Gametogenic cycle of Crassostrea gigas in contrasting Mediterranean habitats: marine (Gulf of Tunis) and continental (Bizert lagoon) culture sites.

Effect of temperature on gonadal growth and maturation of Paracentrotus lividus (Lamarck, 1816)

The aquaculture of Pacific or Japanese oyster (Crassostrea gigas) culture in Chile has been developed for almost five decades. Today, it is the most widely cultivated mollusk on the planet, given its introduction in more than 60 countries to produce high-quality protein. The Pacific oyster shows rapid growth in aquaculture production strategies in Chile. Pacific oyster farming is carried out along the entire coast of Chile, being a consolidated productive activity of economic interest in the southern part. By the end of the 1990s, the appearance of norovirus depressed its production, and some small-scale aquaculture producers currently sell their oyster production on the beach. Despite its extensive production, Chile has a significant information gap regarding this resource. This review addresses this gap and examines oyster culture in Chile, emphasizing the introduction stage of the species, production stages, culture methods, diseases, and regulatory, commercial, and social implications. Future challenges for Pacific oyster aquaculture include the production of juveniles in hatcheries to support aquaculture farmers and consolidate this species for the diversification of aquaculture in some coastal areas of Chile under conditions of productive management, simple technologies, and low initial investment. Conditions for the development of small-scale aquaculture systems. Finally, strengthening marketing actions will enable aquaculture farmers to move from a national scenario to the current demand in international markets.

Pacific oyster (Crassostrea gigas) farming has developed in recent years along the Italian coasts of the Adriatic sea. This is particularly true in sites located in the northern area and only recently becoming more common in the southern area, which is different particularly in regards to temperature and trophic conditions. There is a lack of studies on the status of the oysters farmed in this area; therefore, the present research aimed to monitor the health conditions of adult triploid oysters that were kept in offshore longline culture system over one year. Environmental parameters were daily estimated from satellite. Biometric, immunological and oxidative stress parameters were measured monthly, looking also for the presence of pathogens, such as OsHV-1, Vibrio aestuarianus and Vibrio splendidus. During summer months, high temperatures and low food availability had a detrimental impact on the growth and immunological parameters which showed a progressive recovery during the autumn and winter months. Overall, no abnormal mortality was observed, and no histological alterations were evident. The presence of pathogens was negligible, and the oxidative stress parameters were poorly detected, except for the digestive glands during the autumn and winter seasons. On this basis, the data herein reported suggest that the area could be suitable for the development of triploid Pacific oyster farming, although animals would require a longer time to reach commercial size.

The holothuroid spawning can be succesful depend on varoius factors such as salinity, temperature, primary productivity and other physiological adaptation toward environment influences. The salinity fluctuation is one of the environment factors, which influence and can cause various osmotic pressure of coelomic fluid of Holothoroid and also gonad maturity stage. Holothuroid (sea cucumber), Paracaudina australis, is overexploited in Kenjeran waters, Surabaya, East Java. The study was aimed to reveal relationship between gonad maturity stage and level of osmotic work of sea cucumber P. australis. Fifty samples of P. australis were collected monthly. Coelomic fluid samples of approximately 200–1000 µl were obtained from all samples using disposable insulin syringes. There were 37 holothuroids classified in the late maturity (stage 5), 74 holothuroid in the earlier maturity stage (stage 1). Gonad maturity stage 5 (late maturity) could be reached on December 2016. Contrasly, the gonad maturity stage 1 (earlier maturity) was found on August 2016. The analysis of coelomic fluid showed that the average value of level of osmotic work ranged 70 to 91 mOsm/L H2O in the earlier gonad maturity stage. Contrasly, in the late maturity, the average value of level of osmotic work ranged 118 to 156 mOsm/L H2O. There is relationship between gonad maturation stage and level of osmotic work. From stage of gonad maturity 1 to 5, there were upward trend level of osmotic work in coelomic fluid of P. australis. Keywords: gonad maturity, osmotic, Paracaudina australis

