Abstract Due to the competition for food, space, oxygen and due to their role as diseases vector, epibionts can negatively affect oyster farming. We assessed the efficacy of six methods commonly used for the removal of epibionts from oyster shells during farming. The experiment was conducted at an oyster farm on the Paraná coast – South Brazil. Oysters (Crassostrea gasar) were acclimated for 90 d in the cultivation system and later exposed to cleaning treatments: i) freshwater; ii) hypersaline water; iii) sodium hypochlorite solution; iv) quaternary ammonia solution; v) exposure to air; vi) hydroblasting; and vii) no cleaning procedure (control). After treatment, oysters were kept in the cultivation system for 15 and 30 d – when the total incrustation and mortality were measured. Epibionts from nine phyla were identified. The most abundant were Arthropoda (Crustacea) (62.5%), Mollusca (33.8%) and Annelida (3.1%). Freshwater [15 (n = 2263 epibionts) and 30 days (n = 2822 epibionts)] and hydroblasting [15 (n = 1850 epibionts) and 30 days (n = 2389 epibionts)] treatments were the most efficient to reduce epibionts and caused lower rates of oyster mortality [15 (5.0 and 3.33%, respectively) and 30 days (1.67 and 6.67%, respectively)].

Abstract In this work, we identified the bacterial microbiota associated with farmed oystersin estuarine regions of four states in the north eastern region of Brazil. During the drought and rainy seasons, for eight months, twenty oysters were sampled seasonally from seven different marine farms. In the laboratory, DNA extraction, amplification, and sequencing of the 16S rRNA gene were performed to establish the taxonomic units. We identified 106 genera of bacteria belonging to 103 families, 70 orders, 39 classes, and 21 phyla. Out of the total, 40 of the genera represented bacteria potentially pathogenic to humans; of these, nine are known to cause foodborne diseases and six are potentially pathogenic to oysters. The most prevalent genera were Mycoplasma, Propionigenium, Psychrilyobacter, and Arcobacter. The results indicate the need for more systematic monitoring of bacteria of the genus Mycoplasma in oyster farming operations in the Brazilian north eastern region. Currently, Mycoplasma is not one of the microorganisms analysed and monitored by order of Brazilian legislation during the oyster production and/or commercialization process, even though this genus was the most prevalent at all sampling points and presents pathogenic potential both for oysters and for consumers.

Resumo O extrativismo descontrolado tem levado a uma redução mundial nos estoques de ostras. Embora o uso de novas e mais eficientes ferramentas que conduzam à redução de impactos ambientais tenham aumentado, a aplicação de tais ferramentas requer conhecimento prévio de características ambientais e biológicas das populações de moluscos bivalves residentes. Dificuldades técnicas são geralmente associadas ao estudo de bancos de ostras submersos e esta dificuldade resulta em uma considerável falta de dados biológicos de ostras que habitam zonas subtidais. Este estudo objetivou pesquisar estoques de Crassostrea brasiliana (sinonímia para C. gasar) em bancos submersos e avaliar um método com o qual as medições de extensão dos bancos, identificação e quantificação das ostras nestes bancos fosse feita usando um sonar de varredura lateral. Este estudo foi conduzido em 10 bancos de ostras localizados na zona de infralitoral da baía de Guaratuba, na costa sul do Brasil. Toda a prospecção dos bancos foi validada por mergulho e amostragens de ostras (n = 20/banco), que foram coletadas para a identificação das espécies por análise molecular. Somente um banco continha ostras que foram genericamente classificadas como Crassostrea sp., enquanto os organismos dos bancos restantes foram identificados como C. brasiliana. A prospecção de bancos revelou a existência de conjuntos de ostras de tamanho variados (média 1,5 m, n = 1.107), espalhados de forma heterogênea no leito dos rios. O número total de ostras em 10 bancos amostrados foi estimado em 21.159,13 ostras ou 1 ostra/4,5 m², o que representou uma baixa densidade para a área de estudo. Os resultados validaram o uso do sonar de varredura lateral como um eficiente mecanismo para a prospecção de ostras localizadas em bancos submersos.

Abstract Uncontrolled extractivism has led to a worldwide reduction in oyster stocks. The use of new and more efficient management tools for impacted environments must increase. The application of such tools requires previous biological and environmental knowledge of the resident populations of these bivalve mollusks. Technical difficulties are usually associated with studies of submerged oyster banks, and these difficulties result in a considerable lack of biological data on the oysters that inhabit subtidal zones. This study aimed to survey Crassostrea brasiliana (also known as C. gasar) stocks in submerged banks and to evaluate a method with which to measure the extent of the banks and identify and quantify the oysters in the banks with the use of side-scan sonar. This study was conducted on 10 oysters banks located in the subtidal zone of Guaratuba Bay, on the south coast of Brazil. The prospection of all these banks was later validated by diving, and oyster samples (n = 20/bank) were collected for species identification with a molecular method. Only one bank contained oysters that were generically classified as Crassostrea sp.; those in the remaining banks being identified as C. brasiliana. The prospected banks contained oysters of various sizes (average 1.5 m, n = 1,107) that were heterogeneously scattered in the riverbeds. The total number of oysters in the 10 sampled banks was estimated to be 21,159.13 oysters or 1 oyster/4.5 m², which represents a low oyster density in the study site. The results validate the use of side-scan sonar as an efficient means with which to prospect for oysters in banks located within subtidal zones.

Among oysters, species of Crassostrea (Sacco, 1897) are the most attractive to aquaculture. In Brazil, the genus is represented by C. rhizophorae (Guilding, 1828) and C. brasiliana (Lamarck, 1819). Because the maturation and breeding technology is not well developed for these species, aquaculturists need a reliable method to decide the correct time to place spat collectors in the field, and to identify both species, which are morphologically similar. In this study a specific Multiplex PCR protocol was developed, using one pair of universal primers from 18S rDNA as a positive control and a pair of specific primers for each target species. The sensitivity and specificity of the protocol was evaluated. It detected C. rhizophorae DNA in low concentrations, and C. brasiliana DNA in even lower concentrations. Further, the Multiplex PCR proved efficient in detecting DNA in concentrations equivalent to that of a single larva of each species, either separated or combined, when mixed with total DNA extract of a plankton sample representing 1000 L of filtered water. Field tests confirmed the applicability of the protocol, which holds the promise to become an important tool for aquaculture or conservation programs, allowing for the continuous monitoring of the life cycle of C. brasiliana and C. rhizophorae, by detecting the right periods of larval release and settlement.