象山港熊本牡蛎幼体分布、附着及生长的空间格局

牡蛎幼体迁移与附着影响着牡蛎的空间分布、资源补充、种群维持及生态服务功能。本研究通过野外调查,监测了1个完整潮汐周期(9个潮时采样)内象山港2个试验点(采苗场和产卵场)表层、底层水体中熊本牡蛎幼体的时空动态,并开展野外附着试验,检验了熊本牡蛎在2个试验点和3个潮区(上层T、中层M和底层B)附着及生长的空间格局。结果表明: 在1个完整潮汐周期内,2个试验点表层水体中牡蛎幼体丰度均有显著的时间变化,采苗场表层水体中熊本牡蛎幼体丰度最大值(20.8±5.6 ind·L^-1)出现于高平潮时,显著高于其他8个潮时;而产卵场相反,高平潮时牡蛎幼体丰度最低(0.1±0.1 ind·L^-1);2个试验点底层水体中牡蛎幼体丰度在不同潮时之间均无显著差异。采苗场附着牡蛎总丰度、成活率和壳高在不同潮区间差异显著,牡蛎总丰度大小顺序为B>T=M,成活率和壳高的大小顺序为T>M>B,活体牡蛎丰度在潮区之间无显著差异。产卵场附着牡蛎总丰度、成活率、活体牡蛎丰度和壳高在不同潮区之间均无显著差异。表明高平潮时是熊本牡蛎附着的主要时段,产卵场和采苗场具有相似的牡蛎稚贝附着密度。

Spatial pattern in larval distribution,settlement and growth of Crassostrea sikamea in Xiangshan Bay,Zhejiang Province,China

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.