山东半岛南部产卵场温跃层对鳀鱼鱼卵垂直分布的作用

Function of thermocline for vertical distribution of anchovy eggs in the spawning ground of the southern waters to Shandong Peninsula

2000～2004年5～7月"北斗"号生物资源调查船对山东半岛南部产卵场进行多学科综合调查期间,于2003年6月17～18日和6月27～30日分别在35°01.9′N、120°32.9′E海区和35°03.3′N、120°26.4′E海区进行了25h和64h的水团追踪观测调查,鳀鱼鱼卵的数量、垂直分布与水温的分布为重点调查内容。调查结果表明:水温垂直分布的变化、海水混合的强弱、水体的辐聚/辐散等物理过程对水体中鳀鱼鱼卵数量和鳀鱼鱼卵在不同水层的分布有很大影响。温跃层分布深度的波动引起水体的垂直交换(混合)、水平对流(辐聚/辐散)和跨跃层的物质交换。温跃层深度变浅时,上混合层水体的厚度变薄,跨跃层的向上混合,将下混合层水体中和温跃层中的鳀鱼鱼卵输运到温跃层和上混合层中,同时表层水体发生辐散现象,使得下混合层、温跃层和上混合层水体中鳀鱼鱼卵数量减少、密度减小,导致整个水柱内鳀鱼鱼卵的数量减少;温跃层深度加深时,上混合层水体的厚度增加,跨跃层的向下混合,将上混合层水体中和温跃层中的鳀鱼鱼卵输运到温跃层和下混合层水体中,同时表层水体发生辐聚现象,使得上混合层、温跃层和下混合层水体中的鳀鱼鱼卵数量增多、密度增大,导致整个水柱内鳀鱼鱼卵的数量增多;温跃层水体中鱼卵数量和密度的变化较上混合层和下混合层水体更为显著。水体中温跃层的存在、温跃层分布深度的波动及其波动的程度对上混合层和温跃层中鳀鱼鱼卵的数量和密度的变化起着主导作用,导致鳀鱼鱼卵数量垂直分布的剧烈变化。

The multidiscipline integrated investigations on the spawning ground of the southern waters to the Shandong Peninsula were carried out from May to July during 20002004 by R/V Beidou. Two drift experiments were deployed at 35°01.9＇N、120°32.9＇E for 25 hours from 17 to 18 and at 35°03.3＇N、120°26.4＇E for 64 hours from 27 to 30,June of 2003. The main goal of this survey is to get the amount of anchovy eggs,the eggs＇ vertical distribution and the water temperature profile. It is shown that the variation of water temperature profile,the water mixing intensity and the convergence/divergence processes could have significant influences to the amount of anchovy eggs and their distribution in the water column. The variation of the depth of thermocline could induce the water vertical exchange,horizontal advection（convergence/divergence） and the mass exchange across the thermocline. When the thermocline became shallower,the upper mixing layer turned to thinner. The upward entrainments across the thermocline could mix the eggs of the lower layer into the thermocline and the upper mixing layer respectively. At the same time,the surface water divergence made the amount and density of anchovy eggs in the lower mixing layer,the thermocline and the upper mixing layer decrease which cause the amount of eggs less in the whole water column. On the opposite,when thermocline deepening the upper mixing layer became thicker. The downward entrainment could transport the eggs of the upper layer into the thermocline and the lower mixing layer respectively. Meanwhile the surface water convergence caused the increasing of the amount and density of anchovy eggs in the three layers and the whole water column. The amount and density of eggs in the thermocline varied much larger than that of the two mixing layers. The existence of the thermocline,the variation and its extent of the thermocline depth could dominate the variation of the amount and density of eggs. These may cause the huge change of the eggs＇ vertical distribution.