Abstract
In 2012, a severe drought struck the southeastern of Brazil compromising the Paraná River Basin reservoirs. Here, we described how this climatic event promoted a massive mortality of the giant freshwater mussel Anodontites trapesialis in Furnas reservoir and reported the consequences of this phenomenon. In November 2012, three quarters of 100 m2 were sampled in this reservoir, where 812 dead shells of A. trapesialis were analyzed and measured (33 ˫ 133 mm). The species showed an aggregated distribution with high density ( X ¯ : 1.0 - 5.5 ind/m2). Despite the massive mortality detected in field, it was possible to find living specimens in a small channel in the studied area, allowing the species to survive the water level fluctuations. Large adult individuals (100 ˫ 124 mm) were more affected by drought than juveniles, accounting for about 90% of the dead mussels analyzed. Two years after the massive mortality event, water level was not reestablished and a terrestrial succession (with elevations in the concentration of organic matter and calcium in sediment) was observed in the studied area. We verified that the damming associated with extreme climatic events affect negatively the populations of A. trapesialis and should be faced as a conservationist problem.
Highlights
The giant freshwater mussel Anodontites trapesialis (Lamarck, 1819) is a functional simultaneous hermaphrodite bivalve with a trapezoid shell, with records of some specimens reaching over than 200 mm (Simone 1994, Callil & Mansur 2007)
The present study was conducted at the margins of a portion of the Sapucaí River (20° 58’ 23” S, 46° 07’ 08” W), inserted in the Furnas Hydroelectric Power Station (HPS) reservoir, municipality of Carmo do Rio Claro, Minas Gerais state (Figs. 1 and 2)
In 2012, a severe drought in Brazilian southeast region promoted a sudden change and decrease of the water levels of the reservoir analyzed here. These events have caused a great negative impact on the population of Anodontites trapesialis, evidenced by the expressive number of mussels killed by desiccation, i.e. massive mortality
Summary
The giant freshwater mussel Anodontites trapesialis (Lamarck, 1819) is a functional simultaneous hermaphrodite bivalve with a trapezoid shell, with records of some specimens reaching over than 200 mm (Simone 1994, Callil & Mansur 2007) It is the most widely distributed bivalve in the South America basins, and shows a wide geographical distribution in Americas, occurring from some Central America basins to Argentinean Patagonian basins. This species, which occurs naturally in lotic environments has been commonly found in artificial lakes and reservoirs, especially in areas used for fish farming (Graf & Cummings 2007, Pereira et al 2014, Torres et al 2018) This is due to the fact that their larvae (lasidium type) are capable to use non-native fish species as hosts, as is the case of the tilapia Oreochromis spp.
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