Paiche: the invasive fish that advances unhindered through the Amazonian rivers of Bolivia

An artificial hatchery for the fish called paiche (Arapaima gigas) in a lake in the department of Madre de Dios, in Peru, was flooded by a sudden flood of its waters as a result of heavy rains. The currents dragged the young fish to the bed of the Madre de Dios River and there they made their new home. In this tributary they crossed from one country to another and, in 1976, the species was seen for the first time in Bolivia.

However, it has been in the last 15 years that this huge fish has revolutionized the lives of communities that live on the banks of rivers in the Bolivian Amazon, as they have found in it an important engine for their economy.

Despite this bonanza, the ecological problems that this fish probably causes were not enough for the Bolivian government to classify it as an invasive species and, until now, it was considered only an introduced species. To achieve this, experts agree that more studies are needed to see which varieties of fish are at risk from their presence.

In three keys, we explain the situation of this giant of the freshwaters of the Bolivian Amazon.

How is paiche?

This fish native to deep areas in the northern Amazon has no natural enemies in Bolivian rivers. It is a predator par excellence and specimens of enormous sizes with more than 3 meters in length have been observed. The fish can weigh more than 300 kilos and its meat is considered “very tasty”.

It is estimated that its expansion reaches an average speed of 33 kilometers per year. After occupying the Madre de Dios region, the paiche also found in the streams and lakes of northern Bolivia the ecological conditions for their reproduction and eventual dispersal throughout the interior of the country. The paiche lays its eggs on the banks of rivers and its reproduction process takes place successfully in the Bolivian tributaries.

The presence of the paiche in Bolivia has become one of the paradoxical cases of invasion by an exotic species, since in its natural distribution area —Peru and Brazil— it is threatened by predatory fishing. Meanwhile, in Bolivian lands, where other species of fish may be disappearing due to their presence, the emergence and fishing of paiche represents an engine for the economy of the inhabitants of the region.

Catching the invasive fish

Since 2011, the annual paiche catch in northern Bolivia has tripled, and the species accounts for about three-quarters of a professional fisherman’s annual income. Despite the economic benefits it would represent, its impacts on biodiversity are poorly studied and the regulation and control of this issue by the State is notable for its absence.

The paiche occupies a very important place in value chains and has displaced native species in fisheries, such as surubí, pacú and others. Now they are fishing 70% paiche because it is easier”, says Paul Van Damme, biologist and director of the Faunagua Foundation, a non-governmental organization dedicated to the investigation and management of hydrobiological resources and wetlands in Bolivia.

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paiche, invasive fish, Amazon, fishermen, biodiversity
Paiche has become the most profitable option for fishermen in the Bolivian Amazon. Photograph:

use of this species

Of Arapaima gigas everything is used: its meat, its hide and even its tongue. The meat is sold in the main cities of the country and the kilo costs 60 bolivianos (8.5 dollars) in the markets of La Paz.

Handbags, wallets and other accessories are made of leather. This input is processed in the cities of eastern Bolivia and the finished products are destined for export. Its rough tongue is allowed to dry and used as sandpaper or a kitchen grater; it is also pulverized and ingested to fight intestinal parasites, according to traditional culture.

Van Damme details that for many Bolivian fishermen, ecological disaster has translated into economic prosperity. And that is confirmed in the opinion of Jesús Justiniano, fishing leader of the community of Trinidacito, in the department of Pando. “We see paiche as a blessing. Our lakes and rivers in Trinidacito haven’t changed much. The Paiche and other species abound in Lagoa do Mentiroso. We don’t want to exterminate it, it must be maintained because it is the livelihood of several families. If you only catch one, the problem is already solved, instead you should catch many tambaquis. [otra especie de pez] survive,” says the fisherman.

The effects of paiche on other fish and the ecosystem

Van Damme guarantees that there are no investigations in Bolivia to prove which native species were killed by the presence of paiche. The truth is that one of them, the tucunaré (ocellaris)fish that inhabited the Paraguá river, is no longer seen in that area.

We assume that the impact of the paiche is quite large as it is a predator that feeds on native fish. We opened stomachs and saw some, but to demonstrate the impact we have to show the structure of the community before the arrival of the paiche and after”, says Van Damme.

This species, more than any other fish, consumes everything that fits in its huge hooked jaws, in addition to swallowing seeds, leaves, stones and mud. Experts agree that it is a brutal, ecosystem-destroying carnivore.

The few studies carried out agree that, to mitigate the negative impact of paiche, its use must be regulated and controlled —but not eradicated— the species until it does not represent a problem for other species, as they admit that paiche caused the decline of native fish in its passage through the Bolivian Amazonian rivers for more than 40 years.

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