Long-term monitoring of potamodromous migratory fish larvae in an undammed river

Abstract

Freshwater fish reproduce annually in environments that provide favourable conditions for spawning and larval survival and growth. Thus, the aims of this study were to use long-term larval density data to evaluate the temporal distribution of the dourado Salminus brasiliensis, its habitat use for larval development and the effects of environmental variables on reproduction. S. brasiliensis larvae were mainly recorded in October and January in the Ivinheima River, and higher densities of larvae, primarily in the preflexion and flexion stages, were captured in the river and backwater biotopes. Water level, dissolved oxygen and temperature were the primary variables affecting the density of larvae, and this species can migrate over 200km to reproduce in the Ivinheima River and its tributaries. Therefore, S. brasiliensis is reproducing annually, indicating favourable local conditions for migration and spawning, and exhibits differential use of biotopes for reproduction, including rivers and backwaters (spawning) and lagoons (refuge and growth). Therefore, considering that the dourado is a key species for conservation, ensuring its reproductive success means maintaining a balanced ecological structure.

Arms as areas for larval development of migratory fish species in a Neotropical reservoir and the influence of rainfall over abundances

“…It is likely that these species migrate to the upper reaches of the There is a lack of information regarding the drift distances necessary for the offspring of Neotropical migratory fish to be successfully achieved. Rosa et al (2020), based on the duration of the development larval stages and river flow, verified that S. brasiliensis spawned 96 km upstream from the sites where the larval specimens were caught in the Ivinheima River (a tributary of the Paraná River, Brazil).…”

“…Rosa et al . (2020), based on the duration of the development larval stages and river flow, verified that S. brasiliensis spawned 96 km upstream from the sites where the larval specimens were caught in the Ivinheima River (a tributary of the Paraná River, Brazil). These authors inferred that PF larvae could be found 122 km downstream from the site of spawning.…”

“…Species such as B. orbignianus and Pseudoplatystoma reticulatum are suitable for exogenous feeding (PF stage) with ca . 24 h (at temperature >25°C) (Andrade et al ., 2016; Reynalte‐Tataje et al ., 2004) and S. brasiliensis with 20 h after hatching (at 26.5°C) (Rosa et al ., 2020).…”

“…In addition, their flow characteristics allow the drift of eggs and larvae to development areas, downstream, in the arms. The importance of tributaries for the reproduction and maintenance of ichthyological diversity in regions impacted by dams is also described in Gogola et al (2010Gogola et al ( , 2013 and Rosa et al (2020).…”

Drifting in a free-flowing river: Distribution of fish eggs and larvae in a small tributary of a Neotropical reservoir

“…In rivers, numerous species spawn in the channel, where larvae drift with the flow toward nursery areas located downstream. Depending on the species [e.g., Salminus brasiliensis (Cuvier, 1816)], the larvae may be carried toward downstream reaches for dozens of kilometers (Rosa et al 2020). In this sense, spatial and temporal assessments of ichthyoplankton distribution are important to understand reproductive and recruitment dynamics in an ecosystem (e.g., Castro et al 2002, Henry & Suiberto 2014, Rosa et al 2020.…”