The Dynamic Energy Budget (DEB) model (Kooijman, S.A.L.M., 1986. Energy budgets can explain body size relations. pp.) has been adapted to describe the dynamics of growth and reproduction of the Pacific oyster (Crassostrea gigas) reared in different areas under conditions ranging from controlled to natural. The values of the model parameters were estimated from available physiological data and from published information. The sets of data used to validate the model came from three long-term growth experiments (> 5 months) performed on Pacific oysters reared under different conditions of food and environment. The forcing variables were temperature and phytoplankton densities, the latter being assessed from in vivo fluorescence and chlorophyll-a concentration measurement. The successful validation of the model on the three data sets demonstrated its ability to capture the dynamics of the energy budget in the Pacific oyster in various environments with the same set of parameters. The only parameter that varied between simulations was the half-saturation coefficient (XK), because of a different diet composition between the three environments under test. The model successfully reproduced quantitatively the growth and reproduction and the timing of spawning. These first simulation data led us to propose several promising perspectives of application for this model in shellfish ecosystems.

The high degree of physical factors in intertidal estuarine ecosystem increases material processing between benthic and pelagic compartments. In these ecosystems, microphytobenthos resuspension is a major phenomenon since its contribution to higher trophic levels can be highly significant. Understanding the sediment and associated microphytobenthos resuspension and its fate in the water column is indispensable for measuring the food available to benthic and pelagic food webs. To identify and hierarchize the physical/biological factors potentially involved in MPB resuspension, the entire intertidal area and surrounding water column of an estuarine ecosystem, the Bay des Veys, was sampled during ebb tide. A wide range of physical parameters (hydrodynamic regime, grain size of the sediment, and suspended matter) and biological parameters (flora and fauna assemblages, chlorophyll) were analyzed to characterize benthic-pelagic coupling at the bay scale. Samples were collected in two contrasted periods, spring and late summer, to assess the impact of forcing variables on benthic-pelagic coupling. A mapping approach using kriging interpolation enabled us to overlay benthic and pelagic maps of physical and biological variables, for both hydrological conditions and trophic indicators. Pelagic Chl a concentration was the best predictor explaining the suspension-feeders spatial distribution. Our results also suggest a perennial spatio-temporal structure of both benthic and pelagic compartments in the ecosystem, at least when the system is not imposed to intense wind, with MPB distribution controlled by both grain size and bathymetry. The benthic component appeared to control the pelagic one via resuspension phenomena at the scale of the bay. Co-inertia analysis showed closer benthic-pelagic coupling between the variables in spring. The higher MPB biomass observed in summer suggests a higher contribution to filter-feeders diets, indicating a higher resuspension effect in summer than in spring, in turn suggesting an important role of macrofauna bioturbation and filter feeding (Cerastoderma edule).

Growth of the black-lip pearl oyster, Pinctada margaritifera var. cumingi, was studied for an annual cycle, from March 1997 to April 1998, in the lagoon of Takapoto atoll (Tuamotu archipelago, French Polynesia). Growth in shell and in tissue were measured every 15 days on three successive age groups of cultivated pearl oysters. At the same time, hydrobiological parameters (temperature, salinity, oxygen concentration, suspended particulate matter), known to have influence on bivalve growth, were followed each week during culture. No seasonal trend was observed in hydrobiological parameters, except for temperature which varied between 26°C and 31°C. The potential food for pearl oysters (particulate organic matter, POM, mg l −1) was slightly concentrated, but always available, so that, in this lagoon environment, no period seemed to be unfavourable to pearl oyster growth. Effectively, growth in shell was regular and shell did not exhibit any annual ring. Nevertheless, as it is often the case for bivalves, shell growth showed a progressive decrease with the age of pearl oyster and followed a classical Von Bertalanffy model: H=160.5 (1−e −0.038 (t−3.73)) with H the shell height (in mm) and t the age (in months). On the other side, growth in tissue did not follow the same pattern than for shell: P. margaritifera exhibited reduced growth rate in tissue during the warm season (November-April) so that a seasonal growth model was more appropriate: W tissue =6.9/(1+e (5.58-0.208 t−0.435 sin (2π/12 (t−1.427)) with W tissue , the dry tissue weight (in g) and t the age (in months). Several results concerning growth rates should be of interest for pearl farming. Firstly, the progressive decrease measured in shell growth rate implies, for pearl seeding operations, that the sooner the nucleus is implanted, the greater is the rate of nacreous deposition on this nucleus, and shorter is the time to obtain a marketable pearl for farmers. Secondly, exhaustive comparison, between growth rates obtained in our study and those obtained in other lagoons, tended to demonstrate that there is a small but significant variability in growth between lagoons of the Tuamotu archipelago. Further investigations need to be engaged in order to determine the most suitable sites for pearl farming in French Polynesia. Finally, comparison between growth of P. margaritifera var. cumingi and growth of other pearl oysters showed that P. maxima but also P. margaritifera var. erythraensis would also exhibit fast growth in Polynesian waters and then, would constitute potential candidates for further Polynesian diversification projects.