Variations in biochemical composition and lipid classes in relations to the gametogenic cycle were studied in digestive gland, labial palps and gonad in the Pacific oyster Crassostrea gigas from the Western Atlantic coast of France over 1 y. Variations in the weight of the soft body parts, gonad development and spawning depended on environmental conditions, mainly on nutrients availability. The main energy reserve is the glycogen, showing a marked seasonal variability in all tissues studied this component increased in the digestive gland during the phytoplankton blooms and was rapidly transferred and accumulated in labial palps and gonad during stages IIID-0; glycogen was then mobilized during the final stage of somatic growth and during the beginning of the gametogenic cycle (stage IA). Glycogen is consumed almost totally at the beginning of spring, coinciding with an important increase of phospholipids in males and triacylglycerols in females. This fact seems to indicate that the glycogen reserves were used in the synthesis of lipids and in supporting the high energy demand existing during the active vitellogenesis and spermatogenesis. The digestive gland, besides playing an intermediary role in transferring the ingested lipids to other organs, seems to constitute an important organ of reserve of lipids, mobilizing phospholipids in winter towards palps and gonad during the somatic growth, but also during the initial gametogenesis and sexual maturation (triacylglicerols). There is depletion in the reserves of glycogen and triacylglicerols of the labial palps during the last stage of gonadal maturation. Simultaneously, an increase in triacylglicerols in gonad occurs, suggesting that the labial palps were an organ of reserve to sustain the most advanced stages of gonadal ripeness. The changes of sterol esters of gonad are discussed with regard to gametogenic cycle of Crassostrea gigas.

Bacteria from the family Vibrionaceae have been implicated in mass mortalities of farmed Pacific oysters (Magallana gigas) in multiple countries, leading to substantial impairment of growth in the sector. In Ireland there has been concern that Vibrio have been involved in serious summer outbreaks. There is evidence that Vibrio aestuarianus is increasingly becoming the main pathogen of concern for the Pacific oyster industry in Ireland. While bacteria belonging to the Vibrio splendidus clade are also detected frequently in mortality episodes, their role in the outbreaks of summer mortality is not well understood. To identify and characterize strains involved in these outbreaks, 43 Vibrio isolates were recovered from Pacific oyster summer mass mortality episodes in Ireland from 2008 to 2015 and these were whole-genome sequenced. Among these, 25 were found to be V. aestuarianus (implicated in disease) and 18 were members of the V. splendidus species complex (role in disease undetermined). Two distinct clades of V. aestuarianus - clade A and clade B - were found that had previously been described as circulating within French oyster culture. The high degree of similarity between the Irish and French V. aestuarianus isolates points to translocation of the pathogen between Europe's two major oyster-producing countries, probably via trade in spat and other age classes. V. splendidus isolates were more diverse, but the data reveal a single clone of this species that has spread across oyster farms in Ireland. This underscores that Vibrio could be transmitted readily across oyster farms. The presence of V. aestuarianus clades A and B in not only France but also Ireland adds weight to growing concern that this pathogen is spreading and impacting Pacific oyster production within Europe.

Pacific oyster (Crassostrea gigas) is an invasive species which is able to adapt a wide range of environmental conditions. The study was conducted from August to October 2014. Objective of this study was to asses the distribution pattern, condition and gonad maturity length (Lm 50%) of the Pacific oysters in mangrove ecosystem of Cimanuk Delta, Indramayu, West Java, Indonesia. This study was conducted in two adjacent areas: Pabean Ilir and Pagirikan subdeltas. The oysters were collected from the estuary, brackish water ponds and the coastal flat, and observed for their abundance, total length (mm) and weight (g). Morphological and histological methods were used to estimate the gonad maturity stage. Analysis were carried out to estimate distribution pattern and condition factor. According to the study, the Pacific oyster distribution pattern was clumped. The condition factor of the oyster was higher in the brackish water pond and estuary than in the coastal flat. The Pacific oyster was found in gonad maturity stage (GMS) I – IV. The oyster was hermaprodit protandry and had length maturity (Lm 50%) of 47,46-48,43 mm (male) and 75,27-75,50 mm (female).

