Reserva De Desenvolvimento Research Articles

Impact evaluation of the extreme weather event in mangroves of the Brazilian Southeast Coast with remote sensing

Among the various environments present on the planet that deserve due attention, as they have particularities and specificities of chemical, physical and biological orders, mangroves stand out. These ecosystems are mostly located in the intertropical zones where continental and oceanic waters meet, being crucial for a great diversity of animal species that find, in it, conditions that allow them to live and reproduce. In addition, this ecosystem is also for many local residents, such as traditional fishermen and crab farmers, a place for income generation, thus assuming an important socio-economic function. In addition, mangroves, through vegetation, help to protect the coast and act as important carbon sequestrants and stores. Among the less invasive methodologies that make it possible to analyze a series of dynamics of this environment, reducing costs with the field and the risks inherent to its natural characteristics, Remote Sensing stands out. Therefore, the general objective of this research was to evaluate the effectiveness of the NDVI, SAVI and LAI vegetation indices in recording the consequences of an extreme climatic event that occurred on June 1, 2016, in the mangroves of the Reserva de Desenvolvimento Sustentável Municipal Piraquê Açu-Mirim, located in Aracruz (ES), Southeast Coast Brazil. To achieve the objective, time series between February 2016 (before the event) and December 2020 were used. The results, which include maps and statistical graphs, allowed the delimitation of areas according to the intensities of the impacts and their consequences on the vegetation. While the vegetation of Piraquê-Açu underwent regeneration processes in all affected areas, in Piraquê-Mirim the area with the greatest impact remained destroyed. Given the socio-environmental importance of mangroves, it is necessary to implement projects aimed at their recovery. Both the methodology and the indices were efficient to achieve the objectives and can be reproduced in other mangroves.

New species of Parapharyngodon (Nematoda: Pharyngodonidae) parasite of Osteocephalus taurinus (Anura: Hylidae) from Northern Brazilian Amazon Region.

Parapharyngodon spp. are nematodes parasites of amphibian and reptiles worldwide distributed. Of 55 valid species, only 11 are known for the Neotropical realm, and six were found parasitizing hylid frogs in the world. In the present work, we describe a new species of Parapharyngodon from the large intestine of Osteocephalus taurinus from Reserva de Desenvolvimento Mamirauá, Amazonas, Brazil, using light and scanning electron microscopy. Parapharyngodon curupira n. sp. is allocated to the group of species with three pairs of cloacal papillae. However, it shows a set of different morphological characters compared to its congeners. In the new species, males have gubernaculum and smooth cloacal lip, females have pre-bulbar ovaries, and we also observed some morphometric differences. Among Parapharyngodon spp. from the Neotropical realm, the new taxon resembles P. alverangai and P. politoedi. The last species was described from the same host and biome (Amazon); however, they can be easily distinguished from new species by the presence of gubernaculum and v-shape structure at the lower caudal lip. Thus, we characterize and propose a new species of Parapharyngodon from the western amazon.

Migração rural-urbana por demanda educacional no Médio Solimões, Amazonas

ABSTRACT This paper aims to analyze the relationship between rural-urban migration and education in the context of a traditional riverside population of the Amanã Sustainable Development Reserve (Reserva de Desenvolvimento Sustentável Amanã), in the State of Amazonas, Brazil. This paper is also aimed at identifying how the context of migration in the conservation unit differs from other studies related to educational inequalities. Quantitative data Demographic and Economic Monitoring System the Mamirauá Sustainable Development Institute (Sistema de Monitoramento Demográfico e Econômico do Instituto de Desenvolvimento Sustentável Mamirauá) were used to compare the changes in the migratory and educational context of 69 rural locations in the Amanã Sustainable Development Reserve, 568 households in 2011 and 676 in 2018. The results showed an increase of 71% in rural-urban migration due to educational factors, and a change in the educational profile of residents, highlighting a new demand for education in the area. The unmet educational need has influenced the migratory decisions of the residents, a consequence of the distance between educational policies and the reality of the rural Amazon region.

