 1976;
(b) Alzuguir, 1976;
(c) EBY, 1981;
(d) Poddubnyi et al., 1984;
(e) Hidroservice - Hidrened, 1976;
(f) Boiry and Quirós 1985

Table 3

Induced breeding in Latin American fish species (Luchini, pers. comm., 1985)

^a           ( ) Equivalent in English
^b           Breeding begun
HCG:    Human chorionic gonadotrophin
ACG:    Animal chorionic gonadotrophin (animal not specified)