Vibrio species have been associated with recurrent mass mortalities of juvenile oysters Crassostrea gigas threatening oyster farming worldwide. However, knowledge of the ecology of pathogens in affected oyster farming areas remains scarce. Specifically, there are no data regarding (i) the environmental reservoirs of Vibrio populations pathogenic to oysters, (ii) the environmental factors favoring their transmission, and (iii) the influence of oyster farming on the persistence of those pathogens. This knowledge gap limits our capacity to predict and mitigate disease occurrence. To address these issues, we monitored Vibrio species potentially pathogenic to C. gigas in 2013 and 2014 in the Thau Lagoon, a major oyster farming region in the coastal French Mediterranean. Sampling stations were chosen inside and outside oyster farms. Abundance and composition of phyto-, microzoo-, and mesozooplankton communities were measured monthly. The spatial and temporal dynamics of plankton and Vibrio species were compared, and positive correlations between plankton species and vibrios were verified by qPCR on isolated specimens of plankton. Vibrio crassostreae was present in the water column over both years, whereas Vibrio tasmaniensis was mostly found in 2013 and Vibrio aestuarianus was never detected. Moreover, V. tasmaniensis and V. crassostreae were found both as free-living or plankton-attached vibrios 1 month after spring mortalities of the oyster juveniles. Overall, V. crassostreae was associated with temperature and plankton composition, whereas V. tasmaniensis correlated with plankton composition only. The abundance of Vibrio species in the water column was similar inside and outside oyster farms, suggesting important spatial dispersion of pathogens in surrounding areas. Remarkably, a major increase in V. tasmaniensis and V. crassostreae was measured in the sediment of oyster farms during cold months. Thus, a winter reservoir of pathogenic vibrios could contribute to their ecology in this Mediterranean shellfish farming ecosystem.

Abstract. Coastal warming, acidification, and deoxygenation are progressing primarily due to the increase in anthropogenic CO2. Coastal acidification has been reported to have effects that are anticipated to become more severe as acidification progresses, including inhibiting the formation of shells of calcifying organisms such as shellfish, which include Pacific oysters (Crassostrea gigas), one of the most important aquaculture resources in Japan. Moreover, there is concern regarding the combined impacts of coastal warming, acidification, and deoxygenation on Pacific oysters. However, spatiotemporal variations in acidification and deoxygenation indicators such as pH, the aragonite saturation state (Ωarag), and dissolved oxygen have not been observed and projected in oceanic Pacific oyster farms in Japan. To assess the present impacts and project future impacts of coastal warming, acidification, and deoxygenation on Pacific oysters, we performed continuous in situ monitoring, numerical modeling, and microscopic examination of Pacific oyster larvae in the Hinase area of Okayama Prefecture and Shizugawa Bay in Miyagi Prefecture, Japan, both of which are famous for their Pacific oyster farms. Our monitoring results first found Ωarag values lower than the critical level of acidification for Pacific oyster larvae in Hinase, although no impact of acidification on larvae was identified by microscopic examination. Our modeling results suggest that Pacific oyster larvae are anticipated to be affected more seriously by the combined impacts of coastal warming and acidification, with lower pH and Ωarag values and a prolonged spawning period, which may shorten the oyster shipping period and lower the quality of oysters.

