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Avec plus de 2 500 espèces actuellement répertoriées, la faune des poissons de l'Amazone représente plus de 15 % de l'ensemble des espèces de poissons d'eau douce décrites au monde. De nouvelles espèces sont décrites chaque année. La faune de poissons n'est pas seulement riche en espèces, mais montre également une diversité exceptionnelle de formes et de stratégies écologiques au regard des autres cours d'eau de la planète. Les raisons de cette méga-biodiversité ont intrigué les naturalistes depuis le XIXe siècle et continuent de rendre perplexes les systématiciens, écologues et paléontologues contemporains.

International audience

Workshop Latinoamericano de Otolitos y Otras Estructuras Calcificadas, Buenos Aires, ARG, 28-/08/2019 - 30/08/2019

Workshop Latinoamericano de Otolitos y Otras Estructuras Calcificadas, Buenos Aires, ARG, 28-/08/2019 - 30/08/2019

International audience; To study the effect of resource availability on the trophic niche width of fishes in the Bolivian Amazonbasin, we compared isotopic niche widths (as a surrogate for trophic niche) of three fish species(Acestrorhynchus altus, Hoplias malabaricus and Pygocentrus nattereri) in a gradient of prey availability.We sampled fishes in lakes located in the floodplain of the rivers Blanco (low prey availability), Iténez(intermediate prey availability) and San Martín (high prey availability), analyzed them for ratios ofstable isotopes (δ13C and δ15N), and estimated the standard ellipse and isotopic niche width using theSIBER package in R. Acestrorhynchus altus behaved as an optimal forager, showing wider isotopic nichewhere prey were less abundant, and less wide isotopic niche in rivers with intermediate and high preyavailability. P. nattereri showed wider trophic niche at intermediate prey densities and H. malabaricusshowed no effect of prey availability on isotopic niche width. This indicates that, for these species,factors such as prey selectivity, water transparency, mouth size or feeding habits, may be more importantthan prey availability in determining trophic niche width.; Con el objetivo de estudiar el efecto de la disponibilidad de recursos sobre la amplitud del nicho tróficoen peces de la Amazonia boliviana, comparamos los nichos isotópicos (como sustituto del nicho trófico)de tres especies de peces (Acestrorhynchus altus, Hoplias malabaricus y Pygocentrus nattereri) en ungradiente de disponibilidad de presas. Tomamos muestras de peces en lagos localizados en la llanura deinundación de los ríos Blanco (baja disponibilidad de presas), Iténez (disponibilidad intermedia) y SanMartín (disponibilidad alta), analizamos los ratios de isótopos estables (δ13C and δ15N) y estimamos laselipses estándar y amplitud de nicho isotópico (área) empleando el paquete SIBER en R. Acestrorhynchusaltus se comportó como un forrajero óptimo, mostrando un nicho isotópico más amplio a menordisponibilidad de presas y un nicho más estrecho en los sitios con disponibilidad intermedia y alta.Pygocentrus nattereri mostró un nicho más amplio a densidades de presa intermedias, y no encontramosefecto de la disponibilidad de presas sobre la amplitud del nicho trófico de H. malabaricus. Esto indicaque, para estas dos especies, factores tales como la selectividad de presas, transparencia del agua, tamañode la boca y hábitos alimenticios, podrían ser más importantes que la disponibilidad de presas paradeterminar la amplitud del nicho trófico.

