Lower Amazon Region Research Articles

USO DEL MARCADO INDIVIDUAL CONOCIDO EN LA INVESTIGACIÓN Y MONITOREO DE POBLACIONES DE TORTUGAS DE ÁGUA DULCE: PRUEBA DEL MÉTODO EN ESPECIES SUDAMERICANAS (TESTUDINES PODOCNEMIDIDAE)

The marking or tagging of turtles is a widely used to facilitate the monitoring of population demography, structure, and conservation of species. Even though they are used in many studies of turtle demography, the available methods are not very efficient, except for microchips (Passive Intergraded Transponder/PIT tags); however, the latter is too expensive to be used on a large scale. Here we present a viable, cost-effective tagging alternative that uses a durable plastic cattle tag and pin. Turtles in the genus Podocnemis were tagged in the Lower-Amazon region, west of the state of Pará, Amazon, Brazil. This method is highly recommended for future work on monitoring and population structure of large species of freshwater turtles. In addition to feasibility, it can be used in the form of citizen science, as the information can be obtained by laypeople and taken to researchers and conservationists.

Phytochemical prospection of extracts from the leaves of pata de vaca (Bauhinia forficata) from the Parintins region, Amazonas, Brazil

Phytochemistry stands out for the study of the active principles of metabolites synthesized by plants. Compounds in general have biological activities, capable of bringing benefits to humans. The Bauhinia forficata object of this study, popularly known as Pata de Vaca, native to Brazil. This species of tree is very common in the lower Amazon region, particularly around Parintins. Under laboratory conditions, organic n-hexane and acetic extracts from leaves of Pata de vaca (Bauhinia forficata) were subjected to preliminary chemical tests, where the classes of compounds investigated were alkaloids, tannins, saponins and flavonoids. As a result of the tests for the n-hexane extract, all three were negative and positive for saponins, while for the acetic extract, the four tests had positive results. Therefore, it is concluded that the species presents bioactive compounds, with the need for further studies.

Comparative analysis between mercury levels in fish tissues evaluated using direct mercury analyzer and inductively plasma-coupled mass spectrometer

Recent ecotoxicological studies have indicated mercury (Hg) contamination in aquatic ecosystems in the Amazon Basin. Although Hg contamination can be associated with small-scale gold mining, the soils of the Amazon region have naturally high Hg concentrations, and can be transported to aquatic ecosystems via deforestation and mining activities. Biomagnification of Hg can pose risks to the local human population; therefore, its concentration in fish tissues must be monitored consistently. Fast and sensitive Hg determination is required for continuously monitoring ecosystems impacted by mineral exploration. The direct mercury analyzer (DMA-80) is widely used for determining total Hg levels in tissue samples; it is fast and cost-effective, without requiring sample preparation. Here, we determined the sensitivity and specificity of Hg detection accomplished using DMA-80, and whether these results are reliable compared to those obtained using Inductively Coupled Plasma Mass Spectrometer (ICP-MS), which is the gold standard. We obtained 106 paired dried samples of muscle tissue from fish species occupying different trophic levels in the Lower Amazon region, and analyzed them using both equipment (DMA-80 and ICP-MS). The results obtained using DMA-80 had an overall Hg mean of 1.90 ± 0.18 mg/kg which was higher (p < 0.05) than the mean of those obtained using ICP-MS (1.55 ± 0.13 mg/kg). Linear regression analysis comparing the Hg levels obtained using both devices was within the 95% prediction interval, and a high coefficient of correlation showed agreement between the devices (r = 0.979; 0.069 to 0.986, 95% CI). Bland-Altman analysis showed that DMA-80 had a positive bias of 6.5% in relation to ICP-MS, which is more evident in samples with high Hg concentrations. DMA-80 was efficient in determining whether the Hg levels exceeded the maximum allowed levels required by the European Union, USA, and Brazil, showing a specificity and sensitivity of above 95%.

