Summary Weight‐length relationships (WLR) are presented for 40 fish species inhabiting the mangrove creeks in the Curuçá Estuary in Northern Brazil. Samples were taken bimonthly between July 2003 and 2004 with a fyke net. This study represents the first reference available on WLR for 28 fish species.

The assumption for this study was that litterfall in floodplain environments of the middle Xingu river follows a pattern of seasonal variation. According to this view, litterfall production (total and fractions) was estimated in four alluvial rainforest sites on the middle Xingu River over an annual cycle, and examined the effect of seasonal flooding cycle. The sites included two marginal flooded forests of insular lakes (Ilha Grande and Pimentel) and two flooded forests on the banks of the Xingu itself (Boa Esperança and Arroz Cru). Total litterfall correlated with rainfall and river levels, but whereas the leaf and fruit fractions followed this general pattern, the flower fraction presented an inverse pattern, peaking in the dry season. The litterfall patterns recorded in the present study were consistent with those recorded at other Amazonian sites, and in some other tropical ecosystems.Keywords: alluvial rainforest, fractions of litter production, middle Xingu River.Efeito da variação da inundação sazonal na produção de serrapilheira numa floresta aluvial do médio Rio Xingu (bacia do Amazonas, Brasil) ResumoO pressuposto para este estudo foi que a produção de serrapilheira nos ambientes inundáveis do médio rio Xingu, segue um padrão de variação sazonal. Assim, se quantificou durante um ciclo anual a produção de serapilheira total e de suas frações, e se indagou a correlação entre o regime do nível do rio e a produção de serapilheira. Quatro ambientes de floresta ombrófila aluvial foram estudados: duas florestas inundáveis de lagoas insulares (Ilha Grande e Pimentel) e dois ambientes de floresta marginal no canal principal do rio Xingu (Boa Esperança e Arroz Cru). A produção de serapilheira total nos quatro ambientes mostrou um padrão sincrônico com a variação do nível do rio e com a inundação das áreas marginais. Por sua vez, foi evidente um aumento da produção de frutos durante a inundação local e de forma inversa uma maior produção de flores com o regime de seca. Os padrões registrados para os componentes de serapilheira do médio rio Xingu, confirmam os achados para outros ambientes amazônicos e tropicais.Palavras-chave: floresta ombrófila aluvial, produção de serrapilheira, médio Rio Xingu.

Assessing artisanal fishing effort and catches in remote tropical coastal areas is a continuous challenge for fisheries data collection. This is the first spatio-temporal analysis of the large tidal weir (LTW) fishery operating on intertidal sand banks along the world’s longest mangrove coast, north Brazil. Airborne synthetic-aperture radar (SAR) images and aerial photos were integrated with field sampling to investigate catch and discard compositions of seven LTW during the main fishing season. LTW measurements on the SAR images were used to generate estimates on daily catch, wood extraction, and sand accumulation. In a coastal stretch of 67 km, 793 LTW were identified on SAR images from 2004, including 573 active LTW. The number of active LTW in Taperaçú Bay and Caeté Bay had increased from 87 in 1998 to 132 in 2004 (52% increase), and from 92 to 202 (106% increase), respectively. Sixty-five fish species from 24 families were captured in the LTW. Ariidae, Sciaenidae, Haemulidae, and Carangidae accounted for 45, 20, 10, and 7% of the total sampled catch weight of 3441 kg, respectively. The mean daily catch per LTW was 110 kg ± 9 SE. Total discards in outer estuarine LTW were >3 times higher than in inner estuarine LTW. All Aspredinidae, Belonidae, Tetraodontidae, and Trichiuridae, and >75% of Auchenipteridae, Clupeidae, Engraulidae, Ephippidae, Loricariidae, Scombridae, and Soleidae were discarded. The LTW fishery apparently practices balanced harvesting; however, the massive LTW increase suggests fishing effort reduction to moderate levels. Mangrove wood extraction for LTW construction (22 835 m3 or 855 390 trees) and sand accumulation (144 802 m3) likely have only local scale effects, negligible for the overall ecosystem dynamics. The study highlights the potential of SAR images for use in fisheries data collection and management of tropical coasts, emphasizing the need for integration with ground-truthing field studies.

Length-weight relationships (LWR) of 14 fish species were estimated from Palito Mountain ridge, upper Tapajós river basin, Brazilian Amazon region. This study represents the first LWR to the small characid Hemigrammus marginatus, and additionally provides new maximum record of length and weight for three species.

This study reports on the length-weight relationships and condition factor for the endangered rheophilic fish Ossubtus xinguense Jégu from Rio Xingu rapids. This species is threatened by construction of the third largest hydroelectric in the world, the Belo Monte dam close to the city of Altamira, northern Brazil. Specimens were collected in the dry season between July 2012 and September 2012. Male specimens have body length larger than females, atypical in serrasalmid fishes, and different length-weight relationships were found between adult and juvenile specimens. This study presents the first biological characteristics for O. xinguense.Keywords: conservation, hydroelectric impacts, growth stanzas, rheophilic fish, endemic species.Relações peso-comprimento e fator de condição do pacu-capivara Ossubtus xinguense Jégu, 1992 (Characiformes, Serrasalmidae), uma espécie ameaçada de extinção das corredeiras do Rio Xingu, norte do Brasil ResumoEste estudo relata as relações peso-comprimento e fator de condição para o peixe reofílico ameaçado de extinção Ossubtus xinguense Jégu. Esta espécie, endêmica das corredeiras do Rio Xingu, é ameaçada pela construção da terceira maior hidrelétrica do mundo, denominada Belo Monte localizada às proximidades da cidade de Altamira, norte do Brasil. Os espécimes foram coletados na estação seca do rio, entre julho e setembro de 2012. Espécimes machos apresentaram tamanho corporal maior que fêmeas, condição atípica entre os peixes serrasalmídeos, e diferentes relações peso-comprimento foram encontradas entre espécimes juvenis e adultos. Este estudo apresenta as primeiras características biológicas para O. xinguense.Palavras-chave: conservação, impactos por hidrelétricas, estrofes de crescimento, peixe reofílico, espécie endêmica.

This study records some mollusk species from the Gastropod associated with rapids in the main channel of the middle Xingu River. The samples were gathered along marginal shores of the River, in sand-rock substrates. Based on the total length and width of the shell, their frequency distribution were built and the regression of these two parameters was made. Of the 185 specimens collected, 44 was of Pomacea canaliculata (Lamarck, 1804), (13,0-82,0mm); 65 of Doryssa heathi (Baker, 1914), (20,0-47,0mm); 30 Doryssa starksi (Baker, 1913), (15,2-66,0mm) and 46 of Doryssa sp. nov. sensu Simone, 2007 (6,0-23,7mm). The linear regression equations were calculated for the 3 species of Doryssa. The invasion of the alien gastropod species Melanoides tuberculatus in the nearby tributaries of the Xingu River, and its high competitive advantage in relation to the local species, could be lead to the extinction of these Amazon mollusk species.

Summary Length–weight relationships (LWR) were provided for three fish species from Cujubim Sustainable Development Reserve, drainages of the Jutaí River Basin, a tributary of the Solimões River, part of the Central Amazon Biodiversity Corridor, Amazonas, Region North of Brazil. Specimens were collected in March 2006 using gill nets with mesh sizes range between 2 and 18 cm. The LWRs for all species are provided by the first time, and two new maximum length are recorded.

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