International audience; Strontium isotopes (87Sr/86Sr) were evaluated as a potential method for studying the geographical origin of populations and movements patterns of migratory fish from the La Plata Basin (Paraná, Uruguay and Bermejo Rivers and Río de la Plata Estuary, South America). Surface water samples were collected at 43 sites during austral summer and winter (2018) while, Surubí (Pseudoplatystoma corruscans), Patí (Luciopimelodus pati), dorado (Salminus brasiliensis) and sábalo (Prochilodus lineatus) fishes were collected at seven locations. Water 87Sr/86Sr ratio was analysed by MC‐ICP‐MS (N = 74) and otolith core‐to‐edge 87Sr/86Sr transects (N = 50) were measured by LAfs‐MC‐ICP‐MS. Several water bodies presented significantly different (p

Supplemental material, revised_version_Supplemental_material for Archaeological history of Middle Holocene environmental change from fish proxies at the Monte Castelo archaeological shell mound, Southwestern Amazonia by Gabriela Prestes-Carneiro, Philippe Béarez, Francisco Pugliese, Myrtle Pearl Shock, Carlos Augusto Zimpel, Marc Pouilly and Eduardo Góes Neves in The Holocene

The Amazon Basin is an unquestionable biodiversity hotspot, containing the highest freshwater biodiversity on earth and facing off a recent increase in anthropogenic threats. The current knowledge on the spatial distribution of the freshwater fish species is greatly deficient in this basin, preventing a comprehensive understanding of this hyper-diverse ecosystem as a whole. Filling this gap was the priority of a transnational collaborative project, i.e. the AmazonFish project - . Relying on the outputs of this project, we provide the most complete fish species distribution records covering the whole Amazon drainage. The database, including 2,406 validated freshwater native fish species, 232,936 georeferenced records, results from an extensive survey of species distribution including 590 different sources (e.g. published articles, grey literature, online biodiversity databases and scientific collections from museums and universities worldwide) and field expeditions conducted during the project. This database, delivered at both georeferenced localities (21,500 localities) and sub-drainages grains (144 units), represents a highly valuable source of information for further studies on freshwater fish biodiversity, biogeography and conservation.

Strontium isotopes (Sr-87/Sr-86) were evaluated as a potential method for studying the geographical origin of populations and movements patterns of migratory fish from the La Plata Basin (Parana, Uruguay and Bermejo Rivers and Rio de la Plata Estuary, South America). Surface water samples were collected at 43 sites during austral summer and winter (2018) while, Surubi (Pseudoplatystoma corruscans), Pati (Luciopimelodus pati),dorado (Salminus brasiliensis) and sabalo (Prochilodus lineatus) fishes were collected at seven locations. Water Sr-87/Sr-86 ratio was analysed by MC-ICP-MS (N= 74) and otolith core-to-edge Sr-87/Sr-86 transects (N= 50) were measured by LAfs-MC-ICP-MS. Several water bodies presented significantly different (p < 0.05) water Sr-87/Sr-86 values. A similar to 1:1 relationship was found between Sr-87/Sr-86 measured in edge otolith and water. Data provide novel perspectives about migratory behaviour for all species, such as potential cross-border migrations between countries of more than 1,000 km recorded forL. pati, S. brasiliensis and P. lineatus. These species seem to move between the Parana and Uruguay rivers, which imply using the delta or the estuary as a corridor between them. Discriminant analysis based on otolith core Sr-87/Sr-86 suggested that the four species studied originate in sub-basins different from those that were collected and revelled the presence of several potential spawning/nursery areas. The otolith Sr-87/Sr-86 profiles also suggested movements between different environments such as reservoirs, large plain rivers, mountain streams, floodplain valleys and estuaries. These results show the potential of Sr-87/Sr-86 as a tool for tracking the life history of fishes, and depict for the first time a complex use of the La Plata basin by the fishes, providing new information for management plans at the regional level.

