Monitoring of sea scallops Placopecten magellanicus in bottom seeding trials using video in Miquelon bay, Saint Pierre et Miquelon, France

Placopecten magellanicus production in Saint Pierre et Miquelon (NW North Atlantic) has been developed through direct seeding of juveniles on leased areas. However, most of the culture occurs in deep water ranging from 30 to 70 meters, which requires a monitoring by video to facilitate the grow-out and survival evaluation. In August 2008, a submersible leaded structure was connected by a video cable to the surface and observation screen was defined through the video, an altimeter and two lasers. The pictures were recorded on board on hard drive and digital video recorder DVCAM, and data were georeferenced by VIDEONAV software. Analysing the video tapes allows to establish a thematic database on the ground structure, presence or absence of seeded and wild scallops or predators as well as the mortality rate. Those data could also be interpolated with Geographic Information Systems (GIS) like Arc View or Adelie softwares. reliminary results showed that 70% of scallops observed were located in seeding beds. Growth rate has also been estimated through the use of laser beams on the bottom, estimate by the altitude from the camera and it was measured that length increased between 2cm and 2.5cm per year in P. magellanicus.. However, only one campaign was carried out in 2008, and further monitoring are needed to provide advice on the management of the growing areas, such as the relationship between depth and scallop growth rates and dispersion and mortality rate assessment, specially through predation