Abstract
Steindachneridion melanodermatum, an endemic and endangered species, is the largest catfish in the Lower Iguaçu River basin. Currently, the wild population of this species no longer exists in most of this basin, probably due to the loss of habitat by successive hydroelectric dams. This study evaluated the spatial distribution and abundance of S. melanodermatum in the last free-flowing river stretch of approximately 190 km downstream from the Salto Caxias Dam, upstream of the Iguaçu Falls, as well as some tributaries. Hydroacoustic and fishing campaigns were performed between September 2010 to December 2016 to characterize the preferred habitat. A total of 180 specimens was sampled with higher abundances in a protected area near Iguaçu Falls in the Iguaçu National Park. Twenty-four deep pools were identified with maximum depths ranging from 5 to 25 m: 21 pools were along the main channel of the Iguaçu River, and three pools were in tributaries. Deep pools are preferential habitats for this species, especially the deep pool called Poço Preto (P23) and its surroundings. Conservation strategies are required to protect these habitats and prevent S. melanodermatum from becoming extinct, such as establishing deep pools as ecological sanctuaries, intensifying the inspection of illegal fishing, and maintaining dam-free tributaries.
Highlights
Steindachneridion melanodermatum is a large catfish (>150 cm in total length) of the family Pimelodidae and is one of the six endemic and endangered species of the genus [1,2].Its geographic distribution is restricted to the Lower Iguaçu River basin [3,4,5,6], where it is known as surubim do Iguaçu, bocudo, or monjolo
The Lower Iguaçu River is characterized by a high drop with rapids and waterfalls, such as Salto Santiago (40 m), Salto Osório (30 m), and Salto Caxias (67 m) [41], which enabled the formation of five hydroelectric reservoirs in sequence in the main channel of the Iguaçu River [4,40,42]
Habitat changes and degradations caused by the hydroelectric plant, high anthropic pressure, and illegal and predatory fishing [9,22,36] along the main channel and tributaries may have contributed to the low abundance in this area
Summary
Its geographic distribution is restricted to the Lower Iguaçu River basin [3,4,5,6], where it is known as surubim do Iguaçu, bocudo, or monjolo. This species is the largest fish in the Iguaçu river basin and is possibly migratory [4,7,8], inhabiting free-flowing river sections with fast waters, rocky bottoms, and high depth [3]. Lower Iguaçu River basin, probably due to the increase of the anthropogenic pressure derived from the loss of habitats to successive hydroelectric dams in this basin [8,9].
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