Occurrence of the marine catfish Genidens machadoi (Siluriformes, Ariidae) in the Tramandaí lagoon, southern Brazil

Abstract

The catfishes of the family Ariidae inhabit tropical and subtropical regions around the world, including marine, estuarine and fresh water systems. Most of the species use estuaries and downstream portions of the rivers during the breeding season, for spawning and egg incubation. In the Rio Grande do Sul State, southern Brazil, the family Ariidae is represented by the four valid species of the genus Genidens: G. barbus, G. genidens, G. machadoi and G. planifrons. Currently, three of these species have been recorded in lagoon-estuarine regions (G. barbus, G. genidens and G. planifrons), while G. machadoi has only been registered in marine environments. This paper presents the first record of G. machadoi in the Tramandaí Lagoon, in the northern coast of Rio Grande do Sul. From 2007 to 2011, the capture of 63 specimens of G. machadoi was recorded during the artisanal fishery inside the lagoon. The caught individuals had a mean total length of 460 mm (SD = 53.1 mm, mode = 460 mm; n = 63). Nineteen specimens (30.2%) were sexed, including five males and 14 females. Among the females, 11 were mature (78.6%) and the smallest mature individual was 422 mm in total length. These records represent the first confirmed evidence of the presence of the species in internal waters across its entire geographical range. The data gathered also suggest that G. machadoi uses the Tramandaí River Basin during the breeding season for spawning and egg incubation. Nevertheless, a more detailed study on the reproductive biology and life-history of this poorly known species is clearly needed. In addition, a better knowledge of the artisanal fisheries statistics is essential for the establishment of a sustainable management plan for the fisheries resources in the region.

Key words: Artisanal fisheries, reproductive biology, Tramandaí River Basin, Western South Atlantic.