Importance of dam-free stretches for fish reproduction: the last remnant in the Upper Paraná River

Abstract

Aim: This study uses the abundance of fish eggs and larvae to evaluate the importance of the main channel of the Paraná River and the adjacent areas of the floodplain, in the last dam-free stretch in the Brazilian territory, for the spawning and development of fish of different reproductive guilds, in order to obtain subsidies to assist in the management and conservation policies of this area, focusing on the maintenance of dam-free areas. Methods: Data were taken quarterly from August 2013 to May 2015, in 25 sites, grouped into three biotopes: main channel, tributaries and lagoons. Possible spatial variations in fish spawning and development as well as composition and structure of larvae were evaluated. Results: Higher densities of eggs were found in tributaries (Paracaí and Amambai rivers) and greater densities of larvae were observed in lagoons (Saraiva). Significant differences in composition and structure of larvae were detected only between sampling stations. As for taxonomic composition, 29 taxa were recorded, mostly non-migratory. However, long-distance migratory were also widely distributed, such as Brycon orbignyanus, Pseudoplatystoma corruscans, Prochilodus lineatus, Piaractus mesopotamicus and Rhaphiodon vulpinus, as well as invasive species Platanichthys platana and Hemiodus orthonops. In turn, Salminus brasiliensis presented low occurrence. Conclusions: This study evidenced that different species spawn in the region, mainly in tributaries, and their eggs and larvae are transported to the main channel of the Paraná River and adjacent lagoons, to complete their early development. The capture of larvae of important migratory species suggests that this environment still exhibits suitable conditions for their reproduction, mainly due to the presence of dam-free tributaries. Also, they emphasize the importance of the integrity of these environments for the maintenance of the regional fish fauna, and it is extremely important the monitoring of reproduction of the most endangered species, as well as of invasive species.

Damming and seasonality as modulators of fish community structure in a small tributary

“…Species that migrate long distances are often the most affected by barriers such as dams (Esguícero & Arcifa, ; Hoeinghaus et al, ). However, some studies have shown that species migrating long distances can maintain viable populations in lotic areas, upstream of dams or in dam‐free tributaries (Baumgartner, Nakatani, Gomes, Bialetzki, & Sanches, ; Makrakis et al, ; Nobile et al, ; Silva et al, ). Nowadays, most Brazilian reservoirs display only three large migratory species (Agostinho et al, ; Nobile et al, ), in contrast to the dozens found in the pristine environment, that occurred predamming.…”

Temporal changes in fish diversity in lotic and lentic environments along a reservoir cascade

“…When there are no lotic remnants between reservoirs built in series along a river (this varies according to the water level of the next reservoir in the cascade), the possibilities to compare lotic and lentic environments in a cascade are more limited. Nevertheless, a few studies have demonstrated fish diversity impacts in lotic stretches between dams in a reservoir cascade (Ferrareze, Casatti, & Nogueira, ; Ferrareze, Nogueira, et al., ; Miranda & Dembkowski, ; Miranda et al., ; Silva et al., ). Moreover, there are indications that lotic stretches associated with lentic environments are important for the maintenance of fish diversity (Agostinho et al., ; Marques et al., ; Miranda & Dembkowski, ; dos Santos et al., ).…”

Relationship of Freshwater Fish Recruitment With Distinct Reproductive Strategies and Flood Attributes: A Long-Term View in the Upper Paraná River Floodplain

“…The first rains act as a cue for the formation of schools and migrations upstream to search for the best environmental conditions for spawning (Vazzoler and Menezes, 1992;Cowx et al, 1998;Suzuki et al, 2004). The migratory fish usually spawn in the uppermost regions of the basin and use flooded area, dozens of kilometers downstream, as nurseries for their early stages of development (Nakatani et al, 2001;Wantzen and Junk, 2006;Silva et al, 2017;Rosa et al, 2018). For these species, long-lasting floods in the warmer season can maximize recruitment (Gomes and Agostinho, 1997;Oliveira et al, 2015), providing shelter and food for more extended periods.…”