Settlement and early growth of the scallop Argopecten circularis in Bahia Concepcion, Baja California Sur, Mexico

Research on scallop population in Bahia Concepcion has as its objectives: 1) to determine the intensity and duration of spatfall on artificial collectors, 2) determine a means to keep the spat enclosed for 4 months until they are ready for release and repopulation. During the 7 years of this study, the major scallop spatfall was observed to occur during January to March, Spatfall one year can therefore be related to recruitment in the next with years of high and low spatfall reflected in subsequent differences in recruitment. For Bahia Concepcion in 1987, the settlement resulting from a reduced winter-spring spawning was 500 spat per bag. The total stock was estimated to be 70 million scallops. For 1988, the settlement increased to 40,000 spat/bag and the stock was estimated at 120 million scallops. For 1991, the settlement decreased to 18,000 spat/bag and the stock was about 50 million scallops. For 1994, the settlement was very low, with only about 157 spat/bag, and the stock decreased to 1 million scallops. Weekly data for 1994, showed variation between 25.3 to 358.7 spat/bag. The final size of the scallops held for 4 months in an enclosure will be 4.5 to 5.2 mm when released. (DBO)