Feeding and growth of the Japanese oyster Crassostrea gigas is simulated by a deterministic model. However, physiological processes, estimated by statistical relationships, have not been tested under extreme environmental conditions such as high level of suspended particulate matter. Ecophysiological experiments were therefore conducted in situ in the Bay of Marennes-Oléron during a spring and neap tide cycle in May 1991, to get a better representation of 2 important components of the energy budget of the Japanese oyster: clearance rate and selection efficiency. The relationships previously established by Raillard et al. (1993) are re-evaluated by integrating the action of high seston load, typical of tidal effect within estuaries, on the physiological processes. For the clearance rate, the re-evaluated parameterization includes: - a negative effect of turbidity. - a clogging threshold set to 192 mg/l. Selection efficiency parameterizations are modified by incorporating : - a constant inorganic ingestion for increasing seston load, set to 17 % of the inorganic filtered ration. - an upper selection threshold for the particulate organic matter caused by an overload of particulate material. This threshold was set to 160 mg/l. The oyster growth model should be enhanced by integrating theses new equations built-up on realistic field conditions, where food availability is regulated by tidal variation.