Abstract: The relationship of respiration and excretion to body size in Crassostrea hongkongensiswas studied under controlled laboratory conditions, in hopes of providing some scientific data for assessing the carrying capacity of aquaculture, ecological and physiological studies of C. hongkongensis. The results showed that the oxygen consumption rate (R_O) decreased significantly over the increase of dry tissue weight (W) among the groups of different body sizes (P<0.01), and the ammonia excretion rate (R_N), and phosphorus excretion rate (R_P) of C.hongkongensisyielded significant variations among the groups of different sizes in terms of dry tissue weight (P<0.01). However, no significant difference of O/N and N/P ratio among these groups was detected (P>0.05). The oxygen consumption rate, ammonia excretion rate, and phosphorus excretion rate of C.hongkongensiswere correlated negatively with the dry tissue weight. The correlations were presented by the equations R_O=1.8232W^-0.7600 (R²=0.8313, P<0.01); R_N = 0.0930W^-0.6582 (R² = 0.7444, P<0.01); and R_P = 0.0126W^-0.8874 (R² = 0.9224, P<0.01). The values of O/N were high in all groups, and the N/P ratios showed incremental trend over the dry tissue weight increasing among the groups.

Key words: Crassostrea hongkongensis, respiration, excretion, body size