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In the rivers of Brazil

Biologists register 2,122 species of fish in the fresh water rivers of Brazil

The movement in the fish stalls at São Paulo’s Municipal Market is small at the start of a hot and sunny Thursday afternoon. When stopping at Box 33, in Lane B, at one of the last left corridors of the market, one could choose among, croakers, sardines, mullets and salmon – all species from the sea, some at times of a meter in length. The only fresh water fish, the pintado (Pseudoplatystoma corruscans), which reaches up to two meters in length, is the solitary star on the shelves full of packed ice. Further on at another stall, Box 29 in Lane C, on display are some tucunares (Peacock Bass), typical of the Amazon, surrounded by sardines, groupers, merluccid hakes and other examples from the sea, very well appreciated by customers.

In a country cut across by thousands of rivers, the scarcity of fresh water fish at the São Paulo Municipal Market may well be strange, if there was not an explanation from the person who has been studying the question for more than twenty years. “The diversity of fresh water fish in Brazil is high, but the majority are small and flimsy species, principally of scientific and ecological importance and of low commercial value”, comments Naercio Aquino Menezes, from the Zoology Museum of the University of São Paulo (USP). The Catálogo de peixes de água doce do Brasil (Catalogue of fresh water fish in Brazi), which he coordinated, presents 2,122 species found in the country’s rivers – almost the double of that which had been listed in 1948 by the American biologist Henry Fowler, in a pioneering study.

From 10% to15% of the species were still undiscovered and are being scientifically described. This is the case of a bluish small piaba of around four centimeters, collected in the upper Xingu and upper Tapajós rivers, in the State of Mato Grosso, endowed with a anal fin that produces pheromone, a substance that attracts females during the breeding season. Or of the dragonichtys, something akin to a Chinese dragon, a catfish that is long and chubby, which gained this nickname because of its lengthy whiskers and protrusive snout – which is around fifteen centimeters in length and in lives in the rivers of Central Brazil, burrowing under the rocks of the rapids.

More than in the sea
In order to complement the previous surveys and to assist with the formulation of public policies for sustainable fishing , the specialists who prepared the Catalogue covered some twenty States, from Paraíba to Rio Grande do Sul, during a five year period. In spite of this effort, they recognize: it is probable that the work is incomplete. There could well exist a further 2,000 species yet to be discovered, believes, Ricardo Macedo Correa e Castro, the coordinator at the Ichthyology Laboratory of USP at the town of Ribeirão Preto one of the Catalogue’s authors, in which there was also participation from teams at the National Museum of the Federal University of Rio de Janeiro (UFRJ) and the Sciences and Technology Museum of the Catholic Pontifical University of Rio Grande do Sul (PUC-RS). Even this present total already overtakes the number of marine fish: along the Brazilian coastline 1,297 species live, presented last year in the species Catalogue of Brazilian marine fish, edited by these same teams from the Zoology Museum of USP and the National Museum of UFRJ (see Pesquisa FAPESP Nº 94 ).

It has been calculated that 25,000 species of marine and fresh water fish exist throughout all of the planet. According to the survey published in 2003 by the PUC of Rio Grande do Sul, the Central and South Americas are home to around 4,400 species of already identified river fish , as well as the other 1,600 that still need to be described. With the 2,122 species of the new inventory, Brazil responds for around 30% of this diversity, as a consequence of the variety of aquatic environments – rivers, creeks, narrow waterways, lakes and lagoons. “The geo- morphological evolution of South America gave rise to the formation of an elevated diversity of aquatic ecosystems that favored the development of a fauna of fish that does not find a parallel in other parts of the world.”, comments the biologist Menezes.

The region with the highest variety of fish – almost one thousand – is, predictably, the Amazon river basin as a result of, in the first place, its very own dimensions: it is the largest river basin in the world, with a drainage of 5.8 million square kilometers, the equivalent of almost half Europe, of which 3.9 million square kilometers are in Brazil. In second place, the very diversity of the environments: there are rivers of three categories, in accordance with their coloration – white water rivers such as the Amazon, the Madeira and the Jamari, clear waters such as the Tapajós and the Tocantins and black waters such as those of the rivers Negro and Uatumã. As well as this, the volume of water is gigantic: of the twenty major rivers in the world, ten are in the Amazon basin. The largest of these, the Amazon itself, with 6,5000 kilometers of extension and a distance between the margins that varies from four to fifty kilometers, and is responsible for 20% of the fresh water that annually flows into theoceans.

