Spat of 2 pectinid species of commercial interest were grown in suspension to study the growth of the gonad, digestive gland, and adductor muscle at 3 different depths (2.5 m, 7.5 m, and 12.5 m). For the experiments, we used spat immediately after they were detached from the collectors (Aequipecten opercularis) or 3–4 mo later (Chlamys varia). The first sexual maturation of each species was recorded. The variations observed in the gonad development pattern were clearly a result of the effect of depth on the gonad growth of the 2 species. Both species showed faster gonad development at 2.5 m. Reproduction of C. varia was more intense in deeper water. This was also the case for A. opercularis in the first reproduction period, from the end of winter to early summer. After a resting period in summer, there was a first peak of gonad growth at 2.5 m in October that did not occur at 7.5 m and 12.5 m. There was a peak in January at all depths. The reserve storage organs of both A. opercularis and C. varia showed a regular pattern of evolution. In general, the variations in the reserve organs followed the same pattern at all depths with 2 exceptions: the digestive gland in C. varia in spring at 2.5 m, which showed a faster growth rate related to higher temperatures; and the digestive gland and muscle in A. opercularis, which showed a large growth peak in late spring and early summer at 12.5 m that did not occur at other depths and that was related to lower temperatures and greater food availability. The growth of the reserve organs was more conservative despite the variations in the environmental conditions that occurred during the experimental period. Gonad growth was affected more by environmental changes, and was more versatile.