Evaluation of the degree of contamination of breast milk by organochlorine pesticides in the Lower Amazon region: a preliminary study

The main source of human exposure to organochlorines is through food, especially food with a high fat content, such as breast milk, which is critical for child hood development. Therefore, it is important to analyze milk and other biological matrices for organochlorine pesticides (OCPs), and then determine the source of the OCP contamination. The objective of this study was to evaluate the degree of contamination by OCP residues and their metabolites in breast milk samples from the municipalities of Mojuí dos Campos and Belterra-Pará, Brazil. The OCPs analyzed were dichlorodiphenyltrichloroethane (DDT) and its metabolites (o,p'-DDT, p,p'-DDT, o,p'-DDE, p,p'-DDE, o,p'-DDD, and p,p'-DDD), aldrin, endrin, dieldrin, hexachlorocyclohexanes (α-HCH, β-HCH, lindane (γ-HCH), and δ-HCH­­), endosulfan α and β, endosulfan sulfate, heptachlor, and heptachlor epoxide. These substances were analyzed in 22 breast milk samples using gas chromatography with an electron capture detector (GC-ECD). Seven were contaminated with p,p'-DDT and/or p,p'-DDE. The mean p,p'-DDT and p,p’-DDE content in the contaminated samples was 0.0022 and 0.0152 mg·kg-1 of milk, respectively. This contamination may have been due to the inadequate application of DDT until the end of the 1990s for the control of tropical diseases, including malaria. Despite being a preliminary study, the number of contaminated samples was significant, which suggests the need to expand this study to other environmental and biological matrices.

First Description of Acaricide Resistance in Populations of Rhipicephalus microplus Tick from the Lower Amazon, Brazil.

There is limited information on the resistance to acaricidal drugs of the cattle tick Rhipicephalus microplus in the Lower Amazon region. Thus, we aimed to determine the efficiency of three widely used acaricide products (Amitraz, Cypermethrin, and Deltamethrin) in the control of this tick species. The adult immersion test was used on engorged female ticks sampled on farms in the Lower Amazon region, Brazil. For the test, homogeneous batches of 10 engorged females were placed in Petri dishes and immersed in the tested acaricidal drugs, using four replicates of each acaricide and three replicates as a negative control, immersed in distilled water. The acaricides were diluted as recommended by the manufacturers, and the ticks were submerged for five minutes. Mortality of engorged females, production of eggs, and percentage of larval hatching were evaluated. Tick mortality was 2.5%, 7.5%, and 0% for Amitraz, Cypermethrin, and Deltamethrin, respectively. The percentage of larval hatching was 53.7% for Amitraz, 88.7% for Cypermethrin, and 80.0% for Deltamethrin. As recommended by the FAO, for the acaricide to be considered effective, it must have a control rate ≥95%. Among the tested acaricides, Amitraz showed an efficacy of 90.5%, Cypermethrin 10.4%, and Deltamethrin 26.6%. Ticks from the lower Amazon showed marked resistance to Cypermethrin and Deltamethrin and mild resistance to Amitraz. This is the first report of acaricidal resistance in the region.

Adherence to oral anticancer therapy of oncology patients attending the pharmaceutical office of a public hospital in the lower Amazon region.

Introduction:Oral anticancer therapy has the benefit of allowing cancer patients to carry out their treatment at home, without being inconvenienced or being at risk of nosocomial infection. However, non-adherence is a public health problem that contributes to the clinical decline of the patient and there are no studies submitted on the adherence of cancer patients to oral anti-anticancer agents in Santarém, PA.Objective:In view of this, the general objective of this work was to evaluate this oral medication adherence.MethodsThe methodology consisted of a cross-sectional documentary study with a quantitative approach of patients seen at the pharmaceutical office. The Morisky–Green test was used to analyse the degree of adherence and descriptive and inferential statistics were used (p < 0.05).Results:Patients’ adherence to antitumour therapy was not 100%, the majority belonging to females; men were the most adherent, showing adverse reactions to anti-anticancer agents (p = 0.0096); comorbidity (p = 0.0202) negatively impacted adherence.Conclusion:It is necessary to adopt new clinical procedures that can contribute to the management of these variables that prevent adherence, in order to improve the effectiveness of the treatment of these patients. There are circumstances that go beyond the aspects inherent to the patient, so it is also relevant to research the external factors that influence the individual’s behaviour, such as the duration of therapy and the consequences of the treatment in the patient’s routine.

