Growth and survival of the scallop Lyropecten (=Nodipecten ) nodosus (L. 1758) in suspended culture in the Cariaco Gulf (Venezuela) during a non-upwelling period

Abstract

Growth and survival of the scallop Lyropecten nodosus were studied in 1997 at two sites (inner and outer Turpialito Bay) during a non-upwelling period normally occurring between August and November. Individuals had an initial shell height of 4.86 cm (SD=1.64 cm). Both experimental groups were held in suspended plastic baskets at the same depth (4 m). Measurements of shell height and dry weights of shell, gonad, digestive gland, remaining tissues and shell biofouling were taken at monthly intervals. Environmental parameters, including temperature, phytoplanktonic biomass, total particulate material (TPM) and associated organic (POM) and inorganic (PIM) fractions, were recorded simultaneously. At the end of the study, significant differences in growth and survival of scallops were observed between the two experimental sites. Scallops maintained inside the bay showed a 22% greater increase in shell height (7.41 ± 0.27 cm) than those placed outside the bay (6.37 ± 0.41 cm). Survival of scallops inside the bay was 31% higher compared with scallops outside. The greater availability of food of phytoplanktonic origin during the first two experimental months (July and August) together with greater POM throughout the whole experimental period except September, at the inner bay site, probably explained survival and growth differences observed between the two locations. Results suggest that, during the non-upwelling period (characterized by low primary productivity and high water temperatures), POM of sedimentary origin may play an important role as an energy source required for metabolic and reproductive activities of L. nodosus.