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There is growing interest to restore oyster populations and develop oyster reefs for their role in ecosystem health and delivery of ecosystem services. Successful and sustainable oyster restoration efforts largely depend on the availability and selection of suitable sites that can support long-term growth and survival of oysters. Hence, in the present study a habitat suitability index (HSI) model was developed for the intertidal rock oyster (Saccostrea cucullata), with special attention: (1) to the role of the monsoon in the suitability of oyster habitats, and (2) to identify potential suitable sites along the south-eastern Bangladesh coast. Seven habitat factors were used as input variables for the HSI model: (1) water temperature; (2) salinity; (3) dissolved oxygen; (4) particulate inorganic matter (PIM); (5) pH; (6) Chlorophyll-a; and (7) water flow velocity. Seven field surveys were conducted at 80 locations to collect geo-spatial environmental data, which were then used to determine HSI scores using habitat suitability functions. The model results showed that the areas suitable (HSI >0.50) for oyster settlement and growth were characterized by relatively high salinities, Chlorophyll-a, dissolved oxygen and pH values. In contrast, freshwater dominated estuaries and nearby coastal areas with high suspended sediment were found less suitable (HSI <0.50) for oysters. HSI model results were validated with observed oyster distribution data. There was strong correlation between the HSI calculated by the model and observed oyster densities (r = 0.87; n = 53), shell height (r = 0.95; n = 53) and their condition index (r = 0.98; n = 53). The good correspondence with field data enhances the applicability of the HSI model as a quantitative tool for evaluating the quality of a site for oyster restoration and culture. [ABSTRACT FROM AUTHOR]

Abstract Dynamic Energy Budget (DEB) models describe the energy flow in organisms focusing on food assimilation and utilization for maintenance, growth and reproduction. In this paper, specific DEB parameters were obtained for the intertidal rock oyster Saccostrea cucullata , which has culture potential and important ecological functions in estuarine and coastal ecosystems along the Bay of Bengal, Bangladesh. Oyster samples were collected from natural oyster beds and used in a starvation experiment for 20 weeks in the laboratory. A sub-sample of starved oyster was used to record respiration rates and depletion of reserves was recorded by fortnightly measurements of flesh weight. Simultaneously, a group of oysters was used for physiological experiments and growth measurements, required for DEB parameter estimation. Consequently, Arrhenius temperature related parameters (i.e. T A , T L , T H , T AL , and T AH), shape coefficient (δ M), volume specific maintenance rate ( P ̇ M) and volume specific cost for structure ([ E G ]) were estimated using data from the respiration and starvation experiments. An iterative co-variation method was used to estimate the specific DEB parameters using the results of the physiological experiments, field observations and additional literature information. Estimated Arrhenius temperature was 5640 K, which applies between 297 and 305 K. Shape coefficient (δ M = 0.159) was low, compared to other oyster species that characterized the morphology of the oyster. Volume specific maintenance rate ( P ̇ M) was equivalent to 17.99 J cm−3 day−1, while 2377 J cm−3 was estimated as the volume specific cost for structure ([ E G ]). These efforts provide opportunities to apply the DEB model for better understanding the energetics of bivalves under sub-tropical conditions. It is concluded that the hydrometeorological aspects, i.e. a monsoon regime and high turbidity levels, are quite different from temperate regions and drives the physiological traits of shellfish organisms. Highlights • Saccostrea cucullata has culture potential and important ecological functions. • This study establish links between organism's physiology and the environment. • DEB model parameters were estimated under subtropical conditions. • It provides opportunities to apply the DEB model for subtropical oysters. [ABSTRACT FROM AUTHOR]

Abstract: Predation by adult bivalves on bivalve larvae has been suggested to reduce larval abundance in areas with high bivalve filter-feeder biomass. Although the occurrence of larviphagy is well-studied in the laboratory, its effects in the field have scarcely been studied. We studied larviphagy at different spatial scales in the Oosterschelde estuary. On the scale of individuals, we confirmed that larviphagy occurs in Crassostrea gigas and Mytilus edulis in the Oosterschelde estuary, by examining stomach contents of adult bivalves. On a local scale, we studied effects of larviphagy by a Pacific oyster (C. gigas) bed on presence of larvae in the overlying water column by sampling larvae with fixed plankton nets. Abundance of blue mussel (M. edulis) larvae was significantly reduced by the oyster. Abundance of C. gigas larvae did not seem to be reduced by the oyster bed, but spawning by the adult oysters during the sampling period may have affected the results. On estuary-scale, the effect of larviphagy on larval abundance of C. gigas and M. edulis was studied using existing monitoring data over 6 years for M. edulis and 13 years for C. gigas. Numbers of M. edulis larvae showed no significant trend over the 6 years studied. Abundance of C. gigas larvae declined with an increasing filter feeder stock (that was mainly caused by an increase in C. gigas stock). This decline may be due to direct effects of larviphagy or indirect effects such as lowered food levels, and was not compensated by an increased larval production. All results combined, complemented with a theoretical estimate of the effect of larviphagy on estuary-scale, strongly suggest that larviphagy is major source of mortality for bivalve larvae in the Oosterschelde estuary. [Copyright &y& Elsevier]