The Legal Roundwood Market in the Amazon and Its Impact on Deforestation in the Region between 2009–2015

Brazil is one of the largest producers of tropical wood in the world. Much of this wood is extracted from the Amazon region, especially in the state of Pará. Despite empirical knowledge, there is little information in the literature about the selectivity of trade and how this production has been behaving in recent years. Is there any relationship between this legal timber trade and deforestation? In this work, we compile data reports from control agencies and analyze the dynamics of the legal timber market in the state of Pará between 2009 and 2015 in terms of species, volume, and monetary value. We also correlate changes in volume m−3 and value m−3 with deforestation increase in the same period and region. We find that only ten groups of species represent almost 50% of the total timber volume marketed in the State, mainly from the Massaranduba (Manilkara) group. According to our models, the supply of a species of wood on the market is defined by its monetary value and not by its availability or characteristics, which hinders the insertion of new species and increases selectivity. Since 2011 the volume of legally traded logs has been decreasing sharply. Traditional forest regions in the state already demonstrate depletion in forested areas. While others, such as the lower Amazon region, have been increasing production, showing that new forestry operations areas are being used for harvesting in the function of the lower availability in traditional areas. Our models show that the legal reduced impact logging timber volume has an inverse relationship with the deforestation increase. Otherwise, preference for a small group of timber types still predominates, which may lead local woods to the danger of extinction.

A PESCA ARTESANAL NA COMUNIDADE COSTA DO TAPARÁ (PA): SUBSÍDIOS PARA GESTÃO PESQUEIRA

Artisanal or small-scale fishing is one of the oldest extractive activities in the lower Amazon region, generating income and subsistence for a good part of the riverside population. In this sense, the objective of the research was to characterize the fishing activity and socioeconomic structure of artisanal fishermen in the Costa Tapará community, Santarém, Pará State. Data collection was carried out through interviews with semistructured forms to 82 fishermen out of a total of 302 registered fishermen, during the period from March to November 2019. Data analysis was performed using descriptive statistics. The results showed that the average age of the fishermen was 37.6 (81.7%) years (± 11.5), 70.7% had incomplete primary education and 91.5% had fishing as their main source of income. The fishing activity is presented as artisanal and on a small scale, practiced in small wooden rowing and/or motorized boats, employing multiplicity of equipment highlighting the reed, mesh, and net. July and August stood out as the best fishing season. The biggest problems identified in the community were socioenvironmental conflicts. Understanding how this community dynamic works will directly contribute to the development of management alternatives and regional fishing sector planning.

Optical Classification of Lower Amazon Waters Based on In Situ Data and Sentinel-3 Ocean and Land Color Instrument Imagery

Optical water types (OWTs) were identified from an in situ dataset of concomitant biogeochemical and optical parameters acquired in the Amazon River and its tributaries, in the Lower Amazon region, at different hydrological conditions from 2014 to 2017. A seasonal bio-optical characterization was performed. The k-means classification was applied to the in situ normalized reflectance spectra (rn(λ)), allowing the identification of four OWTs. An optical index method was also applied to the rn(λ) defining the thresholds of the OWTs. Next, level-3 Sentinel-3 Ocean and Land Color Instrument images representative of the seasonal discharge conditions were classified using the identified in situ OWTs as reference. The differences between Amazon River and clearwater tributary OWTs were dependent on the hydrological dynamics of the Amazon River, also showing a strong seasonal variability. Each OWT was associated with a specific bio-optical and biogeochemical environment assessed from the corresponding absorption coefficient values of colored dissolved organic matter (aCDOM) and particulate matter (ap), chlorophyll-a and suspended particulate matter (SPM) concentrations, and aCDOM/ap ratio. The rising water season presented a unique OWT with high SPM concentration and high relative contribution of ap to total absorption compared to the other OWTs. This bio-optical characterization of Lower Amazon River waters represents a first step for developing remote sensing inversion models adjusted to the optical complexity of this region.

LENGTH-WEIGHT RELATIONSHIP OF THE SIX MOST ABUNDANT FISH SPECIES IN PRAWN FISHERY SEMI-FIXED TRAP BYCATCHES IN THE LOWER AMAZON REGION (PARÁ, BRAZIL)

In this study, the length-weight relationships (LWR) were estimated for six fish species captured during prawn fishing in the Lower Amazon region (Pará, Brazil). Prawn fishing boosts the socioeconomic development of riverine communities and is a relevant activity as a source of income and subsistence in this region. In addition, we registered new LWRs for the species Ossancora punctata and Hypoptopoma elongatum. The samplings were performed in prawn catches monthly from February 2018 to January 2019, using a "matapi" which consists of a semiâ€"˜fixed trap that has a galvanized iron structure (2.5 m height by 2.0 m in length) and nylon mesh (1.40 x 1.60 mm mesh), and has two tapered openings to facilitate the entry and trapping of the prawn. The results show that 75% of the fish caught as prawn bycatches had not yet reached sexual maturity. Thus, it is clear that fisheries need to develop fishing gear that allow small fish to escape from the traps during the prawn fishery.