Vibrio aestuarianus is frequently found in coastal areas and can infect and induce mortalities in the pacific oyster Crassostrea gigas. However, nothing is known about its distribution and seasonality in the estuarine environment, especially where oyster farming is practiced. Its occurrence was investigated in sediment and oyster haemolymph at 2 oyster farms in Brittany (France) over 2 yr during 2 periods, from June to September 2007 and from February to June 2008. Total heterotrophic bacteria (HB) were cultured on marine agar while total Vibrio spp. and V aestuarianus were selectively numerated using thiosulfate citrate bile salts sucrose agar (TCBS agar) and the species-specific hybridisation method, respectively. PCR was performed to detect V aestuarianus in sediment when it became unculturable. Both total Vibrio spp. and V aestuarianus had a seasonal trend. The highest concentrations were recovered in the warmest months. Its abundance ranged from 10(2) to 4 x 10(5) CFU ml(-1) in haemolymph and from 10(3) to 1 x 10(4) CFU g(-1) in the sediment. Temperature was the main factor influencing the concentration of Vibrio spp. and V. aestuarianus in the sediment. Thus V aestuarianus might subsist during the cold seasons in the sediment, from which it can emerge when environmental conditions became favourable.

The Soft-Shell Clam Mya arenaria (Linnaeus) in North America. The Oyster Fishery of Eastern North America Based on Crassostrea virginica. Cultural Practices and Production of the American Oyster, with Emphasis on the South Atlantic and Gulf of Mexico. The European Oyster, Ostrea edulis L., in Maine, U.S.A., and Eastern Canada. Quahog Clams in the United States. Mussel Aquaculture in Marine and Estuarine Environments Throughout the World. Culture of Hinnites and Related Scallops on the American Pacific Coast. Culture of Crassostrea corteziensis in Mexico. Biology and Culture of the Caribbean or Mangrove Oyster, Crassostrea rhizophorae (Guilding), in the Caribbean and South America. Crassostrea rhizophorea (Guilding) and C. brasiliana (Lamarck) in South and Central America. Chilean Mussel Culture Mytilus edulis chilensis (Hupe, 1854) Choromytilus chorus (Molina, 1782) Aulacomya ater (Molina, 1782). Cultivation of the Chilean Oyster, Tiostrea chilensis (Philippi, 1845). Oyster Culture in European Countries. Mussels in India. Oysters in India. Patinopecten (Mizuhopecten) yessoensis (Jay) in Japan. Oyster Culture in Japan and Adjacent Countries: Crassostrea gigas (Thunberg). The Pearl Oyster, Pinctada Fucata (Gould) (Family Pteriidaea) The Culture of Marine Bivalve Mollusks in China. Culture of Farrer's Scallop, Chlamys Farreri (Jones and Preston) in China. Mariculture of Giant Clams. The Green Mussel (Perna viridis) in the Philippines. The Slipper-Shaped Oyster (Crassostrea iredalei) in the Philippines. The Pacific Oyster, Crassostrea gigas, in Australia. New Zealand Scallops, Pecten novaezelandiae Reeve. Perna canaliculus (Gmelin) in New Zealand. The Northern Rock Oyster, Saccostrea glomerata (Gould, 1850), in New Zealand. The Pacific Oyster, Crassostrea gigas (Thunberg, 1793), in New Zealand. Index.

Due to the oil spill incident in December 2007, every facility of oyster culture was removed in western coast especially in Taean and Seosan. To restore oyster resources in Taean and Seosan, we brought oyster seeds from southern area and monitored their growth. In addition we monitored the culture environment throughout the year, and observed the number of oyster larvae and attached spats on collectors during summer. The factors of water environment were appropriate for oyster culture in both study area. The growth of shell height was larger in Uihang-ri, Taean than Jungwang-ri, Seosan. Spawning was more intensive in a short time in Jungwang-ri, Seosan than Uihang-ri, Taean. The number of oyster larvae and spats of collectors were much more in Jungwang-ri, Seosan than Uihang-ri, Taean. This study showed that transplantation of healthy oyster seeds from southern area can be a way of restoration of oyster resources in western coast. In addition, systematic approaches are necessary by building a better understanding of regional characteristics to restore and enlarge the oyster culture farms in western coast. In summary Uihang-ri, Taean will be appropriate for cultivation farms and Jungwang-ri, Seosan for seedling grounds to increase oyster culture productivity. Key word; oyster, Crassostrea gigas, growth, larvae, spat, restoration, transplantation

