INTRODUCTION
The marine catfish Genidens barbus (Lacépède, 1803) (Siluriformes: Ariidae) is an anadromous species inhabiting estuaries and the marine continental shelf from Bahía, in Brazil, to San Blas Bay, in Argentina (17°00′S–40°32′S) (López & Bellisio, Reference López and Bellisio1965). It is considered as one of the most important fish resources in Argentina, Brazil and Uruguay (Velasco et al., Reference Velasco, Reis and Vieira2007; Silva Junior et al., Reference Silva Junior, Carvalho and Vianna2013). This species can live as long as 36 years, attaining a length of 120 cm, and reaches its maturity at the size of 40 cm (over seven or eight years old) (Velasco et al., Reference Velasco, Reis and Vieira2007). Adult inhabitants of the sea ascend rivers and estuaries during the months of September to December for reproductive purposes (Velasco & Reis, Reference Velasco and Reis2004; Velasco et al., Reference Velasco, Reis and Vieira2007) moving up to 500 km inland in Paraná River (freshwater environments) (Liotta, Reference Liotta2005). After females spawn in these areas, males return to the estuarine portion of the lagoon, carrying the eggs in the oropharyngeal cavity (Velasco & Reis, Reference Velasco and Reis2004). Cappato & Yanosky (Reference Cappato and Yanosky2009) classified the species as vulnerable due to its complex life cycle (low fecundity, oral incubation), its restricted distribution in fresh or estuarine waters during the reproductive period, the unknown environments that it inhabits afterwards and the critical harvesting rate of this species in fisheries.
In Argentina and Uruguay (South America), the known migration corridor was restricted to the De la Plata and Paraná Guazú Rivers (Figure 1) (Liotta, Reference Liotta2005; Cappato & Yanosky, Reference Cappato and Yanosky2009). In this article, we report for the first time the presence of G. barbus in three great rivers of the Paraná River Delta.
New records and migratory corridors of Genidens barbus in Paraná River Delta (Argentina). Red line represents the known reproductive migration corridor (Liotta, Reference Liotta2005); green line represents the new proposed migration corridor; green points represent new records.
MATERIALS AND METHODS
The Paraná River Delta (Argentina and Uruguay) discharges into the De la Plata River estuary (30,362 km2) at an average flow of 23,000 m3/s towards the Atlantic Ocean. The most important rivers in the Paraná River Delta are the Paraná Guazú, Sauce and the Uruguay Rivers (Figure 1). The conductivity in these rivers ranges from 40 to 173 µS m−1 (north–south) and the maximum depth ranges between 5 and 33 m (Guerrero et al., Reference Guerrero, Piola, Molinari and Osiroff2010; Avigliano et al., Reference Avigliano, Riaños Martinez and Volpedo2014).
Fish were collected with longlines on November 4 2014 in Sauce (N = 2), Paraná Bravo (N = 1) and the Uruguay Rivers (N = 1) (Paraná River Delta, Argentina) at a depth ranging from 10 to 33 m (Figure 1). The fish species were determined according to the diagnosis proposed by Marceniuk (Reference Marceniuk2005) and Marceniuk & Menezes (Reference Marceniuk and Menezes2007).
According to these authors, the following characteristics should be observed in each specimen: (1) lateral processes of urohyal short, (2) posterior portion of second basibranchial short, (3) posteroventral portion of opercle little pronounced posteriorly, (4) dorsal process of pharyngeal tooth plate and (5) the maxillary barbels clearer and sharper sideline.
Finally, the specimens were deposited as voucher specimens in the ichthyological collection of the Universidad de Buenos Aires (COLV/Fish-UBA).
RESULTS
A total of four adult fish (females with oocytes in an advanced stage of development) were collected (Figure 2). The data and the voucher numbers of the specimens are given in Table 1. These represent the first record of Genidens barbus in the Paraná Guazú, Sauce and Uruguay Rivers (Figure 1) (Paraná River Delta, Argentina).
Genidens barbus collected in Paraná River Delta (Buenos Aires province, Argentina). Scale bar = 6 cm.
New water body and data of the specimens of Genidens barbus collected in the Parana River Delta.
TW = total weight; TL = total length.
DISCUSSION
The catfish Genidens barbus is a commercially important resource in various commercial and artisanal fisheries operating in Argentina, Brazil and Uruguay (Velasco et al., Reference Velasco, Reis and Vieira2007; Silva Junior et al., Reference Silva Junior, Carvalho and Vianna2013). The largest volume of catches occurs in deep natural channels and wells of the Río de la Plata and Paraná Guazú between depths of 10 and 35 m (Avigliano, Reference Avigliano2014). These channel systems extend along the Rivers Paraná Bravo, Sauce and Uruguay, connecting them all together; this could provide a migration corridor, which would explain the reported catches in this work. On the other hand, catches that have been observed by artisanal and recreational fishermen in previous years (2010–2014) (per. comm.) indicate that the species uses these systems frequently. These new records could represent an extension of the reproductive migratory corridor of the species in the Paraná River Delta.
The information reported in this research is an important tool to be used in policy management, conservation and monitoring for the sustainable use of this resource throughout the region. A monitoring program should be introduced to the extension of the migratory corridor, where catches are considered rare or scarce, to update information and to set the basis for sustainable use and conservation management policies.
ACKNOWLEDGEMENTS
The authors are indebted to CONICET (PIP 112-20120100543CO), ANPCyT (PIP 2010-1372) and Universidad de Buenos Aires (UBACYT 20620110100007). We also thank Dr N.F. Schenone, an English speaker, for providing writing assistance that lead to the clarity and fluency of the English language, and the anonymous reviewers for their helpful comments on the manuscript.
