Abstract
ABSTRACT A field study of the sex ratio, length-weight ratio, body size at first gonadal maturation, and the breeding season of the red-tailed catfish, Phractocephalus hemioliopterus, was carried out in the region of the middle Xingu River in the eastern Amazon basin. The fish were sampled quarterly from September 2012 to January 2014 using gillnets and long lines. The sex ratio was balanced, and while males and females were similar in standard length, the females were heavier than the males, on average. The males presented negative allometric growth, and the females, isometric growth. The estimated size at first maturity was 77.8 cm. The variation in the gonadosomatic index and the greater frequencies of mature specimens indicated a reproductive peak at the beginning of the high-water (flood) period. As P. hemioliopterus is an important commercial fish, our findings will contribute to the future development of effective conservation and management strategies, such as minimum catch size and a close season that is appropriate for the region. These data will also provide important insights for the evaluation of potential impacts on the biology of this fish resulting from the construction of Belo Monte dam.
Highlights
The family Pimelodidae comprises more than one hundred valid species of freshwater fish (Frickle et al, 2019), which are all endemic to the Neotropics, with the highest diversity being found in the Amazon, Paraná and Orinoco basins, and the principal rivers of the Guianas (Lundberg, Littmann, 2003)
Sex ratio of the red-tailed catfish, Phractocephalus hemioliopterus, specimens collected from the Xingu River in Pará, Brazil. *indicates a significant difference between males and females
Parameters of the sinusoidal equation for the Gonadossomatic Index (GSI) values recorded for the redtailed catfish, Phractocephalus hemioliopterus, specimens collected from the Xingu River in Pará, Brazil. *indicates a seasonal trend in the curve
Summary
The family Pimelodidae comprises more than one hundred valid species of freshwater fish (Frickle et al, 2019), which are all endemic to the Neotropics, with the highest diversity being found in the Amazon, Paraná and Orinoco basins, and the principal rivers of the Guianas (Lundberg, Littmann, 2003). Many of the larger pimelodid species are long-distance migrators (Godinho, Kynard, 2009; Hauser et al, 2018) that travel considerable distance to spawn, and are an important source of animal protein for many human populations throughout tropical South America. These fish are mainly species of the genera Brachyplatystoma and Pseudoplatystoma (Barthem, Goulding, 1997; Barthem et al, 2017; Pérez, Fabré, 2018). This species is a medium-distance migrator, typically traveling 100-1,000 km, is one of the most important species for sport and commercial fisheries
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