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1. The Amazon basin hosts the Earth's highest diversity of freshwater fish. Fish species have adapted to the basin's size and seasonal dynamics by displaying a broad range of migratory behaviour, but they are under increasing threats; however, no study to date has assessed threats and conservation of Amazonian migratory fishes. 2. Here, the available knowledge on the diversity of migratory behaviour in Amazonian fishes is synthesized, including the geographical scales at which they occur, their drivers and timing, and life stage at which they are performed. 3. Migratory fishes are integral components of Amazonian society. They contribute about 93% (range 77-99%) of the fisheries landings in the basin, amounting to -US$436 million annually. 4. These valuable fish populations are mainly threatened by growing trends of overexploitation, deforestation, climate change, and hydroelectric dam development. Most Amazonian migratory fish have key ecological roles as apex predators, ecological engineers, or seed-dispersal species. Reducing their population sizes could induce cascading effects with implications for ecosystem stability and associated services. 5. Conserving Amazonian migratory fishes requires a broad portfolio of research, management, and conservation actions, within an ecosystem-based management framework at the basin scale. This would require trans-frontier coordination and recognition of the crucial importance of freshwater ecosystems and their connectivity. 6. Existing areas where fishing is allowed could be coupled with a chain of freshwater protected areas. Management of commercial and subsistence species also needs fisheries activities to be monitored in the Amazonian cities and in the floodplain communities to allow assessments of the status of target species, and the identification of management units or stocks. Ensuring that existing and future fisheries management rules are effective implies the voluntary participation of fishers, which can be achieved by increasing the effectiveness and coverage of adaptive community-based management schemes.

WOS:000608479300001; International audience; Identifying fish spawning areas is of great ecological and conservation importance as fishes are suffering increasing threat levels from anthropogenic activities. However, to date very few studies have done so in the Amazon basin. In the Beni River located in the upper Madeira basin, fishers reported that a particular ecotone near the town of Rurrenabaque was a fish reproduction area. To test the importance of this zone as a spawning site, we conducted an ichthyoplankton survey during the month when reproduction is most likely to occur. The specific identification of larvae and eggs was made with a metabarcoding analysis. With this approach 13 different fish species of high importance for regional and local fisheries were identified, including the long-distance migratory gilded catfish (Brachyplatystoma rousseauxii), considered as endangered in the upper Madeira. Combining the development time of morula-gastrula egg stages with the integrated current velocity of the river, we identified a spawning area that ranges between the last gravel beaches close to Altamarani community and the San Miguel del Bala community on top of Suse strait, the last foothill of the Andes. This spawning area further extends upstream in the Madidi and Pilon Lajas protected areas and Tacana and T’simane indigenous communities, when considering eggs in final embryo stage. This portion of the Beni River, at the Andean foothills, is heavily impacted by anthropogenic activities, ranging from unmanaged fisheries to contamination coming from the extraction of fluvial aggregates, upstream gold mining, deforestation associated with a sugar cane mill, an existing downstream dam, and projected upstream dam projects. Some urgent solutions for the conservation of this already impacted area are proposed. Confirming fish spawning zones, although difficult, is crucial to inform the definition of priority areas for conservation and management measures, in particular when these sites host endangered species.

There is a high international demand for timber from the genus Dipteryx, or "shihuahuaco" as it is known in Peru. Developing tools that allow the identification and discrimination of Dipteryx species is therefore important for supporting management of natural populations and to underpin legal trade of its timber. The objective of this study was the molecular characterization of Dipteryx species in the Peruvian Amazonia. Two plastid regions (cpDNA: trnH-psbA and matK) were sequenced and 11 microsatellite markers (nDNA) were genotyped for 32 individuals identified as Dipteryx charapilla, D. micrantha morphotype 1 and D. micrantha morphotype 2. Using the concatenated sequences of the plastid genes, we identified ten haplotypes that were not shared between the species or between the D. micrantha morphotypes. Haplotypic diversity was greater in D. micrantha morphotype 2 and D. charapilla than in D. micrantha morphotype 1, which presented only one haplotype with a wide distribution in Peru. The microsatellites allowed the discrimination of the same three clades and identified diagnostic alleles for each clade. These results allowed us to demonstrate that the two morphotypes of D. micrantha are different at both the plastid and nuclear markers, which supports the existence of three genetically distinct species in Peru. This study provides information for the genetic discrimination of Dipteryx species and emphasises the importance of conserving the genetic variability of this genus in the Peruvian Amazonia.

Our study is located in northern Beni and aims to improve knowledge on regional landscape changes from the last 8600 years, based on pollen and charcoal analyses from a lacustrine sediment core from Lake Ginebra. Our results showed that gallery forest and lacustrine sediment were observed from 8645 until 3360 cal yr BP. After a change from a lacustrine to a swamp environment at 1700 cal yr BP, the Cerrados and the Mauritia swamp became installed 1000 years ago on our study site. The environmental changes we observed over the last 8600 years in the Ginebra record reinforce the evidence of a west–east climatic gradient with the persistence of rain forest throughout the Holocene on the western side and the presence of the Cerrados until the late Holocene on the eastern side. Moreover, the persistence of a wet forest in the early to mid-Holocene in southwestern Amazonia highlighted some local responses to the global trend that could be related to the distance from the Andes; while in the late Holocene, both an increase in insolation and strengthening of the South American summer monsoon system enabled the installation of a seasonal flooded savanna in northern Beni and of the rain forest in eastern Beni.

