On the 6th edition of the journal Science Unesp, launched on Friday (5), researchers who plunge into the river Paraná unravel the infestation of rays that used the lake in the Itaipu hydroelectric plant to proliferate and occupy other environments, threatening bathers and fishermen.
When the light went out in much of Brazil on 11 November last year, the fisherman Alfredo Alves Cruz, 32, was about to despair at his home, with my foot throbbing in pain. Earlier he had taken a sting ray was fishing on the banks of the Parana River in Três Lagoas (MS), and at that time was trying, with hot water, ease the suffering.
There is a certain irony in the nature he had crashed on a day of blackout, as the wounded animal that was only because there just 27 years before it was flooded a large area in the State of Paraná to supply the largest hydroelectric dam in the world — Itaipu. The famous Seven Falls Guaira, who swamped in October 1982, historically served as a barrier that prevented the stingrays are common in low and middle Paraná, climbed to the high river.
With the lake created, these fish related to sharks found a new way and rapidly colonized a region that until then know its existence. There are millions of years, stingrays in the Caribbean have adapted to live in the rivers of the Amazon.
From there, the Mato Grosso Pantanal and reached down to the Paraguay-Paraná basin, where they were restricted. Now, the Paraná they have even Island Single, more than 350 km from the starting point of dispersal (Foz do Iguaçu). It also reached the Paranapanema and Tiete rivers.
The relationship between rays and humans has never been very good. The animal is often associated with injuries and coastal fishermen, especially in the north, where these fish live for thousands of years and are quite common – and the population is more than familiar with them. One can imagine what would happen to communities that had never seen the animal before. Was what led Haddad about ten years to start paying attention in cities with river beaches in the Paraná River.
A survey conducted by museum shortly after the sinking of the Seven Falls shown that the rays had risen. Before the formation of the lake, the aquatic fauna of the region of Foz do Iguaçu was 113 fish species, after the flooding, 76 new species appeared on the site, including three stingray. But it was not made any further monitoring to see if they were moving and where.
In the region of Alto Parana has no statistics on the number of accidents, but the perception of the researchers is that they are growing. In fact, when Haddad evaluated the injury Alfredo Cruz, three other fishermen – a small group of five – showed the scars of old stings.
Source: unesp.br