Supplemental material, tracked_revised_Supplemental_material for Archaeological history of Middle Holocene environmental change from fish proxies at the Monte Castelo archaeological shell mound, Southwestern Amazonia by Prestes-Carneiro Gabriela, Béarez Philippe, Pugliese Francisco, Shock Myrtle Pearl, Zimpel Carlos Augusto, Pouilly Marc and Neves Eduardo Góes in The Holocene

Monte Castelo, an archeological shell mound located on the southwestern periphery of the Amazon basin, is an artificial forest island occupied from the Middle to late-Holocene, and it contains one of the longest, continuous sequences of human occupation anywhere in the basin. Analysis of fish remains investigates fluctuations in the fish communities that are markers of changes in the paleoenvironment. The 8112 taxonomically identified remains document diagnostic taxa that are drought-tolerant (armoured catfishes, swamp-eels and tiger fishes) and from swampy environments, indicating probable occupation during low-waters periods. The results from Monte Castelo contrasts with the use of shell mounds as refuges from high-water season floods, a dominant hypothesis. A considerable shift in the nature of the fish spectrum occurred around 4000 BP with increased diversity; the number of taxa jumps from 18 to 48. The Middle Holocene occupations, from 6000 to 4000 BP, reflect long-term stability in drought-tolerant taxa collaborating with paleoecological evidence of dryer conditions. The post 4000 BP introduction of small-sized cichlids and characins suggests an initial exploitation of flooded forests. Archeological fish remains corroborate paleoenvironmental records of increased precipitation between the Middle and Late-Holocene. The probable replacement of some savanna areas by forest vegetation, and the accompanying alteration of aquatic landscapes, is documented through the presence/absence of certain taxa in Monte Castelo's occupations. This suggests new economic strategies and the exploitation of new ecological niches, as the fish remains correspond to approximately 80% of the vertebrate fauna throughout the archeological sequence.

Bolivia y Brasil comparten una de las cuencas más atractivas y preservadas de la te-giuri amazônica: la cuenca del rio llénez o Guaporé, que escurre tanto sobre el lecho rocoso del Escudo Precámbrico Brasilefto como sobre las Hanuras del Beni. Estas influencias hacen que la cuenca del iténez tenga una elevada heterogeneidad de habitats, una fauna acuálica peculiar y un alto valor de conservation. Este patrimo­nio binacional posée un potencial importante para la conservación de la diversidad regional y cl dcsar rollo sostcniblc participativo de las comunidades locales. El libro contiene un resumen del conotimìento de la cuenca y sus recursos, generado en los últimos 10 anos por un equipo de investigadores bolivianos, brasilefios y de otras nacionalidades. Se presenta una descripeión del medio fisico, así como resultados relevantes sobre la biodiversidad acuática, con énfasis en algas, peces, reptiles y mamíferos. El aporte más notable del libro, adernas de la descripeión ecológica del ecosistema, son las lecciones aprendidas que surgieron de experiências locales sobre la élaboration participativa de herramientas para la gestion de los recursos hidrobiológicos. A Bolívia e o Brasil compartilham uma das bacias hidrográficas mais atrativas e preservadas da região amazônica: a bacia do Rio Iténez ou Guaporé. A combinação das influências do escudo pré-cambriano brasileiro e da planícies do Beni é uma das razões pela qual existem na região elevada heterogeneidade de habitats, fauna aquática peculiar e alto grau valor dc conservação. Eslc patrimônio binacional possui potencial significativo para a conservação da diversidade regional e desenvolvimento sustentável participativo das comunidades locais. O livro contém um resumo do conhecimento da bacia e seus recursos, gerado nos últimos dez anos por uma equipe de pesquisadores bolivianos, brasileiros e de outras nacionalidades. Apresentamos uma descrição do meio físico, bem como resultados relevantes da biodiversidade aquática, com ênfase em algas, peixes, répteis e mamíferos. A contribuição mais notável do livro, além da descrição ecológica do ecossistema, é a descrição das lições aprendidas que surgiram a partir de experiências locais sobre elaboração participativa de ferramentas para a gestão dos recursos aquáticos presentes nesta bacia.

International audience

Goldschmidt 2019, Barcelone, ESP, 18-/08/2019 - 23/08/2019

Workshop Latinoamericano de Otolitos y Otras Estructuras Calcificadas, Buenos Aires, ARG, 28-/08/2019 - 30/08/2019

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.

