Abstract
The aim of this study was to identify the population structure of the ichthyofauna in an urban stream within an environmental protection area in southern Brazil. Quarterly samplings were conducted between October 2009 and August 2010. Poecilia reticulata was the most abundant species, followed by Hypostomus ancistroides and Rhamdia quelen. It was found a higher proportion of adults instead of juveniles from P. reticulata and R. quelen populations, while the opposite was recorded for H. ancistroides . Sex ratio of 1:1 was found for H. ancistroides, but differed significantly for P. reticulata and R. quelen. Females of P. reticulata and R. quelen reached higher length than males in the smaller and higher length-classes, while H. ancistroides females were only longer in initial length-classes. It was recorded higher occurrence of mature and maturing individuals. Mature individuals of H. ancistroides were sampled in October, and P. reticulata and R. quelen throughout the sampling period. Despite adverse environmental conditions, the occurrence of juveniles indicates reproductive activity for these species. Population structure studies in degraded systems are urgent, since life-history features of species may suffer changes due to anthropic impacts. Providing such information contributes to decision making and management of degraded systems.
Highlights
Streams are small sized water bodies, of first to third order (Allan & Castillo, 2007), heterogeneous environments spatially limited and vulnerable in relation to their biological balance (Braga, Gomiero & Souza, 2009)
Poecilia reticulata (Peters, 1859) was the most abundant species among the 3777 individuals caught, comprising about 90% of sampled specimens (3396 individuals), followed by Hypostomus ancistroides (Ihenring, 1911) (264 individuals or 7%) and Rhamdia quelen (Quoy & Gaimard, 1824) (117 individuals or 3%)
Juveniles of H. ancistroides were abundant in January 2010, and the adults in April 10 and August 10 (Table 2)
Summary
Streams are small sized water bodies, of first to third order (Allan & Castillo, 2007), heterogeneous environments spatially limited and vulnerable in relation to their biological balance (Braga, Gomiero & Souza, 2009). Species living in streams have small size and present a major contribution to the Neotropical biodiversity (Lowe-McConnell, 1999). The majority of the Brazilian streams, mainly the urban, are neglected (Magalhães, Casatti, & Vitule, 2011). In these environments, fish diversity tends to decrease, given the sensitivity of these organisms to Maringá, v. 27-34, Jan.-Mar., 2017 environmental disturbances, such as changes in water quality or the hydrological regime, typical of impacted streams (Cunico, Agostinho, & Latini, 2006). Urban streams are characterized by frequent and strong spates, which contribute to the homogenization of the stream bottom due to the carrying of structures such as branches and leaves (Ramirez, Pringle, & Wantzen, 2008)
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