The role of fishery management and environmental variables on the fish fauna in floodplain lakes in the lower Purus River, Amazon Basin, Brazil

AbstractPeriodically flooded environments in the Amazon River basin are recognized as being highly productive because of their limnological dynamics and ecological heterogeneity. They also have been historically impacted by fishery activities, therefore being crucial ecosystems to be considered in small‐scale conservation policies. Previous studies, however, did not detect or assess significant or consistent positive effects of combinations between protected areas or environmental variables on ichthyofauna. Accordingly, the present study analysed the effects of fishery management (hereafter categorization of lakes) and environmental characteristics on the attributes of fish assemblages in 20 floodplain lakes (eight categorized as open access; 12 categorized as protected lakes) inserted in a legally protected area, the Reserva de Desenvolvimento Sustentável Piagaçu‐Purus (RDS‐PP) in the lower Purus River, Amazonas State, Brazil. The results of the present study indicated depth, surface area and lake categorization synergistically influenced the ichthyofauna of these floodplain lakes. It also suggests this influence should not be treated separately in management policies. It was concluded that the potential effectiveness of fishery management in floodplain lakes is closely related to small‐scale (i.e. local) interventions, with emphasis on the role of the lakes as a unit of effective management of ichthyofauna in floodplains. Furthermore, participatory decisions during the process of elaborating management plans for floodplain lakes should consider environmental attributes relevant to biological communities and traditional knowledge.

Predicting the potential distribution of aquatic herbaceous plants in oligotrophic Central Amazonian wetland ecosystems

Aquatic herbaceous plants are especially suitable for mapping environmental variability in wetlands, as they respond quickly to environmental gradients and are good indicators of habitat preference. We describe the composition of herbaceous species in two oligotrophic wetland ecosystems, floodplains along black-water rivers (igapó) and wetlands upon hydromorphic sand soils (campinarana) in the Parque Nacional do Jaú and the Reserva de Desenvolvimento Sustentável Uatumã in Central Amazonia, both protected areas. We tested for the potential distribution range (PDR) of the most frequent species of these ecosystems, which are the ones that occurred in at least two of the sampled wetlands, using species distribution models (SDMs). In total, 98 aquatic herbaceous species were recorded, of which 63 occurred in igapós and 44 in campinaranas. Most igapó species had ample PDRs across the Neotropics, while most campinarana species were restricted to the Amazon Basin. These results are congruent with studies that described similar distribution patterns for tree and bird species, which emphasizes a high degree of endemism in Amazonian campinaranas. However, we also found differences in the potential distribution of species between the two protected areas, indicating high environmental variability of oligotrophic ecosystems that deserve further investigation to develop effective measures for their conservation and protection.

Ichthyofauna from floodplain lakes of Reserva de Desenvolvimento Sustentável Piagaçu-Purus (RDS-PP), lower rio Purus

Abstract: The ichthyofauna of the rio Purus has been little investigated, especially in its lower portion, characterized by diverse aquatic environments, especially in flooded areas. We inventoried the ichthyofauna of floodplain lakes with different management efforts in Reserva de Desenvolvimento Sustentável Piagaçu-Purus (RDS-PP), which represent important resource for commercial fishing in North region, in the first illustrated inventory of the fish fauna from lower rio Purus. We surveyed 20 lakes, classified as open access (eight lakes) and protected (12 lakes) during 2009 low water levels. A total of 2,299 individuals were collected, represented by seven orders, 25 families and 74 species. Characiformes was the most representative order in number of species and families, followed by Siluriformes, Cichliformes, Gymnotiformes, Clupeiformes, and Osteoglossiformes. Most abundant and frequent species were Pygocentrus nattereri, Triportheus angulatus, Serrasalmus sp. "2n=58", Pterygoplichthys gibbiceps, and Osteoglossum bicirrhosum. Protected lakes presented higher species richness compared to open access lakes. Similarly, protected lakes possessed 26 species occurring exclusively, with emphasis on Colossoma macropomum, an important species for fisheries due to its commercial importance. We added 44 new records of fish species for the lower rio Purus. Our results indicate the potential efficiency of zoning systems of open access and protected lakes established by local population and ruled by RDS-PP for fisheries management. Therefore, we strongly suggest its maintenance for conservation of ichthyofauna of floodplain lakes of lower rio Purus.