Three very large fish symbolize the Amazon. The first is the pirarucu [giant arapaima] (Arapaima gigas), one of the largest fresh water fishes in the world, with length of up to three meters and weighing up to 150 kilograms, of primitive appearance, with a long head and body that thins out until it reaches a rounded tailfin. Another, which also makes up part of the culinary of the North Region, equally served up stewed, is the tambaqui [black pacu] (Colossoma macropomum), carnivorous, with length of up to one meter and weighing up to 30 kilograms. The third is the tucunare [Peacock bass] (Cichla ocellaris), a carnivore that grows up to 80 centimeters and can weigh 15 kilograms, recognized by its rounded black stripe – the ocellus – at its tail. Generally served grilled, or cooked with vegetables, it is the one that can be found most often of the three at the Sao Paulo Municipal Market. Even at that, few are sold. “When a lot, about ten per week”, observes Reginaldo Gomes de Souza, a fishmonger at the stall of Box 29. “Only who comes from the North knows it.”

Lemon and coriander
The second region in diversity of fish, with almost 500 species, is the region bordered by the three rivers: the Paraná, of 4,000 kilometers of extension, the Paraguay, with 2,621 kilometers and the Uruguay, with 1,770. For its size, and, if we were to be just, its flavor, the pintado (Pseudoplatystoma corruscans) is outstanding and highly appreciated when served from a hot charcoal fire, in cubes, seasoned only with some drops of lemon juice. “The lemon takes away the taste of the meat”, warns João Gualberto, an employee at stall 29 of the São Paulo market. He suggested that the pintado can also be made up as a “moqueca” dish, a stew with coconut milk, parsley, onions and – herein lies the secret – a good pinch of coriander.

It is a fish, as they say in the market, that sells well: close to fifty are sold per week. Also in the rivers of this region the dorado (Salminus maxillosus), a ferocious predator that can weigh up to 25 kilograms, is found. In the San Francisco river basin some one hundred and fifty different species can be sighted, among them the curimata (Prochilodus vimboides), of grey skin, a mouth in the form of a sucker and with meaty lips, and the tabarana (Salminus hilarii), known for its pointed snout and for its reddened tail fins.

All of these are commercially explored fish. During 2002, Brazil produced , through catching, 680,000 tons of fish. Of this total, 455,000 tons (67%) came from the sea and 225,000 (33%) from the rivers. Brazil, where fishing activity generates around 800,000 direct jobs, occupies the 27th position in the world market, with growing exports: US$ 120 million in 1998 and US$ 330 million in 2002.

Nevertheless, for the researchers the scenario is not exciting . “Fishing has surpassed the limits of sustainability”, laments Paulo Andreas Buckup, from UFRJ. A report published by the Ministry of the Environment at the end of May, listed one hundred and sixty endangered fish species – one hundred and thirty five are freshwater fish. This verification reinforces the need for redoubled care, especially with the small and flimsy species, classified as scientifically and biologically relevant, which in general live in creeks. As they feed themselves on small invertebrates, fruit and leaves that fall from trees, they become easy victims of the deforestation of the banks of rivers, of pollution and of major civil works such as hydroelectric schemes.

The variety of fish in the Brazilian streams and creeks, up until only a short time ago was little known, perhaps because of their low commercial value, and have only become a little bit clearer from the way in which researchers have been dragging up their nets. In rivers such as the Mogi-Guaçu, Piracicaba and Tietê, in the region of the upper Paraná river, the USP research group from Ribeirão Preto collected some 17,000 examples of fish, which included fifteen new species – one of them is the diminutive Corydoras difluviatilis, which feeds on insects buried in the sand at the bottom of the rivers Pardo and Mogi-Guaçu.

In an Atlantic Rain Forest creek, at the division of the States of São Paulo and Rio de Janeiro, the team from the Zoology Museum again met up with the Trichogenes longipinnis, with a long tail fin and a light brown body with dark markings and other traits, rather primitive in relation to other catfish – having, for this reason, evolutionary importance. “The fact of having a distribution restricted to the Atlantic Rain Forest and to be a relatively primitive species, reveals the importance of the aquatic ecosystems of the region in the historical evolutionary context of fresh water fish in South America”, comments the biologist Menezes.

The expedition to Central Brazil, prioritized as it contains important tributaries of the Amazon basin in little explored regions, was the only one that brought the four teams together. The sixteen researchers disembarked at the city of Cuiabá, the capital of the state of Mato Grosso, on the 15th of January 2002, under a burning sun, ready to confront the rainy reason. When they returned home, fifteen days later, they had covered 5,000 kilometers of potholed and muddy roads. They had caught around 50,000 fish of roughly one hundred species, including seven new families of Loricariidae, which includes the armored catfish – of length less than five centimeters, with a mouth in the form of a sucker and a body dressed with bony cuirass, living hidden under the leaves and tree trunks of the margins of the rivers.

The Projects
1. Knowledge, conservation and the rational use of the fauna diversity of fish in Brazil; Coordinator Naércio Aquino Menezes – Zoology Museum/USP; Investment R$ 1,051,000.00 – Pronex (CNPq)
2. Diversity of fish in the upper Parana river basin; Modality Thematic Project; Coordinator Ricardo Macedo Corrêa e Castro – USP of Ribeirão Preto; Investment R$ 486,037.11 (FAPESP)