The presence of bivalves and bivalve aquaculture can have positive and negative impacts on seagrass and associated benthic communities. Some oyster (Crassostrea gigas) aquaculture methods recently have been restricted to reduce benthic disturbance and protect native eelgrass (Zostera marina) in West coast (USA) estuaries. We argue that aquaculture, like all food production systems, involves tradeoffs with natural systems, but that the magnitude of those tradeoffs depends on the ecological details of the production system. Capitalizing on oyster aquaculture farms as large scale ''manipulations'' in Willapa Bay, WA (USA), we explored three different oyster aquaculture methods (mechanical harvest or ''dredged'' on-bottom, hand picked on-bottom and long line off-bottom). We found that both the biological (oyster-eelgrass interactions) and physical (disturbance or structure) components of aquaculture led to changes in the eelgrass population. Eelgrass density declined with oyster density in all aquaculture areas, likely as a result of direct competition for space. Eelgrass relative growth rate, plant size, and production did not change with oyster density. However, all eelgrass measures were affected by aquaculture, and the type and magnitude of impacts varied among eelgrass measures and aquaculture methods. Throughout the bay, eelgrass in long line areas occurred at densities indistinguishable from nearby uncultivated areas, but in 2004, eelgrass in long line areas was smaller (32%) and had lower production per area (70%). Cultivating oysters in dredged or hand picked beds increased eelgrass growth rates slightly, but led to lower eelgrass density (70% and 30%, respectively), plant size (32%, both cases), and production (70%, both cases). In a large scale simulated mechanical harvest experiment, the temporal response of eelgrass density varied dramatically by site, ranging from 1 to >4 y. If eelgrass impact reduction, rather than avoidance, is identified as the management goal, the degree of tradeoff between eelgrass habitat and oyster production can be minimized by managing aquaculture methods or oyster planting densities, depending on the eelgrass measure of interest. Explicit management goals and appropriate eelgrass habitat indicators must be developed before our findings can be used to suggest best management practices for intertidal aquaculture in the Pacific Northwest.

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 276:103-113 (2004) - doi:10.3354/meps276103 Influence of suspended oyster cultures on nitrogen regeneration in a coastal lagoon (Thau, France) Nabila Mazouni* Cépralmar, 20 rue République, 34000 Montpellier, France *Email: mazouni@cepralmar.org ABSTRACT: The present study was designed to quantify the potential influence of oyster cultures (Crassostrea gigas, Thunberg) on dissolved inorganic nitrogen (DIN) renewal in a shallow coastal lagoon (Thau, France), where nitrogen is the factor limiting primary production. The approach was based on a comparative in situ analysis of the seasonal patterns of nitrogenous nutrient exchanges at both the water sediment and oyster cultures water interfaces. The experiments were performed at a station under the influence of oyster cultures (UC) compared with benthic exchanges in a station outside their direct influence (OC) which was used as the reference site for benthic fluxes. In contrast to what it is usually reported for shallow ecosystems, I found evidence of a key influence of suspended oyster culture units (OCU) on the regeneration in the water column of nitrogen available to the phytoplankton, with benthic remineralisation being only of secondary importance. The results also showed that the greatest impact of oyster cultures was on DIN renewal (e.g. nitrogen transformation) in the water column, not on particulate organic nitrogen transfer to the sediment. In the sector studied, it also appeared that nitrogen recycling by both sediments and OCU could satisfy the nitrogen requirements of the primary producers except in summer when other internal nitrogen sources were necessary. Conversely, during most seasons, pelagic primary production could not meet the demand for particulate organic nitrogen of the cultured assemblages (oysters and epibiota). This emphasises the importance to the diet of cultured assemblages of other nitrogen sources such as heterotrophic populations of bacteria, cillates or flagellates. KEY WORDS: Oyster culture · Sediment interface · Nitrogen budget · Fluxes · Lagoon Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 276. Online publication date: August 02, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Resolution of the controversial relationship between Pacific and Portuguese oysters internationally and in Vietnam