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 l(-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 l h(-1) cm(-1)) at 20.7 degreesC. Most feeding experiments were carried out at 10 to 13 degreesC, 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.