La cuenca del río Iténez es afectada por actividades antrópicas que aumentan los riesgos de contaminación por mercurio, como son la minería aurífera y la deforestación. Este artículo presenta los resultados de un diagnóstico de los niveles de mercurio en sólidos suspendidos del agua, peces y pobladores ribereños. El estudio fue realizado en 2007 en el río Iténez, colector de aguas procedentes de diferentes áreas degradadas, y en dos ríos que drenan una cuenca poco intervenida (ríos San Martín y Blanco). Las tasas de mercurio contenido en los sólidos arrastrados por los ríos aparecen bastante homogéneas en los diferentes sectores estudiados, a excepción de los arroyos que drenan la mina aurífera de San Simón (que presentan hasta 40 veces más mercurio que los demás). Existe una relación directa entre la cantidad de mercurio particular transportada por el río y su carga de sólidos. Sin embargo, aunque naturalmente de aguas claras, los ríos que presentan un impacto (mina o deforestación) presentan un nivel de mercurio similar a los ríos de aguas blancas. Las concentraciones de mercurio en los peces del río Iténez son superiores a las encontradas en los peces de los ríos poco intervenidos. Las especies comerciales, en general carnívoras, presentan las tasas de mercurio más altas, sin embargo pocos individuos sobrepasan el límite aceptable para el consumo humano propuesto por la OMS (0.5 µg.g-1)-Los niveles de mercurio en los pobladores ribereños se encuentran también por debajo de los límites de riesgo para la salud con un promedio de 2.98 µg.g-1 de cabello. Sin embargo, los niveles de mercurio encontrados en las comunidades situadas en la proximidad del río Iténez son mayores con relación a las comunidades de las zonas de referencia. En conclusión, se destaca que el río Iténez presenta concentraciones de mercurio en aguas, peces y poblaciones ribereñas más altas que lo que se espera en condiciones naturales, las cuales sin embargo aún no son críticas. La determinación de la velocidad de evolución de esa contaminación es recomendable para poder estimar cuales son los riesgos de alcanzar un nivel de concentración crítico y el tiempo en que se llegaría a ella. A bacía do rio Iténez* é afetada pelas atividades humanas que aumentam o risco de contaminaçãn por mercurio, como o garimpo e o desmatamento. Este artigo apresenta os resultados de urna avaliação diagnóstica dos níveis de mercurio nos sedimentos da água, peixes e moradores ribeirinhos. O estudo foi realizado em 2007 no rio Iténez, coletou-se água de diferentes áreas degradadas, e de dois ríos situados em urna bacía pouco interferida (ríos San Martín e Blanco). As taxas de mercurio contidas nos sedimentos transportados pelos ríos sao bastante uniformes nos diferentes setores estudados, com exceção para os córregos que drenam a mina de ouro de San Simon (que tém até 40 vezes mais mercurio do que os outros pontos). Existe urna relação direta entre a quantidade de mercurio particulado transportadas pelo rio e sua carga de sedimentos. No entanto, embora naturalmente ríos de águas claras que tém um impacto (mineração ou desmatamento) possuam um nivel similar de mercurio aos rios de água branca. As concentrações de mercurio nos peixes do rio Iténez sao mais elevadas do que aqueles encontrados em peixes de rios pouco explorados. As espécies comerciais, em geral carnívoras, apresentam as maiores taxas de mercurio, mas alguns individuos excedem o limite aceitável para consumo humano proposto pela OMS (0,5 pg.g-1). Os níveis de mercurio em moradores ribeirinhos também sao inferiores aos limites de risco para a saúde, com urna média de 2,98 µg.g-1 de cabelo. No entanto, os níveis encontrados nas comunidades localizadas junto ao rio Iténez tém altas concentrações de mercurio em relação às comunidades nas áreas em quesão. Em conclusao, destaca-se que o rio Iténez apresenta concentrares de mercurio na água, peixes e populações ribeirinhas mais elevadas do que o esperado em condições naturais. No entanto, atualmente, as concentrares encontradas nos compartimentos estudados nao sao críticas. A determinação da velocidade da evolução dessa contaminação é aconselhável para poder estimar quais serão os riscos de atingir um nivel crítico de concentrado a curto e prazo.* Iténez e denominado rio Guaporé no Brasil. The Iténez* basin is impacted by anthropogenic activities which are known to increase mercury contamination risk, such as gold mining and deforestation. This paper presents results of a diagnostic study about mercury levels in river sediments, fish and humans. The study was conducted in 2007 in the Iténez main river that drains waters from degraded areas, and in two other rivers (San Martín and Blanco), draining waters from lowly impacted regions. Mercury level in water sediments appeared similar in all the studied sectors, except in some streams situated near San Simón gold mine that presented until 40 time more mercury than the other rivers. A positive relationship existed between water mercury level and particular sediment fraction of the water. However, although they naturally presented clear waters, rivers impacted by deforestation or gold mining contained similar mercury level than white waters (with high sediment load). Fish mercury concentrations were higher in the Iténez river (impacted area) than in the two lowly impacted ones. Commercial fish species, generally camivores, showed the highest mercury level, however only few fishes presented higher concentrations than the WHO sanitary level (0.5µg.g-1). Hair mercury concentrations in riverside human communities, with an average of 2.98 µg.g-1, were also below the accepted health risk level. In spite of this, mercury levels were higher in humans living on the Iténez riverside than in the other communities. Water sediment, fish and human mercury concentrations were higher in the Iténez river, which is impacted by anthropogenic activities, than in natural, lowly impacted, rivers in the same region. Nevertheless, no critical levels were recorded. A follow-up of the evolution of mercury contamination is recommended in order to estímate the risk of reaching critical levels.* The Iténez river is known as Guaporé river in Brasil.