Infracommunities of bat flies (Diptera: Streblidae and Nycteribiidae) of bats (Mammalia: Chiroptera) in three conservation units in the State of Amapá, Brazil

Abstract: Diptera belonging to the families Nycteribiidae and Streblidae are hematophagous ectoparasites, exclusively of bats. The Amapá State is located in the North Region of Brazil. The Amapá represents one of with the lowest rates of deforestation in the country, with approximately 80% of the territory preserved. Within the State, there are conservation units, Floresta Nacional do Amapá (FNA), Parque Nacional Montanhas do Tumucumaque (PNMT) and Reserva de desenvolvimento Sustentável do Rio Iratapurú (RDSI). These areas represent priority areas for the Conservation of Amazonian Biodiversity. Recently in Amapá studied on the diversity and distribution of bats, however, there are no records of associated arthropod ectoparasites. Therefore, the objective was to describe the pattern of association of Nycteribiidae and Streblidae species on bats in three protected areas of Amapá. Bats were collected through mist nets, where each host had its body visually revised and the Diptera collected were identified through a specific bibliography. One thousand and eighty- six individuals of bats flies were identified, distributed in 52 species (Streblidae = 49 and Nycteribiidae = three). Among the three infracommunities, the PNMT infracommunities was the largest found with abundance and richness of bats flies. All species found, represent new occurrences for the Amapá, being these, 18 new records for the North Region and seven new records for Brazil.

The Giant Tree Rat, Toromys grandis (Wagner, 1845): new record with range extension and comments on its morphology, biology and conservation

Abstract We present data on a new record of Toromys grandis, a species not sampled for almost 60 years. The species is known from the newly-collected specimen and 206 specimens housed in museums worldwide. The gut morphology, consisting of very long intestines and well-developed caecum, suggest that T. grandis is a potential herbivore also adapted to omnivory. Our record at the Reserva de Desenvolvimento Sustentável (RDS) Piagaçu-Purus extends the range of T. grandis approximately 150 km southwestward and represents the second record of the species within a protected area.

Hepatic and Renal Lesions in Free Ranging Black Caimans (Melanosuchus niger) in the Brazilian Amazon for Human Consumption

Background: The black caiman (Melanosuchus niger), belongs to the order Crocodylia, family Alligatoridae. More than a hundred species of helminths, mainly trematodes and nematodes, parasitize crocodilians around the world and a considerable number of species of ascaris have been described in crocodilians. There are few descriptions of hepatic and renal diseases affecting M. niger, and no articles related to the histopathological aspects of this species were found. The aim of this study was to evaluate gross and microscopically the liver and kidneys of 100 specimens of Melanosuchus niger slaughtered in Reserva de Desenvolvimento Sustentável Mamirauá, from natural populations.Materials, Methods & Results: The capture of the alligators was performed during the night, by members of the community itself in the channels and lagoons of the Reserve's lowland ecosystem. For the capture procedures, ties and harpoons were used and the animals were identified through the red glow of the eyes using the spot light lanterns. After being conducted to the slaughter area, the animals were submitted to the previous biometry to select which animals were appropriated for slaughter, they should measure between 2.10 m and 2.80 m. A total of 88 livers and 95 kidneys of M. niger of natural populations were analysed gross and microscopically, independently of gross lesions. The fragments collected for histopathological examination were approximately 0.5 cm thick and they were packed in appropriated identified containers with formalin 10% solution. The collection procedures were accompanied by field records for data recording. After fixation of the collected material, it were processes by habitual techniques for paraffin inclusion and hematoxylin-eosin staining. Grossly, none of the livers examined presented alterations and two kidneys presented parasitism. The hepatic microscopic analysis indicates in 3/88 cases, multiple foci of necrosis. In 7/88 cases, it was observed in the hepatic parenchyma, granulomas, mainly with epithelioid cells. In the histopathological examination of the kidney, the only alteration observe in 8/95 cases was the presence of granulomas.Discussion: The occurrence of Sebekia oxycephala nymphs, a pentastomid, in the liver of Alligator mississippiensis was reported in other researches. The parasite Sebekia mississippiensis was observed in liver and lungs of A. mississippiensis. similar alterations were also noticed in this research. The coccidiosis related to hepatic manifestations in crocodilians is related to the parasite that may belong to the genus Goussia. In the liver, under the oocysts form leads to a diffuse hydropic degeneration of hepatocytes. In this study it was also observed the hydronic degeneration, however, associated to the necrosis areas that had in the periphery epithelioid cells infiltrated, without parasitic participation. Two renal trematodes are known in crocodilians, Deurithrema gingae and Renivermis crocodyli both in Crocodylus porosus. Also it was found in the renal parenchyma few encapsulated and well delimited parasites by a severe tissue reaction. Based on the gross and microscopic found, it is concluded that liver and kidney, although multiple organ functions, were not prone to infections, with granulomas being the main manifestation, and the etiopathogenesis of the areas of hepatic necrosis could not be defined.

