Spat collection studies on pearl oysters Pinctada mazatlanica and Pteria sterna (Bivalvia,Pteriidae) in Bahia de La Paz,South Baja California,Mexico

The present work deals with the temporal and bathymetrical variations of the epifaunal community associated with two species of pearl oysters (Pinctada mazatlanica and Pteria sterna) during a seed collecting season from June to November 1989. A total of 63 items (species, genera and/or families) were recorded; their variations in presence and abundance were followed during three periods (June–July, August–September and October–November). The collectors were examined for different immersion times (2, 4, 6 and 8 weeks) for each period. Community structure was compared through the Brillouin Index, the Morisita Index and the Importance Value.We define the chronology of spatfall for both species of pearl oysters and their bathymetrical distribution. Relationships between these species and the epifaunal community present into the collectors were analysed, searching for possible noxious effects on the survival of juvenile pearl oysters, and identifying index species related with their spatfall. A strategy for starting massive seed collection of both species is established, particularly for P. mazatlanica.