Growth, survival and environmental effects on three cohorts of the pearl oyster Pinctada imbricata, under suspended culture

Abstract

The growth and survival of individuals of the pearl oyster Pinctada imbricata (spats of 16-24mm antero-posterior shell length ) belonging to three different cohorts ( CI, CII and CIII ) were evaluated during three contrasting environmental periods . The cultures were made in Japanese baskets suspended from a long line , in Turpialito site , Gulf of Cariaco , Venezuela. Cohort CI was cultured from October 2007 to April 2008 (covering the period of stratification and upwelling waters of the area) , the CII from June 2008 to February 2009 (dominated by the stratification period and the start of the coastal upwelling ) and the CIII from February 2009 to July 2009 (coastal upwelling period ). Monthly determinations included survival , the length and mass of the shell , the mass of muscle and other tissues , as well as the fouling mass on the shells and the number of gastropods of the genus Cymatium spp. recruited in the culture baskets . The variation of water salinity , temperature, chlorophyll a , seston and dissolved oxygen were determined biweekly. Survival was inversely associated with the incidence of Cymatium spp . The temperature and food availability were associated to growth. The highest rates of growth and survival were observed in individuals of CIII , thus it is suggested that the upwelling period is the most suitable for the cultivation of the species .