Melastomataceae in the Reserva de Desenvolvimento Sustentável do Tupé, Amazonas, Brazil

We present a taxonomic study of the Melastomataceae that occur in the “Reserva de Desenvolvimento Sustentável do Tupé”, lower Negro River, Amazonas. Forty-two species from nine genera: Miconia (21 spp.), Clidemia (6 spp.), Aciotis, Bellucia and Tococa (3 spp. each), Henriettea and Tibouchina (2 spp. each), Adelobotrys and Maieta (1 sp. each). We present detailed descriptions and an identification key prepared through DELTA software. We also present illustrations and data on geographical distribution for the species. This study presents the first record for 27 species in the Reserve.

A pesca e o conhecimento ecológico local dos pescadores de acará-disco (Symphysodon aequifasciatus, Pellegrin 1904: Cichlidae) na Reserva de Desenvolvimento Sustentável Piagaçu-Purus, baixo rio Purus, Brasil

O acará-disco (Symphysodon aequifasciatus, Pellegrin 1904), peixe endêmico da bacia amazônica, é uma das espécies ornamentais mais conhecidas do mundo. Apesar disso, informações sobre a explotação desse animal em vida livre são quase inexistentes na literatura científica. Nesse artigo, a pesca de pequena escala do acará-disco na Reserva de Desenvolvimento Sustentável Piagaçu-Purus (RDS-PP), baixo rio Purus, Amazonas, é caracterizada com base em entrevistas estruturadas e abertas com pescadores e habitantes, bem como em observações de campo. A pesca do acará-disco é sazonal, ocorrendo durante o período de seca. É realizada por pescadores locais, utilizando atratores de pesca e uma técnica de detecção e estimativa de abundância por mergulho em apneia. O armazenamento local é feito em tanques de madeira e os peixes são transportados em recipientes plásticos para distribuição nos mercados regionais por meio de barcos dos próprios pescadores, barcos de linha ou jangadas. Os peixes são vendidos para empresas exportadoras especializadas de Manaus. Neste estudo, descrevemos o conhecimento ecológico local dos pescadores de acará-disco na RDS-PP e discutimos sua importância para a gestão da pesca nessa unidade de conservação.

Karyotypic similarities between two species of Rhamphichthys (Rhamphichthyidae, Gymnotiformes) from the Amazon basin

The family Rhamphichthyidae includes three genera: Rhamphichthys Müller et Troschel, 1846, Gymnorhamphichthys M. M. Ellis, 1912 and Iracema Triques, 1996. From this family, only the species Rhamphichthys hanni Meinken, 1937 has had its karyotype described. Here, we describe the karyotypes of two additional Rhamphichthys species: Rhamphichthys marmoratus Castelnau, 1855 from the Reserva de Desenvolvimento Sustentável Mamirauá, Amazonas state and Rhamphichthys prope rostratus Linnaeus, 1766 from Pará state, both in Brazil. Our karyotypic analyses demonstrated that the diploid number is conserved for the genus (2n = 50), but the karyotypic formulas (KFs) differed between Rhamphichthys marmoratus (44m/sm+6a) and Rhamphichthys prope rostratus (42m/sm+8a). In both species, the constitutive heterochromatin (CH) was located in the centromeric region of most chromosomes. Large heterochromatic blocks were found on the long arms of pairs 4 and 14 in Rhamphichthys marmoratus and on chromosomes 3, 4 and 19 in Rhamphichthys prope rostratus, which also has a heteromorphism in chromosome pair 1. The CH was DAPI positive, indicating that it is rich in AT base pairs. The Nucleolus Organizer Region (NOR) showed staining at a single location in both species: the long arm of pair 1 in Rhamphichthys marmoratus and the long arm of pair 12 in Rhamphichthys prope rostratus, where it showed a size heteromorphism. CMA3 staining coincided with that of Ag-NOR, indicating that the ribosomal genes contain interspaced GC-rich sequences. FISH with an 18S rDNA probe confirmed that there is only one NOR site in each species. These results can be used as potential cytogenetic markers for fish populations, and comparative analysis of the karyotypes of Hypopygus Hoedman, 1962, Rhamphichthys and Steatogenys Boulenger, 1898 suggests that the first two genera diverged later that the third.

