Scallop spat are produced under intensive culture conditions. A frequently encountered bottleneck in this process has been the mass mortalities of larvae observed if antibiotics are not added to the culture system. This is indicative of sub-optimal larval rearing conditions. The culture conditions currently in use include numerous factors that may affect growth and survival: physical, chemical, and biological, as well as the interaction between these determined by the production method or design. Our most recent work on larval rearing systems has underscored the lack of basic knowledge about scallop (Pecten maximus L.) larval biology. This knowledge is needed to provide the larvae with optimum conditions for growth and survival, i.e. to ensure the best q uality of the larvae produced. The proposed project focuses on the effects of physical and biological factors on feeding and behaviour of early life stages of great scallop (P. maximus). The factors to be investigated are: food (al gal) abundance, larval stocking density, and light intensity. We hypothesize that these factors significantly influence the growth and survivorship of early life stages of great scallop.