Hydrologic variability effects on catches of Prochilodus nigricans in the lower Amazon

Flooding events in large rivers, termed flood pulses, expand and contract habitat available for fish populations, affecting fish abundance and catches. Here, we investigated if river hydrologic variability affected catch of curimata (Prochilodus nigricans), a widely distributed and economically important fish species of the Amazon Basin. Using fish catch and fishing effort data for the lower Amazon region collected between 1993 and 2004, we performed an (i) analysis of covariance (ANCOVA) to understand the intra-annual relationship, and (ii) a cross-correlation function (CCF) to assess the inter-annual lag associated between river water levels and catches. We found that the intra-annual relationship between monthly river water levels and monthly catches of P. nigricans was negative, resulting in greater catches during lower river water levels and vice versa. We also found positive correlations with an inter-annual lag of 15-months between river water levels and catch, indicating that years with more extensive flooding lead to greater than normal catches of P. nigricans 15 months later. Increased flooding can be hypothesized to lead to increased survival and growth rates of P. nigricans. This dependency of catches of P. nigricans on river hydrological cycles underscores the threat posed by ongoing hydrological alterations to fish-related food and income security in the region. Further research is necessary to assess the extent to which such hydrological effects can impact multispecies fisheries catches in light of growing levels of fishing pressure.

Morphological and allometric variation due to percentage of cover in Eichhornia azurea (Swart) Kunth (Pontederiaceae)

Exploring the density-dependence theory is crucial to understanding how size patterns among individuals are established. This study tested if percent cover affects the morphological and allometric relationship variation of individuals of Eichhornia azurea (Swart) Kunth, an emergent perennial mat-forming macrophyte commonly found in the lower Amazon region. We predicted that (1) E. azurea found in sites with high percent coverage would have larger, thicker, heavier leaves and longer petioles than individuals found in sites with low percent coverage; (2) the percent coverage affects the allometric relationship between branch length and number of leaves. To test our predictions, we sampled sites with low and high E. azurea percent cover. Sampling occurred in Caxiuana Bay located in Caxiuana National Forest on the lower Amazon. The results supported our predictions, in which individuals of high percent cover sites had longer petioles, more leaves, thicker leaves and higher leaf mass per area. Individuals in low percent cover sites showed a positive relationship between branch length and number of leaves. These results indicate that E. azurea exhibits morphological and allometric plasticity in response to plant density which may help explain the success of E. azurea in a variety of habitats across South America.

Toxic and essential trace element concentrations in fish species in the Lower Amazon, Brazil

The Lower Amazon region (Western Pará, northern Brazil) is greatly affected by mining exploitations (particularly artisanal gold mines) and other industrial and intensive agricultural activities with potentially strong impacts on aquatic ecosystems. Although such impacts include contamination with various toxic elements, to date only the effects of Hg have been considered. In this study, toxic and trace element concentrations were determined in the flesh of 351 fish specimens, including detritivores (Acarí, Pterygoplichthys pardalis), omnivores (Piranha, Pygocentrus nattereri; Pirarucu, Arapaima sp.) and carnivores (Caparari, Pseudoplatystoma fasciatum; Tucunaré, Cichla ocellaris), during the dry and wet seasons in 2015 and 2016. The range of concentrations of toxic element residues were 2–238 μg/kg fresh weight for As, 1–77 μg/kg for Cd, 4–1922 μg/kg for Hg and 1–30 μg/kg for Pb. Only the maximum concentrations of Hg established in the Brazilian legislation for fish destined for human consumption (0.5 mg/kg) were exceeded (in 16% of carnivorous species). The large between-species and seasonal differences observed for all these toxic elements are probably related to the seasonal behaviour and dietary habits of the different fish species. By contrast, essential trace element concentrations were low and not related to seasonal or dietary factors, and the observed differences may be at least partly related to the metabolism of each species. The associations between Hg and the essential trace elements Se, Fe, Co and Mn deserve special attention, as these trace elements may play a role in Hg cycling and methylation and merit further evaluation with the aim of reducing Hg toxicity in aquatic environments.