Relações dendrométricas em fragmentos de povoamentos de pinus, em Minas Gerais

The aim of this work was to adjust diameter distribution, hypsometric relation, taper and volume models to characterize the dendrometric relations on remaining fragments of Pinus sp. from stands of the 1970s, in the region where the Reserva de Desenvolvimento Sustentavel Veredas do Acari is located, north of the state of Minas Gerais. The identification of the Pinus sp. fragments and its mapping was made. Biometric data were gathered from trees for modeling the diameter distribution, hypsometric relationship, taper and tree volume. The selection criteria for the models consisted on evaluation of the adjusted determination coefficient, standard error of estimate in percentage, F-test, regression coefficients significance and residuals graphical analysis. The Beta function, Naslund, Max-Burkhart and Schumacher-Hall models were adequate to describe, respectively, diameter distribution, hypsometric relationship, taper and tree volume for Pinus sp., on fragments of the 1970s, in the state of Minas Gerais.

Reserva de desenvolvimento sustentável: avanço na concepção de áreas protegidas?

O movimento ambiental, denominado socioambientalismo, foi pioneiro ao reconhecer a intrínseca ligação entre as questões sociais e ambientais e apresenta uma importante atuação na sociedade civil brasileira em defesa dos direitos dos povos tradicionais. A Reserva de Desenvolvimento Sustentável (RDS) é uma categoria essencialmente socioambiental, pois incorpora aos objetivos da conservação, ações de inclusão social, valorização do conhecimento local e práticas de manejo ambiental. O trabalho objetivou investigar a percepção ambiental e o nível de envolvimento da população com relação à RDS Ponta do Tubarão, localizada no estado do Rio Grande do Norte. Foram realizadas entrevistas abertas e semiestruturadas (n=262) e a análise de conteúdo evidenciou que a maioria dos entrevistados atribuiu importância à área protegida; todavia, constatou-se um alto nível de insatisfação com sua gestão e desconhecimento dos seus objetivos, detectaram-se inúmeros conflitos socioambientais, com destaque para proibição de construções e foram propostas alternativas para melhoria da qualidade de vida local. Esse trabalho conduz a uma reflexão da prática de gestão da área protegida estudada e espera-se que os dados obtidos possam subsidiar o plano de manejo local e minimizar os conflitos socioambientais existentes na área.

Short Communication Population genetics analysis of Podocnemis sextuberculata (Testudines, Podocnemidae): lack of population structure in the central Amazon Basin

The chelonians are, in general, important for the economy of the traditional populations of the Amazon region, especially as a source of animal protein. Furthermore, sub-products, such as eggs and fat, are utilized in the manufacture of cosmetics, and the plastron and carapace are used in the manufacture of adornments. The freshwater turtle species Podocnemis sextuberculata, locally known as "iaçá" or "pitiú", is widely distributed in the Amazon Basin in Brazil and also in Colombia and Peru. This species is on the International Union for Conservation of Nature Red List in the category of vulnerable species. We examined the genetic variability and population structure of three populations represented by 64 individuals sampled from Reserva Federal de Abufari, Tapauá, Amazonas State; Reserva de Desenvolvimento Sustentável Mamirauá, Tefé, Amazonas State, and Terra Santa, Pará State. All of these are over 1000 km from each other. A partial 415-bp sequence of the mitochondrial gene ND1 was utilized as a molecular marker. Seven haplotypes were observed; the most common haplotype was shared by all the areas sampled, while the rarest haplotypes were represented by a single individual and were thus restricted to a single locality. The sharing of the most common haplotype, the high number of migrants (Nm) and the AMOVA results indicate a lack of genetic structure among the sampling localities. The levels of genetic variability observed were homogeneous among the sampling localities. These results (Ө(ST) and Nm) are compatible with what is known about the ecology of this species, which has a great migratory capacity.

Fish assemblages in two sandy beaches in lower Purus river, Amazonas, Brazil

Fish assemblages from two sandy beaches in the lower Purus river (Amazonas, Brazil) were compared. Four sampling groups were represented by: day and night samples in sandy beach inside the Reserva Biológica de Abufari (biological reserve) and day and night samples in the Reserva de Desenvolvimento Sustentável Piagaçu-Purus (sustainable development reserve). Samples were collected during low water levels (November) in 2007. The fish were sampled by means of seines with mesh size of 5 mm between opposing knots, 11 m long and 6 m wide. A total of 112 fish species belonging to nine orders and 27 families was captured. The vast majority of the dominant forms consisted of small fishes (< 100 mm SL) or juveniles. Samples collected in Abufari at night presented more specimens (3,540), higher richness (84 spp.), larger total biomass (76,614 g) and higher diversity (H'= 2.57) than the other groups. The composition of fish assemblages was significantly different among all analyzed groups (ANOSIM, p < 0.0001, R= 0.71). NMDS analysis also clustered all species in four distinct groups according to species composition per period and site. SIMPER analyses showed that 80% of variation of species composition among the groups examined was due to 12 species. However, fish composition did not show any correlation with the abiotic factors examined. Different levels of use in both reserves may explain differences in fish composition.

