Knowledge of the gametogenic cycle and biochemical composition of commercially valuable species is important in aquaculture. Monthly variations in meat yield, gonadal development and biochemical composition of the bivalve Tapes decussatus were studied from January 2002 to December 2002 in the Sufa Lagoon in relation to environmental conditions. Histological evidence showed that gametogenesis began in January and major spawning started in July and appeared to continue into August and September. The majority of individuals were resorbing their gonad, or alternatively in a period of gonadal inactivity in October, November and December. When the gonad stage was ripe in April, the glycogen value was at the maximum level in contrast to protein which was at the minimum value. The glycogen value was at the minimal level during spawning and resting period. During the late gametogenesis the protein value was the highest in March and the following month when the gonad was ripe, protein was at the lowest. Lipid content fluctuated throughout the study. During the gametogenesis, the meat yield was observed to range between 12.7% and 26.8%. The results of this study showed that six stages of gonadal development of T decussatus were observed in transplanted area. Seawater temperature was the major factor rather than food availability on gametogenesis of carpet shell clam in the study area. (C) 2009 Elsevier B.V. All rights reserved.