Resistências dos Movimentos Sociais e ONGs frente ao Avanço do Agronegócio no Oeste da Amazônia Paraense

Este trabalho tem como objetivo analisar o papel dos movimentos sociais e organizações não governamentais (ONGs) frente ao avanço do agronegócio que se cristaliza no oeste do estado do Pará, região do Baixo Amazonas, no contexto da Geografia Agrária. Essa temática vem sendo muito debatida e enfrentada pelos movimentos sociais e ONGs no oeste paraense. A metodologia utilizada se deu por meio da revisão teórica conceitual e do trabalho de campo, com uso da técnica de entrevistas semiestruturadas com membros representantes de movimentos sociais e ONGs, bem como também registros de imagens do ambiente investigado. Nota-se que a partir da territorialização da agricultura capitalista e hegemônica houve mudanças das paisagens na região que metamorfoseou as relações socioespaciais e socioterritoriais. Nesse sentido, a implementação de sistemas logísticos (portos, hidrovias e rodovias) no oeste da Amazônia Paraense corrobora o acirramento e a materialização da grilagem de terras, dos conflitos agrários e territoriais, da manutenção da propriedade privada e da concentração fundiária.

AVALIAÇÃO DO COMPORTAMENTO DE BOVINOS E BUBALINOS DURANTE EXPOSIÇÃO FEIRA AGROINDUSTRIAL DO BAIXO AMAZONAS

Objetivou-se avaliar as principais alterações comportamentais dos animais confinados na feira agropecuária. O trabalho foi conduzido nas dependências do Parque de exposição Alacid Nunes, durante a XXXIX Feira Agroindustrial do Baixo Amazonas de 2016. Foram observados os comportamentos de ócio, alimentando, ruminando de 8 (oito) bovinos e 8 (oito) bubalinos, com pesos e idades semelhantes. No parque de exposições os animais foram alojados em duas baias de 4x4m², com bebedouros e comedouros, com cobertura de telhas de fibrocimento, com altura de 3m. Para a análise estatística, foi utilizado o teste de T de Student, a 5% de probabilidade, por meio do software MINITAB® 2014. O tempo despendido para ócio foi diferente entre bovinos e bubalinos no momento 21h (12,00±9,37 x 9,38±6,20). O tempo despendido na ruminação foi maior em bubalinos nos tempos 09h (4,09±5,30 x 10,00±10,65), 15h (6,13±8,97 x 10,58±8,56) e 21h (16,04±9,65 x 12,29±5,74), os bubalinos passaram mais tempo ruminando no horário mais frio do dia 06h (11,53±10,91 x 16,43±11,78). O pico de alimentação realizado pelos bovinos foi observado 9h (11,69±8,67 x 3,84±7,00) e para bubalinos o pico de alimentação às 21h (1,45±2,18 x 7,17±5,35). Do tempo total de ócio dos bubalinos, 77,02% ocorreu com animais em postura deitado e 17,27% em Pé. Por sua vez os bovinos apresentaram 69,75% desta atividade em Pé e 30,25% deitados. Conclui-se, que bovinos dispensam mais tempo nas atividades de alimentação, ócio e ruminação durante períodos mais quentes do dia, em contrapartida os bubalinos realizam suas atividades nos momentos mais frios do dia.PALAVRA-CHAVE: Búfalos, Comportamento, Estresse térmico, Nelore.

Amblyomma ticks infesting amphibians and Squamata reptiles from the lower Amazon region, Brazil.

Amphibians and Squamata reptiles belonging to a zoological collection were screened for ectoparasites, which were removed from the hosts and identified using morphological keys. Descriptive statistics and analysis of the association between the parasite and host characteristics (taxonomic group, capture location and habitat) were done. Among the 1256 animals examined (319 amphibians and 937 reptiles), 86 individuals were parasitized, corresponding to a frequency of 6.9% (6.6% reptiles and 7.5% amphibians). Ticks in the adult and nymph stages were identified to the species level; all of them belonged to the species Amblyomma dissimile. The larvae were identified to the genus level and were all Amblyomma sp. In total 69 larvae, 28 nymphs and eight adults were found. The most parasitized species was the frog Rhinella major: 24 parasitized animals of 65 examined (36.9%). There was a difference (P < 0.001) between parasitism by ticks of the genus Amblyomma with regard to the habitat of capture of the parasitized animal, with a higher parasitism rate in hosts that inhabited open areas as compared to animals ensconced in forest areas and edges of forests. New tick-host associations are given.

Constructing a logical model in school health: experience on the Lower Amazon region.

