Inland fishery plays an essential role in providing high-quality animal protein at relatively low cost to the population. Estimates of the mean amount of fish consumed by rural floodplain communities vary between 370 g day-1 (Cerdeira et al. 1997)
and 400–800 g day-1 (Batista et al. 1998; Fabré and Alonso 1998) and by urban populations between 50 and 194 g day-1 (Shrimpton et al. 1979; Smith 1979; Santos 1986/87). The Amazon basin has an inland fishery potential of about 900,000 t year-1 (Bayley and Petrere 1989), with inland fishery production recently estimated to be 425,000 t (Bayley 1998). Of this amount, 79% is consumed in Brazil and 20% in Peru. These numbers indicate that the fishery potential of Amazonia is not fully
Fig. 23.3 Multiple regression model to forecast the maximum water level of the Negro River (Manaus) using the mean water level and southern oscillation index (SOI) for February during the period 1903 to 2004 (101 years). The model explains 51% of the variability of the parameters;
only in 3 years (3% of the cases) does the model fail to predict the maximum flood level. The maximum water level is forecast by applying a simple model that uses the relationships between the mean water level in February and the maximum water level (parameters a and b) and the February SOI and the maximum water level (parameter c). Parameters and the standard errors are indicated (Schöngart and Junk 2007). Figure 23.4 in annex
exploited. More than half of the catch is captured by artisanal fishermen and riverine communities for their own consumption. About 20% of the Amazonian population lives in the várzea. The easy access to fish, fruit, and carbohydrates avoids nutritional deficiencies. A portion of the region’s production is sold either at small local markets or to professional fishermen and shipowners, who bring the fish to urban centers. While about 200 species are captured, only 6–12 species make up more than 80% of what is sold at the markets of major cities (Barthem and Fabré 2004).
In the 1970s, an increasing number of fishing boats together with inadequate fishery legislation led to conflicts between riverine communities and professional fishermen, which, in Brazil, could not be resolved by centralized fishery manage- ment. Therefore, by the early 1990s, the Federal Brazilian Environmental Agency (IBAMA) opted to decentralize participative management of the fishery (Fisher et al. 1992; McGrath et al. 1994, 1999; IBAMA 1994, 1997; Ruffino 1996; Isaac et al. 1998), transferring some of the responsibilities and rights to local communi- ties, which assisted in controlling the lakes in their territories and were granted fishing rights in some of the lakes. The fish caught in those lakes can be used for local consumption or sold to professional fishermen (reserva de lagos, acordos de pesca). As a result of these benefits, communities began to protect their lakes. The overall impact of this approach on the local fish stocks and the fishery has not been evaluated yet; however, positive results are expected for the stocks of sedentary species. Migratory species may be less affected while the impact on stocks of large
Fig. 23.4 Comparison between forecasted and observed maximum water levels of the Negro River at the port of Manaus from 2005 to 2009. The time span and difference between forecast and occurrence of the maximum water level are indicated
Table 23.1 Correlation of the minimum water level of the Negro River near Manaus and the accumulated cyclone energy (ACE) index
1950–2005 ACE >117% (n=24) Other years (n=32) T-Statistics Minimum water
level (m asl)
17.04±1.75 18.59±1.89 t=3.19 (p<0.01)
T T T T T
catfish, which migrate between the estuary and the headwaters of the Amazon River system, can be neglected.
Another approach was the delineation of reserves for sustainable management, such as in Mamirauá, where local communities, under the auspice of IBAMA and assisted by scientists, develop and test sustainable management methods.
Experiments with the sustainable management of local stocks of pirarucu (Arapaima gigas) yielded encouraging results, and the method is now being applied also by other communities (Viana et al. 2003). In a multi-species fishery, this type of man- agement of a large predatory species is based on the production of a small amount of a single highly prized species instead of a large amount of many lesser-prized species. This option is only possible in remote areas with comparatively low human population densities.
23.5.2 Fish Culture
Fish culture does not have a long tradition in Amazonia. The Indians stored live fish in tanks (Acuña 1865) but fish culture was not practiced, probably because it was obviated by the abundance of fish in rivers and lakes. The first experiments with fish culture were carried out in Belém, in 1920, by Rudolpho von Ihering, and continued by Pedro de Azevedo in the Brazilian Northeast (Ihering and Azevedo 1934, 1936). Today, 17 species are cultivated in the Brazilian Amazon, three of them exotics: Cyprinus carpio, Oreochromus niloticus, and Tilapia sp.. More than 4,300 culturists, 2,500 of them in Acre, raise fish on a total area of about 3,000 ha (Val et al. 2000). About 60% use extensive methods, only 1.8% practice intensive fish culture. Mean fish production in the state of Amazonas is currently 4.5 t year-1. Tambaqui (Colossoma macropomum) and matrinchã (Brycon melanopterus) are cultivated successfully in tanks near Manaus and fed with pellets. They are sold when fishery supplies are low and prices are high. Tambaqui, pirarucu, and matrinchã are also produced in Colombia, Peru, Venezuela, and Bolívia. During the last few years, catfish (Pseudoplatystoma spp.) have been cultivated successfully in the state of Mato Grosso.
Despite the technological gains, fish culture in Amazonia is still in its beginning stages. A lack of research, insufficient technical assistance, high production costs, and difficult access to bank credits are among the limiting factors (Saraiva 2003).
The availability of large amounts of clean water in most of the basin favors the development of fish culture, but large fluctuations in water availability during the annual cycle poses technical challenges for tank construction, such as excess water during the rainy season, a water shortage during the dry season, and large water- level fluctuations in large rivers and floodplain lakes. The danger of the escape of exotic species is reduced by the successful breeding of native species. However, established methods have been recently threatened by rapid advances in hybridiza- tion technologies. Hybrids often have faster growth rates than their parent species and are thus of particular interest for aquaculture. The negative side effects are that
they may escape into nature and establish viable populations that compete with natural ones, or that they will cross-breed with specimen from natural populations, thus diminishing genetic diversity. Thus, hybrid cultivation in Amazonian fish culture requires intensive research aimed at avoiding these problems, e.g., by the produc- tion of mono-sex hybrids or triploids.
It may be argued that fish culture on a major scale is economically not viable, as long as there is productive fishery for the same species. However, stocks of highly valuable species are, at least regionally, over-fished and prices are increasing; in addition, fish production is highly seasonal, which leads periodically to low supplies.
Fishery is concentrated mainly along the large whitewater rivers whereas new urban centers develop along the new highways, far away from the landing sites of fishing vessels. Here, fish culture has the advantage of low transport costs from producer to consumer.
Today, fish culture in Amazonia remains a complementary activity to fishery, providing high-quality fish at reasonable prices during the entire year. Over the long run, some species, such as tambaqui, pirarucu, and large catfish, have export potential, but this requires large-scale production at low cost throughout the year.
This can, however, be achieved, as shown by Vietnam, which in two decades established a catfish (Pangasius pangasius) culture industry whose current annual production is more than 1 million tons, with a considerable portion being exported. The várzea plays a minor role in fish culture not only because of direct competition with regional fishery but also because of fluctuations in the water level of large bodies of water, which create serious technological problems.
Nonetheless, the availability of cheap fish as food for highly prized carnivorous species, such as pirarucu and large catfish, may provide opportunities in specially adapted lakes.