Functional descriptions of feeding and energetics of the Pacific oyster Crassostrea gigas in New Zealand

Abstract

Pacific oysters Crassostrea gigas were fed a mixed diet of algae and silt over a range of concentrations from 0.8 to 637 mg 1-1, and an organic content ranging from 0.7 to 72 %. These data were used to parameterise a set of functions describing the physiological response of oysters to varying environmental conditions. All parameters were standardised to body length. There was greater variation of size-specific clearance rate (CR) standardised to dry tissue weight than to length. CR increased hyperbolically with temperature with a maximum rate (0.24 1 h-1cm-1) at 20.7°C. Most feeding experiments were carried out at 10 to 13°C, except for the measurements of temperature effect. CR increased rapidly with increasing seston concentration, peaked at about 10 mg l-1, above which it consistently decreased. It was modelled as a function of pumping rate of water and extraction efficiency of particles from water. The filtration rate was found to be a Type 2 hyperbolic function of seston concentration within the range tested. Ingestion rate was described as a function of food quantity, quality and selective ingestion of organic particles. A positive effect of organic content on absorption efficiency was found only at a very low organic content of less than 5 %, while above this level, absorption efficiency was constant at 86 %. Oxygen consumption rate had an allometric relationship to body size and increased over the range of experimental temperatures.