A comparative ecophysiological study was carried out in September and November 2002 for two bivalves, Paphia rhomboïdes and Glycymeris glycymeris, which are significantly harvested in the Western Channel (French coast). Individual measurements of clearance and respiration rates were performed for both species, in several experimental conditions of temperature and phytoplankton concentrations. Those conditions were chosen to be in the range of those commonly observed in the subtidal area of the Western Channel. The mean value of clearance rate and oxygen consumption obtained from continuous data recording did not reveal any significant influence of temperature in the investigated range, but a significant difference between P. rhomboïdes and G. glycymeris. P. rhomboïdes showed a continuous feeding activity and faeces production and was characterised by high clearance rate (mean=1.7 l h −1 g −1 ) regulated by the phytoplankton concentration and high assimilation efficiency (approximately 90%). On the opposite, G. glycymeris showed a periodic feeding activity and faeces production with low clearance rates independent of phytoplankton concentration (mean=0.4 l h −1 g −1 ) and a lower assimilation efficiency (approximately 78%). Individual SFG values were calculated for both species and it appears that P. rhomboïdes exhibited higher SFG values than G. glycymeris, except for low concentration of algae. These results may help to explain the significant difference in growth rate of both species. However, assumptions are made on differences in food source and/or feeding behaviour of P. rhomboïdes and G. glycymeris

No abstract

Exploited coastal-nursery-dependent fish species are subject to various stressors occurring at specific stages of the life cycle: climate-driven variability in hydrography determines the success of the first eggs/larvae stages; coastal nursery habitat suitability controls juvenile growth and survival; and fisheries target mostly adults. A life cycle approach was used to quantify the relative influence of these stressors on the Eastern English Channel (EEC) population of the common sole (Solea solea), a coastal-nurserydependent flatfish population which sustains important fisheries. The common sole has a complex life cycle: after eggs hatch, larvae spend several weeks drifting in open water. Survivors go on to metamorphose into benthic fish. Juveniles spend the first two years of their life in coastal and estuarine nurseries. Close to maturation, they migrate to deeper areas, where different subpopulations supplied by different nurseries reproduce and are exploited by fisheries. A spatially structured age-and stagebased hierarchical Bayesian model integrating various aspects of ecological knowledge, data sources and expert knowledge was built to quantitatively describe this complex life cycle. The model included the low connectivity among three subpopulations in the EEC, the influence of hydrographic variability, the availability of suitable juvenile habitat and fisheries. Scenarios were designed to quantify the effects of interacting stressors on population renewal. Results emphasized the importance of coastal nursery habitat availability and quality for the population renewal. Realistic restoration scenarios of the highly degraded Seine estuary produced a two-third increase in catch potential for the adjacent subpopulation. Fisheries, however, remained the main source of population depletion. Setting fishing mortality to the maximum sustainable yield led to substantial increases in biomass (+100%) and catch (+33%) at the EEC scale. The approach also showed how climate-driven variability in hydrography is likely to interact with human pressures, e.g., overfishing increased the sensitivity to unfavorable conditions. Our results provided insights into the dynamics of numerous exploited coastal-nursery-dependent species while paving the way toward more robust advice for sustainable management of these resources.

Quantifying connectivity within fish metapopulations is an important component in understanding population dynamics and providing an evidence base for assessment and management. We investigate metapopulation connectivity of the common sole (Solea solea) in the Eastern English Channel (EEC). The EEC common sole stock is currently assessed as a single and spatially homogeneous population, but connectivity induced through adult movements within this stock and with nearby stocks remains unknown. To fill this knowledge gap, we developed a state-space mark–recovery model, designed to estimate adult connectivity using mark–recapture data from multiple release experiments from 1970 to 2018 across the EEC and adjacent management areas. The model estimates seasonal fish movements between five predefined areas, Western English Channel, Eastern English Channel (split into three discrete sub-areas), and North Sea. Over 32 000 fish were tagged, 4036 of which were recovered via fisheries. Our results suggest minimal large-scale adult movements between these areas; movements among spatial units within the EEC were very low with even lower levels of immigration from areas adjoining the EEC. Our results support the hypothesis of segregated populations within the EEC. The importance of accommodating population substructure in the fisheries management is considered.

Ecosystem models can be used to understand the cumulative impacts of human pressures and environmental drivers on ecosystem structure and dynamics. Predictive modeling can show how management can influence those dynamics and structures and the ecosystem services these systems provide. Many nations and intergovernmental organizations are advocating for ecosystem-based management, often with a specific emphasis to evaluate various future management strategies. Atlantis is an end-to-end ecosystem model that is well suited for this task and has so far been developed for more than 30 diverse marine ecosystems worldwide. To provide a better understanding of the current modeling work, elicit wider interest, and foster collaboration within the Atlantis community, the first international Atlantis Summit was convened in December 2015. The main outcomes from this workshop included a clearer framework and infrastructure for model development and collaboration; the opportunity to perform common scenarios with a range of Atlantis models to analyze ecosystem Highlights ► First International Atlantis Ecosystem Modeling Workshop convened in December 2015. ► It provided an overview of current Atlantis modeling work and fostered collaboration. ► Atlantis applications have matured as have ecosystem models for use in marine EBM.