This experience report presents the construction of the theoretical and logic model for intervention to promote physical activity and healthy eating habits of the public schools students in the city of Parintins, Amazonas, Brazil. We carried out a theoretical research and also a documentary research on the School Health Program (PSE - Programa Saúde na Escola) on the national and local level, in addition to meetings with the PSE management committee for strategic planning of the actions. The municipality had no systematic structure of health practices at school. A theoretical and logical model that involved prerogatives of practice from the management of the municipality in PSE was developed. Actions to promote physical activity and healthy nutrition of primary and secondary school students were planned and promoted in schools of the PSE. Final considerations: Thus, the collective construction of this proposal contributed to the research of multi-sectoral practices related to the PSE principles and strategies, considering the particularities of the Lower Amazon context.

SPATIAL DISTRIBUTION OF ENVENOMATION BY SCORPIONS IN PARÁ STATE, BRAZIL

Scorpionism is recognized by the World Health Organization as a neglected disease and, in Pará State, Brazil, it is considered a public health hazard. The objective of this study was to describe the spatial distribution of envenomation caused by scorpions in Pará. The data related to envenomation were collected from 2007 to 2014 and used for both descriptive and transversal studies. For those studies records obtained from ongoing investigations from the database of the National Notifiable Diseases Information System at the Public Health Department of Pará Statewere used. Envenomation occurs year round, most often in the first half of the year, in males from the countryside, aged 20 to 59 years and taking up to 3 hours to reach medical care. The deaths occurred from ages 15 to 59. Regarding the severity of the cases, class I cases were the most frequent and class III cases were the least frequent, accounting for only 5.1% of all cases.Of the 144 municipalities of Pará State, in 126 the frequency of envenomation ranged from 1 to 1,208 cases per municipality. Thirteen municipalities located in the lower Amazon region and in the southwest of Pará State presented higher occurences, including the highest number of deaths.Scorpionism is present throughout Pará State. However, there were differences in severity and incidence in the various regions, with higher frequency in the southwest of the State and in the lower Amazon region, corresponding to the Tapajós and Guyana endemic areas in the BrazilianAmazon.

RAPID-COMMUNICATION Genetic diversity and differentiation in natural populations of Arapaima gigas from lower Amazon revealed by microsatellites.

Genetic variability is one of the important criteria for species conservation decisions. This study aimed to analyze the genetic diversity and the population differentiation of two natural populations of Arapaima gigas, a species with a long history of being commercially exploited. We collected 87 samples of A. gigas from Grande Curuai Lake and Paru Lake, located in the Lower Amazon region of Amazônia, Brazil, and genotyped these samples using a multiplex panel of microsatellite markers. Our results showed that the populations of A. gigas analyzed had high levels of genetic variability, which were similar to those described in previous studies. These two populations had a significant population differentiation supported by the estimates of FST and RST (0.06), by Bayesian analysis (K = 2), and by population assignment tests, which revealed a moderate genetic distance.

Seasonal and interannual dynamics of river-floodplain multispecies fisheries in relation to flood pulses in the Lower Amazon

River-floodplain fisheries are highly productive as seasonal water level changes, known as ‘flood pulses,’ increase the productivity of fish populations by providing them with feeding and reproductive opportunities in the floodplains. However, current understanding of flood pulse effects on fisheries activities at seasonal and interannual time scales remains deficient. Here, we analyze a comprehensive dataset of the Lower Amazon region to address the following questions: How flood pulses affect river-floodplain fishing strategies with respect to species composition and habitat? What is the interannual lag of hydrological effects on fisheries yields? And does that lag depend on the life-history strategy of the target fish species? A principal coordinates analysis indicated that fishing activities followed a clear seasonal pattern characterized by alternating habitat and species. Cross-correlation analyses indicated the existence of positive effects caused by mean water levels on fish catches roughly two or three years later. The lag of such water level effects on fish catches was proportional to species longevity, being 22 months for short-lived species with a mean age at catch of 21 months, 26 months for medium-lived species with a mean age at catch of 27.2 months, and 42 months for short-lived species with a mean age at catch of 33.7 months. The results of this study highlight the large seasonal and annual variability of tropical river-floodplain fisheries, and underscore the dependence of fish catches on natural river hydrological cycles. Because these fisheries are suffering increasing exploitation pressures, conservation measures are necessary to protect the hydrology of Amazonian rivers.