La distribución de los peces es influenciada por diferentes tipos de variables bióticas y abióticas que actúan a diferentes escalas espaciales y temporales, las cuales son vistas como una sucesión de filtros jerárquicos que determinan la composición y estructura de las comunidades de peces. El presente trabajo compara la composición de las comunidades de peces en ríos y lagunas de la cuenca del río Iténez. La riqueza y composición específica, abundancia y biomasa de las principales especies así como variables ambientales se cuantificaron en 40 sitios de pesca representativos de seis subcuencas del río Iténez en Bolivia (Blanco, Machupo, Itonamas, Paraguá, San Martín e Iténez), clasificados por el tipo de agua (turbias o transparentes) y de hábitat (río, bahía y laguna). Un total de 261 especies fueron capturadas, pertenecientes a 8 órdenes y 30 familias. Los Characiformes y Siluriformes dominaron las comunidades ícticas tanto en riqueza como en biomasa. Los resultados sobre la distribución de las especies soportan la idea de que la composición y abundancia de las especies está controlada por factores ambientales. Las diferencias entre aguas turbias y transparentes operan como un primer filtro a nivel de subcuencas. Se encontraron 52 especies exclusivas de los ríos de aguas turbias y 60 exclusivas de los de aguas transparentes. Al contrario, dentro de las subcuencas, las diferencias de composición entre los tipos de hábitat (río, laguna y bahía) no son muy claras. Siguiendo el modelo PTM propuesto por Rodríguez & Lewis (1997), existe una relación entre la transparencia del agua y la abundancia de los órdenes Characiformes y Gymnotiformes, no presentándose para los Siluriformes. Los resultados demuestran que los indicadores clásicos como la riqueza, la abundancia y la biomasa total no reflejan las diferencias de composición observadas. A distribuigao dos peixes é influenciada por diferentes tipos de variáveis bióticas e abióticas que atuam em diferentes escalas espaciais e temporais, as quais sao vistas como urna sucessão de filtros hierárquicos que determinam a composigao e estrutura das comunidades de peixes. O presente trabalho compara a composição das comunidades de peixes nos ríos e lagos da bacia do rio Iténez*. A riqueza e composição específica, abundancia e biomassa das principais espécies assim como as variáveis ambientais foram quantificadas em 40 sitios de pesca representativos de seis subbacias do rio Iténez na Bolivia (Blanco, Machupo, Itonamas, Paraguá, San Martín e Iténez), classificados por tipo de água (águas turvas ou transparentes) e tipo de hábitat (rio, baia e lago). Um total de 261 espécies foram capturadas, pertencentes a 8 ordens e 30 familias. Os Characiformes e Siluriformes dominaram as comunidades ícticas tanto em riqueza como em biomassa. Os resultados de distribuição das espécies suportam a idéia de que a composigáo e abundáncia das espécies sao controladas por fatores ambientais. As diferenças entre águas turvas e transparentes atuam como um primeiro filtro no nivel das sub-bacias. Identificou-se 52 espécies exclusivas dos ríos de águas brancas e 60 exclusivas de rios de águas transparentes. Ao contrario, dentro das sub-bacias as diferen§as de composição entre os tipos de hábitat (rio, laguna e baia) nao sao muito claras. Seguindo o modelo PTM proposto por Rodríguez & Lewis (1997), existe una relação entre transparencia da água e abundancia de ordens para os Characiformes e Gymnotiformes. Ao contrario, essa relação nao existe para os Siluriformes.