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Oyster culture has benefited traditional coastal communities along the Amazon macrotidal mangrove coast of Pará state in Brazil since 2006. Currently, seven oyster culture units in five municipalities are expanding production, but with no environmental monitoring, which is important for the control of the impacts of oyster culture on waters as well as for oyster management and conservation. Seasonal variation in environmental characteristics of the water was evaluated at all oyster culture units in Pará, from September to November 2013 (dry season) and February to April 2014 (wet season), to generate baseline data to evaluate future impacts and aid strategic planning, such as diversifying seed production. Salinity, dissolved oxygen, pH, oxidation-reduction potential, depth, temperature, and chlorophyll-a concentration were measured during flooding and ebbing tides, and compared between seasons and among culture units using uni- and multivariate statistics. All variables were significantly higher in the dry season, except depth, which was significantly greater in the wet season. Mean salinity, which varied from 2.4 to 46, explained most of the variation among culture units in relation to season, sampling date within each season and tidal state. However, dissolved oxygen, pH and depth were also important. Oyster culture units in Pará may be suitable for sustainable harvesting of seed/spat from the wild (lower salinity and pH), or for on-growing (higher salinity, higher pH, and greater depth). Seasonal variation is sufficient to allow both activities at most units at appropriate times of the year, which would help increase oyster production in Pará. RESUMO A ostreicultura beneficia comunidades costeiras tradicionais ao longo da costa do manguezal de macro-marés amazônico do Estado do Pará no Brasil desde 2006. Atualmente, sete cultivos em cinco municípios expandem sua produção, mas sem monitoramento ambiental, importante para verificar impactos da ostreicultura sobre as águas, mas também para o manejo e conservação de ostras. A variação sazonal nas características ambientais da água foi avaliada em todos os cultivos do Pará, de setembro a novembro de 2013 (estação seca) e fevereiro a abril de 2014 (estação chuvosa), para gerar dados de base para avaliar futuros impactos e ajudar no planejamento estratégico, como a diversificação da produção de sementes. Salinidade, oxigênio dissolvido, pH, potencial de oxidação-redução, profundidade, temperatura e concentração de clorofila-a foram medidas durante as marés inundantes e vazantes, e comparadas entre estações e unidades de cultivo usando estatísticas uni- e multivariadas. Todas as variáveis foram significativamente mais elevadas na estação seca, exceto profundidade, que foi significativamente maior na estação chuvosa. Salinidade média, que variou de 2,4 a 46, explicou a maior parte da variação entre as unidades de cultivo em relação à estação, data de amostragem dentro de cada estação e estado das marés. No entanto, oxigênio dissolvido, pH e profundidade também foram importantes. As unidades de cultivo de ostras no Pará são apropriadas para colheita sustentável de sementes na natureza (menor salinidade e pH) ou para engorda (maior salinidade, maior pH e maior profundidade). A variação sazonal permite ambas atividades na maioria das unidades, no período apropriado do ano, e ajudaria a aumentar a produção de ostras no Pará.

In an effort to develop molecular tools for oyster identification, this study reveals the usefulness of a multiplex polymerase chain reaction (PCR) for the reliable, rapid and low-cost identification of the four oyster species found along the Brazilian coast: Crassostrea gasar, Crassostrea rhizophorae, Crassostrea gigas and Crassostrea sp. Canela originally found at Para, Brazil. In order to perform a simultaneous identification of these species, we used a set of five primers developed and adapted from the cytochrome oxidase subunit I (COI) and internal transcribed spacer 1 (ITS1) fragments, respectively. Amplification was successful in all four species and PCR products were visualized in agarose gel. A single reaction was capable of distinguishing between the species: C. gigas, with two fragments (236 bp for COI and 718 bp for ITS1); C. gasar, with one fragment (718 bp for ITS1); Crassostrea sp., with one fragment (621 bp for ITS1) and C. rhizophorae with two fragments (377 bp for COI and 718 bp for ITS1). This molecular approach provides a simple and rapid identification of the oyster species from the Brazilian coast, thus increasing the efficient and quality of oyster culture programs by reducing the risk of wrong species identification.

Management and culture of mangrove oysters may reduce harvesting pressure on natural populations in northern Brazil. Densities of oyster seed, scars and other epibenthos on plastic sheets and bottles were observed over two years at a mangrove island (Ilha Canela), Bragança, Pará, northern Brazil. The only oyster species found settling on the substrates was a possibly exotic oyster (Crassostrea sp. canela) that is closely related to Indo-Pacific Crassostrea and that also occurs in southern China. Densities of seed and scars of Crassostrea sp. canela on bottles were about half those on sheets. Seed and scars predominated (>95% relative abundance) on both collectors. Although densities of other epibenthos were low and irregular, these were positively correlated with densities of seed on both collectors. Oyster seed and barnacles on sheets were more abundant in the wet season. However, in the dry season, seed predominated on the inside of bottles, a refuge from predation or desiccation or both, whereas oyster scars and barnacles were more abundant on the outside. The target species for oyster culture in Pará is Crassostrea gasar. Oyster growers are concerned about potential impacts of Crassostrea sp. canela, the larvae of which appear to prefer high salinity. Seed is regular and abundant as densities exceed published figures for several other Crassostrea species. Knowledge of the timing and density of settlement of this oyster and associated epibenthos is important in order to minimize interference during seed collection of target species. The timing and location of seed collection is therefore critical. We also suggest experiments with collectors conditioned with adult Crassostrea gasar shell remnants, as well as those where limited establishment of epibenthos, such as barnacles, has been allowed, in order to maximize spat collection of the target species, C. gasar, along the Pará coast.

As a result of phenotypic plasticity, the cupped oysters (Crassostrea ) are difficult to identify by means of their morphology. However, molecular DNA markers are a useful means of discriminating among these species. Cupped oysters are one of the most widely cultured marine invertebrates and correct species identification is important in aquaculture. Moreover, the molecular phylogeny of the genus Crassostrea and the subfamily Crassostreinae is still not clear. In order to identify the Brazilian cupped oysters and to clarify the phylogenetic relationships of these species, we sequenced a fragment of mitochondrial DNA (16S rRNA gene) from 120 specimens collected at nine different sites distributed along the Brazilian coast. The results identified two native species of oyster: Crassostrea gasar, from the Amazon

Oysters (Ostreidae) manifest a high degree of phenotypic plasticity, whereby morphology is of limited value for species identification and taxonomy. By using molecular data, the aim was to genetically characterize the species of Crassostrea occurring along the Brazilian coast, and phylogenetically relate these to other Crassostrea from different parts of the world. Sequencing of the partial cytochrome oxidase c subunit I gene (COI), revealed a total of three species of Crassostrea at 16 locations along the Brazilian coast. C. gasar was found from Curuçá (Pará state) to Santos (São Paulo state), and C. rhizophorae from Fortim (Ceará state) to Florianópolis (Santa Catarina state), although small individuals of the latter species were also found at Ajuruteua beach (municipality of Bragança, Pará state). An unidentified Crassostrea species was found only on Canela Island, Bragança. Crassostrea gasar and C. rhizophorae grouped with C. virginica, thereby forming a monophyletic Atlantic group, whereas Crassostrea sp. from Canela Island was shown to be more similar to Indo-Pacific oysters, and either arrived in the Atlantic Ocean before the convergence of the Isthmus of Panama or was accidentally brought to Brazil by ship.