Simulation of the mollusc Ascoglossa Elysia subornata population dynamics:application to the potential biocontrol of Caulerpa taxifolia growth in the Mediterranean Sea

A multi-modelling simulation was performed to assess the potentialities of a biocontrol of the alga Caulerpa taxifolia (Valhl) C. Agardh by the Ascogl ossa Elysia subornata (Verrill, 1901) in the Mediterranean Sea. With this a im in view, the biological and ecological parameters considered as key fact ors were identified in order to present a state of the art on biological an d ecological parameters related to the behaviour of E. subornata toward C. taxifolia and toward the Mediterranean conditions. To this end, growth, sur vival, reproduction, feeding on C. taxifolia and foraging of E. subornata a re studied. Simulations, taking into account spatial effects, give encourag ing results and show that additional experiments in large mesocosm may be e ngaged to improve the actual knowledge of Elysia behaviour, the impact on C . taxifolia, the trophic relationships, etc. The results of simulations dem onstrate that the greatest impacts on Caulerpa are obtained using either so me adults or mixing adults and juvenile slugs. In any case, better results are obtained by a scattering of slugs on isolated spots rather than on clus ters (with constant surfaces). Lastly, the choice of a suitable date for sc attering increases the weak consumption of Caulerpa resulting from the scat tering of juvenile slugs. (C) 2000 Elsevier Science B.V. All rights reserve d.