Marine aquaculture is the most promising industry for ensuring future provision of seafood. Yet, the worldwide growth and expansion of this industry have been slower than expected, calling for the identification of environmentally suitable sites while accounting for all factors that could constrain or benefit its establishment. Here, we determine the main obstacles and risks hindering the growth and expansion of marine aquaculture, as well as the needs and recommendations to overcome such constraints. Our analysis is based on results obtained from a consultation process held in 16 study sites located around the world with the participation of 614 stakeholders representing the research community, aquaculture industry, government, conservation groups, and education and fishermen associations. A high level of commonality exists in the main issues hindering aquaculture growth and expansion in coastal, off‐the‐coast and offshore aquaculture with most being attributed to interactions with other maritime activities, including conflicts with other users and administrative procedures, including licensing. Critical needs for improved management and expansion of the aquaculture industry are related to planning and management of developments and technological advances, with economic and market needs featuring to a lesser extent. Key procedures recommended to assist further aquaculture growth are the standardisation and simplification of regulatory frameworks, improvement of governance, and the adoption of participatory processes to facilitate meaningful and productive stakeholder engagement. We strongly recommend stakeholder participation to enhance insights on the full environmental and human dimensions of marine management and for implementation of ecosystem‐based marine spatial planning.

Intertidal flats of the estuarine macro-intertidal Baie des Veys (France) were investigated to identify spatial features of sediment and microphytobenthos (MPB) in April 2003. Gradients occurred within the domain, and patches were identified close to vegetated areas or within the oyster-farming areas where calm physical conditions and biodeposition altered the sediment and MPB landscapes. Spatial patterns of chl a content were explained primarily by the influence of sediment features, while bed elevation and compaction brought only minor insights into MPB distribution regulation. The smaller size of MPB patches compared to silt patches revealed the interplay between physical structure defining the sediment landscape, the biotic patches that they contain, and that median grain-size is the most important parameter in explaining the spatial pattern of MPB. Small-scale temporal dynamics of sediment chl a content and grain-size distribution were surveyed in parallel during 2 periods of 14 d to detect tidal and seasonal variations. Our results showed a weak relationship between mud fraction and MPB biomass in March, and this relationship fully disappeared in July. Tidal exposure was the most important parameter in explaining the summer temporal dynamics of MPB. This study reveals the general importance of bed elevation and tidal exposure in muddy habitats and that silt content was a prime governing physical factor in winter. Biostabilisation processes seemed to behave only as secondary factors that could only amplify the initial silt accumulation in summer rather than primary factors explaining spatial or long-term trends of sediment changes. KEY WORDS: Benthic diatoms · Benthos · Coastal ecosystems · Intertidal flats · Baie des Veys · Normandie · Spatial pattern · Geostatistics · KrigingResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 458: 53-68, 2012 Kronkamp 1999, Perissinotto et al. 2003). Dynamics of marine systems vary widely in their temporal and spatial components due to complexity in the benthopelagic coupling (Zajac 2008). The trophic environment of benthic fauna in these systems is therefore characterised by a high degree of spatial heterogeneity, such as transition zones and patches (Deegan & Garritt 1997, Dubois et al. 2007) that are related to the landscape of their habitats. It appears very relevant to understand the spatial patterns of primary producers in relation to sediment in order to elucidate the role they play in the trophic food web and to assess the respective contributions of both components to consumer's diet (Lefebvre et al. 2009). The questions of spatial distribution of benthic primary producer are thus critical to gain new insights in the dynamics and structure of macrozoobenthos that inhabit these environments (Herman et al. 2000).There is a general consensus that MPB biomass varies along wide-scale environmental gradients and is not affected by an isolated variable but, rather, depends on a combination of factors controlling ...

We successfully tested a Dynamic Energy Budget (DEB) model of the oyster Crassostrea gigas using published environmental data and growth data collected in Thau lagoon (France). Estimates of most DEB parameters were based on independent datasets and only two parameters were calibrated using our datasets: the shape parameter, which was used to convert body volume into shell length, and the half-saturation coefficient, which controlled the functional response of assimilation to food concentration, represented by chlorophyll-a concentration. The DEB model proved to be robust and generic: it was able to reproduce oyster growth in Thau lagoon and other ecosystems. We also assessed population dynamics by coupling DEB equations and an Individual Based Model (IBM) of cultivated oyster populations. The results were compared with previously published simulations of harvested production and standing stock based on an empirical growth equation and a partial differential equation of population dynamics. Differences between the two studies were explained by the difference between the predictions of oyster growth with the empirical and the DEB models. We also accounted for growth variability between individuals and showed that IBM offers a powerful alternative to continuous equations when several physiological variables are involved.

No abstract

Many studies based on bioenergetics growth models have investigated the effects of environmental factors on oyster (Crassostrea gigas) growth and physiology. However, most of these models are site-specific and cannot be app lied to other culture sites without the re-estimation of parameters or re-formulation of some processes. We aimed to develop a gen eric growth model suitable for application in contrasting environments, with a constant set of parameters. We tested the oyster-DEB model (Bourlès et al. 2009) for the stimulation of C. gigas growth in different cohorts (spats and adults) at major shellfish culture sites in