Migration and brackish environment use of Prochilodus lineatus (Characiformes: Prochilodontidae) inferred by Sr:Ca ratio transects of otolith

Abstract

The streaked prochilod, Prochilodus lineatus, represents the most important fishery in the La Plata Basin (South America). Our objective was to analyze brackish environment use by the streaked prochilod captured from Paraná and Uruguay rivers. To accomplish this, lapillus otolith sections were analyzed for Sr:Ca with laser ablation-inductively coupled plasma-mass spectrometry (LA ICP-MS) to infer habitat use of fish. To the interpretation of transects, a threshold that represents the transition between freshwater and brackish environments was calculated using the Sr:Ca ratio of the otolith edge of specimens captured in the first section of the La Plata Estuary (salinity ≥ 0.5 PSU). The percentage of fish using the estuary was higher in the Paraná (37%) than the Uruguay River (5%). Change-point analysis showed that fish entered the estuary between 1 and 3 times throughout life at a wide range of ages (0-15 years). These incursions had no obvious periodicity. This information should be integrated into future management actions, which should also be specific to each area since migration patterns differ between the major rivers of the basin.Keywords: Connectivity, Freshwater resident, Laser ablation, River migration, Streaked prochilod.El sábalo, Prochilodus lineatus, representa la pesquería más importante en la Cuenca del Río de la Plata (Sudamérica). Nuestro objetivo fue analizar el uso del hábitat estuarino del sábalo proveniente de los ríos Uruguay y Paraná. Para esto, se analizó la relación Sr:Ca en secciones de otolitos lapilli por ablación láser acoplada a espectrometría de masas con fuente de plasma de acoplamiento inductivo (LA ICP-MS) para inferir el uso de hábitat. Para interpretar las transectas, un umbral que representa la transición entre los ambientes de agua dulce y estuarino, fue calculado usando la relación Sr:Ca del borde del otolito de especímenes capturados en la primera sección del estuario del Plata (salinidad ≥0.5 UPS). El porcentaje de peces que usaron el estuario fue más elevado para el Paraná (37%) en relación al Uruguay (5%). El análisis de cambio puntual mostro que los individuos ingresan al estuario entre 1 a 3 veces a lo largo de la vida en un amplio rango de edades (0-15 años). Las incursiones no mostraron una periodicidad notoria. Esta información debería integrarse a futuras acciones de manejo que deberían ser específicas para cada área considerando los patrones de migración que difieren entre los grandes ríos de la Cuenca.Palabras clave: Ablación laser, Agua dulce residente, Conectividad, Migración de rio, Sábalo.

Estimating contributions from nursery areas to fish stocks in freshwater systems using otolith fingerprints: The case of the streaked prochilod in the La Plata Basin (South America)

“…Estimates of stock composition showed that the degree of mixing was higher for adult fish (2014) compared with the subadults (2012), considering the estimations made with MLE and MCL (Figure ). Avigliano, Pisonero, et al () reported that between 5% and 37% of the fish caught in the Uruguay and Paraná rivers use the estuary once in their lives, migrating at least 1,000 km from the capture areas (next to nursery areas here studied). These large displacements were observed in individuals older than 3 years (Avigliano, Pisonero, et al, ).…”

“…Avigliano, Pisonero, et al () reported that between 5% and 37% of the fish caught in the Uruguay and Paraná rivers use the estuary once in their lives, migrating at least 1,000 km from the capture areas (next to nursery areas here studied). These large displacements were observed in individuals older than 3 years (Avigliano, Pisonero, et al, ). Other authors indicated the dominance of specimens between <1 and 3 years in some environments such as streams, associated floodplains, and lagoons, whereas older specimens (4 or 5 years and older) were dominant in the main course of Paraná (Sverlij et al, ).…”

“…The age‐2 fish correspond to subadult specimens and the age‐4 fish to adults of reproductive age (Sverlij et al, ). Sample sizes close to 30 were used for each year and site because in previous studies that amount was enough to estimate the proportion of “brackish–freshwater migratory/freshwater migratory” individuals in the Uruguay and Paraná rivers (Avigliano, Pisonero, et al, ).…”

“…Otolith preparation and trace element analysis were performed according to Avigliano, Pisonero, et al (). Left otoliths were weighed using a Sartorius AG ED 2242 (Göttingen, Germany) analytical balance, decontaminated three times with 2% HNO 3 (Merck KGaA, Garmstadt, Germany; Arslan & Secor, ), rinsed five times with Milli‐Q water (resistivity of 18.2 mΩ/cm), and dried overnight in a laminar flow hood.…”

“…The reproductive cycle of this species is correlated with the natural flood pulse regime, with migrations upstream and spawning in open river waters coupled to the flooding periods, as a mechanism of dispersion of eggs (Agostinho, Gomes, Veríssimo, & Okada, ; Baigún et al, ; Gubiani, Gomes, Agostinho, & Okada, ; Sverlij, Espinach Ros, & Ortí, ). Several works reported that the streaked prochilods migrate over 1,000 km to feed and reproduce (Avigliano, Pisonero, Dománico, Sánchez, & Volpedo, ; Bonetto, Canon Veron, & Roldán, ; Delfino & Baigun, ; Espinach Ros, Sverlij, Amestoy, & Spinetti, ). However, as the flood pulses are not regular, mass spawning and recruitment do not occur every year (Sverlij et al, ).…”