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Non-native fish (NNF) can threaten megadiverse aquatic ecosystems throughout the planet, but limited information is available for the Amazon Region. In this study we review NNF data in the Amazonian macroregion using spatiotemporal records on the occurrence and the richness of NNF from a collaborative network of 35 regional experts, establishing the Amazon NNF database (ANNF). The NNF species richness was analyzed by river basin and by country, as well as the policies for each geopolitical division for the Amazon. The analysis included six countries (Brazil, Peru, Bolivia, Ecuador, Venezuela, and Colombia), together comprising more than 80% of the Amazon Region. A total of 1314 NNF occurrence records were gathered. The first record of NNF in this region was in 1939 and there has been a marked increase in the last 20 years (2000–2020), during which 75% of the records were observed. The highest number of localities with NNF occurrence records was observed for Colombia, followed by Brazil and Bolivia. The NNF records include 9 orders, 17 families and 41 species. Most of the NNF species are also used in aquaculture (12 species) and in the aquarium trade (12 species). The most frequent NNF detected were Arapaima gigas, Poecilia reticulata and Oreochromis niloticus. The current data highlight that there are few documented cases on NNF in the Amazon, their negative impacts and management strategies adopted. The occurrence of NNF in the Amazon Region represents a threat to native biodiversity that has been increasing “silently” due to the difficulties of large-scale sampling and low number of NNF species reported when compared to other South American regions. The adoption of effective management measures by decision-makers is urgently needed and their enforcement needed to change this alarming trend and help protect the Amazon’s native fish diversity.

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Resumen.-Se estudiaron los hábitos alimenticios de la pescadilla real Macrodon ancylodon basado en 280 muestras en la costa de la provincia de Mar anhão, noreste de Brasil . La dieta mostró un predominio de peces, cru stáceos y ocasionalmente cefalópodos. Las dietas de los machos y hembras fueron similares y se encontraron diferencias en la proporción de presas entre los juveniles, subadultos y adultos. Durante la temporada de lluvias las presas fueron más diversas que en la temporada seca. En la estación seca M. ancylodon se alimenta más de Penaeidae (Penaeus sp. y Penaeus schmitti), Callinectes sp. y Engraulidae (Cetengraulis sp.). Se observó un aumento del espectro de alimentos en la temporada de lluvias, con presas de 5 especies de peces (Anchovia clupeoides, Cetengraulis edentulus, Macrodon ancylodon, Mugil curema y Sardinella brasiliensis), 3 especies de crustáceos (Penaeus schmitti, Parapenaeus politus y Callinectes sp.) y 2 cefalópodos (Loligo sp. y Loligo plei). Las diferencias en la ingestión de presas se encontraron durante el año, en la estación de lluvia, donde los individuos de esta especie presentaron mayores contenidos estomacales. El canibalismo se encontró con mayor intensidad para los peces maduros. Palabras clave: Pescadilla real, dieta, contenido del estómago, MaranhãoAbstract.-The feeding habits of Macrodon ancylodon were studied based on 280 specimens from the Maranhão coast, northeast Brazil. The diet showed a predominance of fishes, crustaceans and occasionally cephalopods. The diets of males and females were similar and difference was found in the proportion of prey items among juveniles, sub adults, and adults (P > 0.05). During rainy season the prey items were more diverse than dry season. In the dry season M. ancylodon feeds more Penaeidae (Penaeus sp. and Penaeus schmitti), Callinectes sp. and Engraulidae (Cetengraulis sp.). An increase of food spectrum was observed in rainy season, preyed upon 5 species of fish ( Anchovia clupeoides, Cetengraulis edentulus, Macrodon ancylodon, Mugil curema and Sardinella brasiliensis), 3 species of Crustacea (Penaeus sp., Penaeus schmitti, Parapenaeus politus, and Callinectes sp.) and 2 Cephalopoda (Loligo sp. and Loligo plei). Differences in the ingestion of prey items were found during the year, where in the rainy season this species presented larger stomach contents. Cannibalism was encountered more intensively for mature fish.

Bull sharks are a cosmopolitan shark species frequently found in shallow shelf ocean waters and, occasionally, in several tropical river systems around the world. Due to bull shark's capability to enter riverine systems, the documentation of its occurrence is essential for future fisheries inspections and studies. In this way, this study aims to report the presence of a medium sized specimen of C. leucas in an equatorial river system. The specimen was caught by fishermen at Mearim River, located in Northern Brazil and well known for the occurrence of tidal bores during the highest spring tides of the dry season. The event coincided with the occurrence of one of the strongest spring tides of 2015. The captured female specimen measured approximately 1300 mm and weighted 35 kg. The occurrence of this species was not known in this river basin until now. We recommend and support future ichthyologic studies in the Mearim River basin in order to provide data for the delimitation of the territory used by C. leucas in Maranhão State, specially looking into its age, growth, diet, spatial, and temporal movement patterns in this area.

The Munim River basin is one of the main river drainages of the Hydrological unit Maranhão, but there are few published studies which focus on ichthyological surveys and taxonomic work within this basin. The present study aims to provide a fish species inventory of the Mata da Itamacaoca, one of the few urban protected areas from the upper Munim River basin, comparing the ichthyofauna with other lists by conducted at the upper Munim River basin. A total of 42 collection expeditions were conducted, the sampling was conducted at five collecting sites distributed within the boundaries of Mata de Itamacaoca, upper Munim River basin. Diversity indices were calculated and generalised linear models (GLMs) were employed to assess differences in species richness, diversity and evenness depending on season and location in relation to the reservoir dam wall. In order to visualize fish community differences, non-metric multidimensional scaling (nMDS) and a one-way PERMANOVA was used to understand whether factors of site, season and location to the dam wall had an effect on fish community compositions. A total of six orders, 13 families, and 23 fish species were found, and the order with the highest species richness, considering all reaches, was Characiformes followed by Cichliformes. The most abundant species was Nannostomus beckfordi, while Pimelodella parnahybae and Hoplerythrinus unitaeniatus were the rarer species sampled. There were no alien invasive species collected within the study area. Species richness was significantly higher below the dam wall, but there were no other significant differences in diversity indices with regards to season or location. Fish community composition was significantly different above and below the dam wall and was significantly affected by sampling site. Season did not have an effect on fish community. This study corroborates other studies conducted in the Unidade Hidrológica Maranhão sensu Hubbert and Renno (2006), that the ichthyofaunal composition and taxonomy of species within this region face major data deficits, anthropogenic impacts, this study may be a baseline for comparing similar environments throughout the region.