* Iténez e denominado rio Guaporé no Brasil. Fish distribution is influenced by abiotic and biotic factors playing at different spatial and temporal scales which can be considered as a hierarchical succession of filters that determine the structure and composition of fish communities. The present work compares the composition of fish communities from lakes and rivers of the Iténez* basin. It interprets the differences in relation to the regional factor of water type (inter sub-basin scale) and the local factor of habitat type (intra sub-basin scale). Fish species richness, specific composition, abundance and biomass of the principal species were quantified in 40 fishing locations that represented six sub-basins of the Iténez river in Bolivia: Blanco, Machupo, Itonamas, Paraguá, San Martín and Iténez. Each location was classified according to water type (turbid or transparent waters) and habitat type (lake, river or creek). 261 species were captured, belonging to 8 orders and 30 families. Characiformes and Siluriformes dominated the fish community in richness, abundance and biomass. Species distribution data supported the hypothesis that fish community composition and species abundance are controlled by environmental factors. Water type operated as a first level filter at the sub-basin scale: 52 species were exclusive of turbid waters and 60 species of transparent waters. Conversely, composition differences between habitat types were not clear. Following the PTM model proposed by Rodríguez & Lewis (1997), a quantitative relation existed between water transparency and Characiformes and Gymnotiformes fishes. However, this relation was not significant for the Silurifomes. Our results demonstrated that classical indicators such as richness, total abundance and biomass were not responsible for these differences, which rather originated from changes in specific abundance and composition.* The Iténez river is known as Guaporé river in Brasil.

The aim of this study was to analyse the trophic ecology of speckled peacock bass Cichla temensis inhabiting two tributaries of the middle Negro River, the Araca River and the Demeni River. Using an analysis of stomach contents and stable isotope composition (N-15, C-13) of scales, we describe the diet and evaluate the trophic position of subadult and adult individuals. We then test whether diet shifts and trophic positions occurred among successive size classes and among sample locations. The stomach content analysis confirmed the piscivorous feeding habit of the species and showed that the speckled peacock bass preyed on a variety species belonging to different trophic guilds. The length of the ingested prey increased with the size of the speckled peacock bass. Diet composition and trophic position were not different among size classes. C-13 values yielded significant shifts among the size classes: larger individuals displayed higher C-13 values than smaller individuals. Trophic position varied between locations, with lowest values observed in fish from the Araca River. This study demonstrated that diet of C.temensis may vary according to the size of the fish, even at the subadult or adult stages, and according to the river/locality, even within a same basin. We then suggest that further studies take into account local availability of food resources to better explore C.temensis diet and tropic ecology.