Shedding light on the migratory patterns of the Amazonian goliath catfish, Brachyplatystoma platynemum, using otolith ⁸⁷Sr/⁸⁶Sr analyses

Abstract

1. In the Amazon, migratory catfishes of the genus Brachyplatystoma are apex predators that are important for fisheries and conservation. The life cycle of Brachyplatystoma platynemum Boulenger, 1898 is poorly known, although it has been hypothesized to be very similar to that of Brachyplatystoma rousseauxii Castelnau, 1855, which uses the entire length of the Amazon basin to complete its life cycle (from the Andes to the estuary). This study provides the first data on the migratory patterns of B. platynemum at the individual level using otolith microchemistry.2. In total, 94 individuals were sampled close to major breeding areas in the Amazon basin (78 fish from the middle and upper Madeira River and 14 fish from the upper Amazon), and their lifetime movements were assessed by measuring variations in 87 Sr/ 86 Sr along transverse sections of their otoliths (ear stones), using laser ablation multi-collector mass spectrometry (LA-MC-ICP-MS).3. The migrations of B. platynemum are not as extensive as those of B. rousseauxii, and do not involve natal homing. Furthermore, the estuary is not a nursery area, at least for fish hatched in the Madeira. Nevertheless, B. platynemum migrates several

Conservation of migratory fishes in the Amazon basin

“…The longest longitudinal migrations known in freshwater ecosystems are performed by a group of large‐bodied (1–3 m) goliath catfishes of the genus Brachyplatystoma (Barthem & Goulding, 1997; Barthem et al, 2017; Hauser, 2018; Hauser et al, 2019). One species, Brachyplatystoma rousseauxii , performs a trans‐Amazonian round‐trip migration of up ~12,000 km between its hatching areas in the Andean piedmont of Bolivia, Colombia, Ecuador, and Peru and its nursery in the lower Amazon and estuary in Brazil (Barthem & Goulding, 1997; Barthem et al, 2017).…”

“…Although most studies have been carried out in the heavily fragmented Paraná and Paraguay basins, they show that despite financial investments and engineering efforts in the construction of fish passes, these are largely ineffective in the re‐establishment of routes, free upstream and downstream movements of young and adults, and regional recruitment (Agostinho et al, 2007; Lira et al, 2017; Pompeu, Agostinho, & Pelicice, 2012). In the Amazon basin, otolith microchemistry analyses have provided clear evidence that fish passes in the recently constructed Jirau and Santo Antônio dams on the Madeira River do not currently permit upstream passage of sub‐adult B. rousseauxii returning from the lower Amazon estuary (Hauser, 2018) and prevent former movement of Brachyplatystom platynemum between the upstream and downstream reaches of the dams (Hauser et al, 2019).…”

Harnessing the potential for otolith microchemistry to foster the conservation of Amazonian fishes

“…Thus, with an adequate catalogue of values for a geographical region (assuming unique ratios for many sites within the region), it is possible to reconstruct fairly accurately the migratory life history of an individual. Isotope ratios for the geology of many drainages in the Amazon are available in the literature (Duponchelle et al, 2016; Hauser et al, 2019; for summaries, see Hegg, Giarrizzo, & Kennedy, 2015; Santos et al, 2015), which allows the study of species with very different migratory behaviours. For example, Sr isotope ratios have been used to study short‐distance migrants such as Arapaima spp.…”

First record of the mating behaviour of the spotted surubim Pseudoplatystoma corruscans in the Uruguay River

“…Nonetheless, basic and important aspects about their ecology remain poorly understood, especially the reproductive behaviour of large catfishes. Recently, some migratory patterns have been unravelled in the Amazon basin (Barthem et al ., 2017; Hauser et al ., 2019), but mating and spawning behaviours in the wild remain largely unreported for this group of fishes.…”