Aurélie Foveau

Modelling larval dispersal of Pecten maximus in the English Channel: a tool for the spatial management of the stocks

The great scallop Pecten maximus supports one of the most important and valuable commercial fisheries around the British Isles and in the northwest of France, but the resource is mainly managed at the scale of each local fishing ground through a combination of European, national and local measures. To analyse the larval dispersal pathways and connectivity patterns among fishing grounds of the great scallop in the Celtic Sea and the English Channel, a particle tracking model was developed. The model combined a 3D physical circulation model that simulated currents and temperature fields and a scallop larval submodel that took into account a temperature-dependent planktonic larval duration and an active vertical swimming behaviour. Due to the lack of stock assessment at the regional scale, the location of the main fishing grounds was established by combining different sources (e.g. grey literature, unpublished scientific surveys, vessel monitoring data, fishermen) while the spawning biomass of each stock was estimated from landings data. Results indicated that each local stock could not be considered as a single independent management unit and that all stocks except that of the Bay of Brest were connected to neighbouring stocks, suggesting that the management should be defined in a metapopulation context. Three major groups of strongly interconnected stocks including two or three stocks exhibiting high retention and self-recruitment rates and some peripheral stocks with a low self-recruitment rate were defined: the North Brittany and Channel Islands, the eastern English Channel, and the SW of England. Our results were discussed in terms of the definition of management units in comparison with genetic and phenotypic data, and in terms of resource management in a transnational context.

Process-driven and biological characterisation and mapping of seabed habitats sensitive to trawling

The increase of anthropogenic pressures on the marine environment together with the necessity of a sustainable management of marine living resources have underlined the need to map and model coastal environments, particularly for the purposes of spatial planning and for the implementation of integrated ecosystem-based management approach. The present study compares outputs of a process-driven benthic habitat sensitivity (PDS) model to the structure, composition and distribution of benthic invertebrates in the Eastern English Channel and southern part of the North Sea. Trawl disturbance indicators (TDI) computed from species biological traits and benthic community composition were produced from samples collected with a bottom trawl. The TDI was found to be highly correlated to the PDS further validating the latter’s purpose to identify natural process-driven pattern of sensitivity. PDS was found to reflect an environmental potential that may no longer be fully observable in the field and difference with in situ biological observations could be partially explained by the spatial distribution of fishery pressure on the seafloor. The management implication of these findings are discussed and we suggest that, used in conjunction with TDI approaches, PDS may help monitor management effort by evaluating the difference between the current state and the presumed optimal environmental status of marine benthic habitats.

Using Underwater Imagery as a Complementary Tool for Benthos Sampling in an Area with High-Energy Hydrodynamic Conditions

Using Underwater Imagery as a Complementary Tool for Benthos Sampling in an Area with High- Energy Hydrodynamic Conditions Underwater imagery is increasingly being used in the description of communities and habitats, as a tool to aid in the designation and management of marine protected areas. Here, we developed an underwater imagery system to monitor the seafloor and benthic communities in the Raz Blanchard (Aldernez Race), an area in the English Channel characterized by high-energy hydrodynamics. Despite the difficult conditions of acquisition, the underwater images highlighted the heterogeneous nature of the seabed in the Raz Blanchard. In this way, underwater imagery is a useful tool in providing additional information to standard benthic observations, particularly for the description of sessile epifauna and benthic landscapes. This system is flexible, robust and simple enough to be used in coastal and offshore areas, and is suitable as a complementary tool in benthic surveys to monitor the status and changing trends of seabed fauna and could be applied in future surveys.