Abundance and population structure of the pearl oyster Pinctada mazatlanica (Hanley, 1856) (Bivalvia: Pteriidae) on the eastern coast of Baja California Sur, Mexico

This study describes the abundance and size structure of the pearl oyster Pinctada mazatlanica (Hanley, 1856) of natural stocks on the eastern coast of South Baja California (28°-23°LN), from 1997 to 1999, at 44 sampling stations. The greatest abundances were registered in the La Paz Bay, Gaviota Beach station (13.89 ± 3.93 ind. 100 m^-2) and at Punta Base. San José Island and Loreto-Montserrat showed lower and similar abundances between stations. Stations Ligüi Bay and El Faro had the greater abundances for the Loreto region. Our results show significant differences in size structure of the pearl oyster between geographical regions. The population of La Paz Bay was characterized by oysters recently established (9.5 to 13.5 mm) and medium size oysters (70 to 80 mm), in comparison with the San José Island and Loreto-Montserrat populations, with oysters from 110 to 150 mm. The pearl oysters with greater height were found on San José Island (102.79<X<174.81 mm confidence limits) and the Espíritu Santo station (98.64<X<167.46 mm confidence limits), respectively. Our results were quite similar to the abundances and structure of the Pinctada mazatlanica populations of Panama coast and of P. margaritifera of the French Polynesia.