The Tocantins–Araguaia basin is one of South America’s largest river systems, across three Brazilian states (Maranhão, Tocantins, and Pará), within the Legal Amazon region. Despite draining extensive Cerrado savanna and rainforest ecosystems, it has suffered significant degradation, notably in the past 40 years. Human activities, including agricultural expansion, deforestation, and the introduction of non-native species, have worsened the environmental damage, which is alarming since many residents and villages along the middle Tocantins River rely on it for water supply, recreation, and fishing. This study assessed the concentration of potentially toxic and essential elements in water samples from four sampling sites distributed along the middle Tocantins River. The monitoring occurred throughout 2023, involving the measurement of parameters both on-site and in the laboratory. Water quality and its health implications were evaluated using the Weighted Arithmetic Water Quality Index (WAWQI), the Water Quality Index (WQI), and the health risk assessment index. The levels of aluminum, copper, iron, magnesium, and selenium exceeded legal standards. Seasonal fluctuations indicate a complex dynamic influenced by climatic or seasonal factors, with February showing the highest values. Site P1, located in urban areas, exhibited elevated mean concentrations for conductivity, total dissolved solids (TDS), and chlorophyll, indicating the need for continuous monitoring. The nitrogen concentrations at P1 raise concerns regarding drinking water quality, which is a concern for the region’s residents who use untreated river water. Despite seasonal variations in element concentrations, the overall WAWQI categorized all sections as “Excellent,” and the WQI rated as “Good.” Human health risk assessments detected no risks, but continuous monitoring and interventions are crucial for sustained water quality improvement.

A piscicultura é uma solução para o problema da falta de recursos naturais e de alimentos. A prática da piscicultura como complemento do abastecimento alimentar às pessoas tem sido aplicada há anos com o seu desenvolvimento gradual e pela necessidade básica de alimentação. Faça ponto de vista dos procedimentos técnicos adotados, é possível classificar uma pesquisa como uma bibliografia documental com coleta de dados em fontes primárias e secundárias. Os dados foram coletados na Agência Estadual de Pesquisa e Extensão Agropecuária do Maranhão (AGERP) e Agência Estadual de Defesa Agropecuária do Maranhão (AGED). Entre as espécies cultivadas no estado do Maranhão, oito são espécies nativas, como tambaqui, pirarucu, piraíba, pirarara, pacu, dourado, surubim e tucunaré.A espécie que mais se destacou na produção foi o Tambaqui Colossoma macropomum . De acordo com os resultados da pesquisa, 71% dos peixes enviados para outros estados abastecem o Pará. Em relação às cidades que exportam pescado do Maranhão, 32% da população é de Senador La Rocque. Isso garante o desejo da comunidade em atender ao manejo dos recursos naturais e, consequentemente, à reprodução cultural, mantendo uma diversidade socioambiental dos municípios maranhenses dos produtores de peixes.

The aim of this study was to characterize the fish species Triportheus angulatus, Psectrogaster amazonica and Pellona castelnaeana from the middle Tocantins River. Samples were collected from stretches of the Tocantins River, such as Cacauzinho and Beira Rio. Statistical program was used to evaluate seven variables from the three species under study, which were then classified according to their degree of correlation. According to Pearson's correlation analysis, the variables were significantly associated with the characteristics of the three species examined. The averages of the variables studied were highest for Pellona castelnaeana, and lower for Psectrogaster amazonica and Triportheus angulatus. Morphometric comparisons between males and females revealed statistically significant differences (p < 0.05) in total length and body depth, indicating potential sexual dimorphism related to ecological or reproductive roles. The condition factor (K) ranged from 1.28 to 1.65, reflecting a generally good nutritional status among individuals. Future studies focusing on the sex and age of fish are necessary to analyze how regional anthropogenic problems have influenced the morphometric characteristics of these species and to identify the factors that contribute to the decline in fish quality. These results could support future local and regional conservation efforts, considering that fishing in the region is economically and culturally important.

O rio Tocantins é essencial para o sustento da população maranhense, porém, apesar de sua importância, a região enfrenta problemas de degradação ambiental pelo crescimento urbano acelerado, como desmatamento de encostas, exploração intensa de recursos pesqueiros, poluição do ar e água, assoreamento, dragagem e falta de saneamento. Objetivou-se investigar a percepção ambiental dos ribeirinhos quanto à qualidade da água do médio rio Tocantins através da aplicação de questionários estruturados. A pesquisa foi realizada entre os meses de agosto e dezembro de 2023, contando com um universo amostral de 50 entrevistados. Ainda, foi utilizada uma abordagem multimétodo para a integração de dados quantitativos e qualitativos. A população atingida foi composta por famílias ribeirinhas distribuídas entre quatro pontos de aplicação de questionário ao longo do médio rio Tocantins (P1: Beira Rio – zona urbana, P2: povoado Bananal, P3: povoado Embiral e P4: povoado Cidelândia). Percebe-se que a (88%) dos ribeirinhos no estudo residem no local há mais de 10 anos. Ainda, 34% consomem e comercializam peixes nativos, 62% usam apenas para consumo próprio e 4% não consomem. Ademais, 84% dos participantes afirmam não possuir rede de esgoto nas suas residências. Evidenciando a importância dos recursos pesqueiros e a água do rio para essa população.

The Tocantins River is crucial for the sustenance of the population in Maranhão; however, despite its significance, the region grapples with environmental degradation due to rapid urban growth. Issues such as deforestation of slopes, intense exploitation of fishery resources, air and water pollution, siltation, dredging, and lack of sanitation contribute to this concern. The study aimed to investigate the environmental perception of riverside dwellers regarding the water quality in the middle Tocantins River through structured questionnaire surveys. Conducted between August and December 2023, the research involved 50 respondents, employing a multimethod approach to integrate quantitative and qualitative data. The affected population comprised riverside families in four questionnaire application points along the middle Tocantins River (P1: Beira Rio – urban area, P2: Bananal village, P3: Embiral village, and P4: Cidelândia village). Notably, 88% of the participants had resided in the area for over 10 years. Additionally, 34% consumed and traded native fish, 62% used them solely for personal consumption, and 4% did not consume them. Furthermore, 84% of participants reported a lack of sewage systems in their residences, underscoring the importance of fishery resources and river water for this population.

This study investigates the length–weight relationship, growth patterns, and population structure of Prochilodus nigricans in a tropical river environment, providing biometric information relevant to ecological studies, fisheries assessment, and conservation planning. A total of 139 individuals were sampled across rainy and dry seasons, and biometric variables (BD—Body Depth, TL—Total Length, SL—Standard Length, TW—Total Weight, and GW—Gonad Weight) were compared using descriptive statistics and regression analyses. Significant differences in biometric parameters were observed between seasons and sexes. Among the sampled individuals, body depth, standard length, total length, and total weight were significantly higher during the rainy season for both sexes; however, these differences should be interpreted with caution because different gill-net mesh sizes were used between hydrological periods. Gonad weight and gonadosomatic index (GSI) differed significantly between males and females in both seasons. A significant overall effect of season was detected for gonad weight, although pairwise seasonal differences were observed only in males, whereas no significant seasonal effect was detected for GSI. Length–weight relationships indicated isometric growth in both sexes. These results provide baseline biometric information useful for future ecological studies and complementary fisheries assessments of P. nigricans in the Tocantins–Araguaia Basin.