ABSTRACT
The migration and settlement of oyster larvae significantly affect the distribution, recruitment, establishment and ecological services of oyster populations. We investigated the variations of Crassostrea sikamea larvae abundances between the two water layers and between the two experimental sites (seed bed and spawning bed) in Xiangshan Bay within a tidal cycle (9 sampling times), and explored the spatial patterns in larval settlement and spat growth at three intertidal zones (top, T; middle, M and bottom, B) of both experimental sites by a field settlement experiment. At the seed bed and spawning bed, oyster larvae abundance at the surface water significantly changed with sampling time. At the seed bed, oyster larvae abundance (20.8±5.6 larvae·L-1) was greatest at the high flood tide, and was significantly greater than that at the other eight sampling times. Contrasting results were found at the spawning bed where oyster larvae abundance was the lowest (0.1±0.1 larvae·L-1) at the high flood tide. At each site, oyster larvae abundance at the bottom water did not change within the tidal cycle. At the seed bed, total abundance, survival rate and shell height of the settled oysters significantly varied across intertidal zones, ranking as B>T=M for total oyster abundance, and T>M>B for survival rate and shell height. There was no significant difference in live spat abundance among intertidal zones. At the spawning bed, the total and live abundances, survival rate and shell height of the settled oysters had no difference among intertidal zones. Our results indicate that oyster larvae commonly settle at the high flood tide, and the abundance of settled spats are similar between seed bed and spawning bed.