New terebellids (Polychaeta: Terebellidae) from northeastern Brazil

Four new species of terebellid polychaetes were collected at the Reserva de Desenvolvimento Sustentável da Ponta de Tubarão, State of Rio Grande do Norte, northeastern Brazil. These species are Streblosoma patriciae sp. nov., Terebella leslieae sp. nov., Nicolea ceciliae sp. nov., and Pista alonsae sp. nov. All these species are herein described and compared with the morphologically most similar congeners.

Morfodinâmica de um Canal de Maré Tropical: Estudo de Caso na Costa Norte Rio Grandense, Nordeste do Brasil

This paper examines the tidal inlet morphodynamics on a tropical sandy coast, located on the “Reserva de Desenvolvimento Sustentavel Ponta do Tubarao-RDSPT...

Tree species distribution inVárzea forests of Brazilian Amazonia

Amazonian varzea forests are floodplains inundated by nutrient-rich white-water rivers occurring along the Amazon River. They are regularly flooded for up to 210 days per year by water columns of 10–15 m. Topographic variation results in different flooding amplitudes and durations along the flooding gradient, where the different tolerance to flooding of different plant species results in a vegetation zonation. We made a review of literature about the vegetation composition ofvarzea floodplain forests of Brazilian Amazonia along the Amazon River. Twenty-two studies were selected. Basing on the distribution of inventories which are concentrated in three main areas around the three larger cities Belem, Manaus and Tefe, we classified the inventories into three regions: (A) Estuary region with flooding regime influenced by daily inundations linked to the tides; (B) Central Amazonia near Manaus; (C) Western part of Brazilian Amazonia bordering Peru and Colombia, including Tefe and the “Reserva de Desenvolvimento Sustentavel Mamiraua”. Summarizing the analyzed species lists, 36 tree species were registered in all sampled regions including the estuary. The regions A +C have 63 species in common, region B+C 143, and A+B 50. In the inventories analyzed here, an increase in species numbers from East to West can be confirmed, but it is difficult to state whether this is not an artefact due to local sampling. Vertical zonation patterns are difficult to discuss due to the lack of comparable data. The inventoried areas are small, and there is an urgent need for comparable floristic inventories throughout the basin. Destruction is spreading rapidly and the traditional use of forests and its resources is changing to a destructive exploitation that already has changed much of the physiognomy and diversity of this unique ecosystem.

Estrutura populacional, razão sexual e abundância de Podocnemis sextuberculata (Testudines, Podocnemididae) na Reserva de Desenvolvimento Sustentável Mamirauá, Amazonas, Brasil

Population structure, sex ratio and abundance of Podocnemis sextuberculata (Testudines, Podocnemididae) in the Reserva de Desenvolvimento Sustentavel Mamiraua, Amazonas, Brazil. We studied turtles in the focal area of the Reserva de Desenvolvimento Sustentavel Mamiraua from September 1996 through August 1998. The reserve is located in the western part of the Brazilian Amazon, between the Japura, Solimoes, and Auti-Parana rivers, near the city of Tefe, in the state of Amazonas. In this study the populacion structure, sex ratio and abundance of Podocnemis sextuberculata were investigated. We intensively studied the population of turtles in the Jaraua river basin in order to determine population structure. We sampled turtles in different sectors of the focal area of the reserve for one month each year during July and August 1997 and 1998. We captured the turtles using flag gill nets and trammel nets. The type of net and size of the nets used influenced the size of the turtles captured. The nets used by the local fishermen were sexually selective in the capture of turtles. Seventy two per cent of the P. sextuberculata captured were adults; 13 % juveniles and 14.7 % subadults. During the second year of the study we found a lower density of turtles in the five areas which we sampled both years. The sex ratio of captured P. sextuberculata was 1.87 males per female.