Growth and distribution of the great scallop (Pecten maximus) in the English Channel: a modelling approach.

The great scallop Pecten maximus is currently the most important species in landings (as well in tons as in value) for the French inshore fleet of the English Channel. A French scientific program “COMANCHE” funded by the French National Research Agency (ANR) was conducted to improve our knowledge on the great scallop within its ecosystem, in an integrated way and over the whole area of the English Channel. In that context, the aim of this study is to better understand the determinism of the growth and distribution of the great scallop in the English Channel, integrating both physical and trophic constraints through a modelling approach. The used method is based on the coupling of a 3D hydrodynamical model (MARS3D developed at Ifremer) providing environmental conditions, a physiological model of scallop individuals and a population model of this species. The bioenergetic model of the individual growth of scallop is based on the dynamic energetic budget (DEB)(Kooijman,1986 J. Theor. Biol. 121, 269–282). There are two environmental forcing variables: the bottom temperature and the food, described as chlorophyll a or as suspended organic/inorganic matter, which were provided by a 3D biogeochemical model of the English Channel (ECOMARS3D). The coupled model allows to calculate the potential of growth in each part of the English channel . Then the best locations for growth are deduced and compare with in-situ data. Moreover this approach let us know where the environmental parameters are favorable enough to allow the survival of P.Maximus. The population model for the scallop, spatialized over the English Channel area, described the whole life cycle (planktonic and benthic) using a mechanistic approach(Savina, M. & Menesguen, A. 2008 Journal of Marine Systems 70 63-76). It is structured in age classes and described the dynamics of the density of each age class. Dispersion of larvae and recruitments of adults are conducted by hydrodynamics...