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. 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 Sr-87/Sr-86 along transverse sections of their otoliths (ear stones), using laser ablation multi-collector mass spectrometry (LA-MC-ICP-MS). 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 thousand kilometres within the Amazon basin, with transboundary displacements between at least Bolivia, Brazil, and Peru. Current and planned hydroelectric development in the Amazon basin will severely disrupt both migration and access to breeding grounds, ultimately affecting the recruitment and population dynamics of these apex predators. The conservation of B.platynemum is crucial for the stability of the Amazonian aquatic food webs. This requires building effective fish passage on the two existing Madeira dams and considering alternative options to the large-scale hydropower development in the Amazon basin.

The goliath catfish Brachyplatystoma rousseauxii has crucial economical and ecological functions in the Amazon basin. Although its life history characteristics have been studied in the Amazon, there is little information in the Madeira River basin, which holds genetically distinct populations and where dams were recently built. Using fish collected in Bolivia, Brazil and Peru, this study provides a validation of growth rings deposition and details the growth patterns of B. rousseauxii in the Madeira before the dams' construction. Age structure and growth parameters were determined from 497 otolith readings. The species exhibits two growth rings per year and sampled fish were between 0 and 16 years old. In the Brazilian portion of the basin, mainly young individuals below 5 years old were found, whereas older fish (> 5 years) were caught only in the Bolivian and Peruvian stretches, indicating that after migrating upstream to reproduce, adults remain in the headwaters of the Madeira River. Comparing with previous publications, B. rousseauxii had a slower growth and 20 cm lower maximum standard length in the Madeira River than in the Amazon River. This study provides a baseline for future evaluation of changes in population dynamics of the species following dams closure.

International audience; The aim of this study was to evaluate the variation in growth and survival in Pseudoplatystoma punctifer larvae from 1 to 26 days post fertilization (dpf). Four progenies, obtained by combining the eggs of a single female and a pool of sperm from four males, were raised in communal tanks. All families were grown in a recirculating water system and fed with artemia from 3 days post-fertilization, five times a day and every 3 hours from 7:30 to 19:30. The mean total length and differential viability were calculated for each family, and analyzed by ANOVA. The results showed that from 4 hours after hatching there is a high contribution of two families to the progeny which was maintained until the end of the follow-up period (1 to 26 dpf). This is a clear evidence of the importance of male contribution in the early life history of the progeny.; El objetivo de este estudio fue evaluar la variación de crecimiento y la supervivencia en larvas de doncella, Pseudoplatystoma punctifer de 1 a 26 días post fertilización (1-26 dpf), cultivadas en situación comunal. Se obtuvieron 04 progenies, las cuáles fueron obtenidas por la combinación de los óvulos de una hembra con un pool de esperma de cuatro machos. Todas las familias fueron cultivadas en un sistema de recirculación de agua y alimentadas con nauplios de artemia a partir de los 3 dpf cinco veces al día y cada 3 horas de 7:30 a 19:30. El promedio de longitud total, viabilidad diferencial y la diferencia máxima en tamaño fueron calculadas para cada familia en las tres etapas (1dpf, 5 dpf y 26 dpf) de muestreo y analizadas por ANOVA. Los resultados mostraron que a partir de las 4 horas después de la eclosión hay una alta contribución de dos familias en la progenie el cuál fue mantenido hasta el final del periodo de seguimiento (26 dpf). Esto es una evidencia directa de la importancia del macho en la historia de vida temprana de la progenie.

With around 15% of all described freshwater fish species in the world, the Amazon Basin is by far the most fish species-rich freshwater ecosystem on the planet. In this opinion paper, a rough evaluation is given on just how vulnerable Amazonian freshwater fishes are to ongoing climate change. And to argue that current anthropogenic threats through rapid expansion of human infrastructure and economic activities in the basin could be a far greater threat to fish communities than those anticipated by any future climate change. Conservation actions in the Amazon Basin should focus preferentially on reducing the impacts of present-day anthropogenic threats.

Con el 15% de todos los peces de agua dulce descritos en el mundo, la cuenca amazónica es el sistema de agua dulce más biodiverso del planeta. Hoy en día, los factores principales de degradación de los ecosistemas de agua dulce en la región amazónica son la rápida expansión de las infraestructuras y actividades económicas. Estas perturbaciones provocan importantes efectos negativos en las comunidades de peces y podrían verse amplificados por los impactos del cambio climático. Las pérdidas de hábitat originados por el cambio climático no deberían tener efectos sobre las tasas de extinción de la especies. Sin embargo, el estrés térmico y la limitación de oxígeno podrían provocar extinciones locales de ciertas especies y producir cambios progresivos en la estructura y composición de las comunidades actuales de peces. Las especies tolerantes al aumento de temperatura, como el Paiche, se expandirán mientras que las especies sensibles a este aumento se reducirán. Cabe destacar que hoy en día las acciones de conservación deben enfocarse en la reducción de los efectos de las amenazas antropogénicas en curso.