东山岛近岸水域厦门文昌鱼浮游幼体的分布

通过1990年5、8、11月和1991年1月的调查发现，东山岛近岸的厦门文昌鱼（Branchiostomabelcheri）浮游幼体，主要分布在该岛的东部和南部水域。其数量相当多，基本上集中出现在春末（5月）和夏季（8月），平均密度分别为24．4尾／m3（或402．73尾／m2）和232．2尾／m3（2．394×103尾／m2），最大密度（8月下旬）达888尾／m3（1．332×104尾／m2）。体长组成表明，该水域的厦门文昌鱼为分批产卵繁殖。幼体生长发育到体长5mm左右时，身体的形态结构与成体基本相同，并开始陆续转为潜沙生活。

Distribution of planktonic larvae of Branchiostoma belcheri at nearshore waters of Dongshan Island in Fujian

based on the investigation results in May, August, November 1990 and January 1991,the planktonic larvae of lancelet Branchiostoma belcheri found to be mainly distribution innearsllore waters of east and south Dongshan Island. Its quantity was considerablyabundant. The planktonic larvae occur mainly in late spring (May) and summer (August ).Average density is 24. 4 ind. /m3 (or 402. 73 ind. /m2) and 232. 2 ind. /m3 (or 2 393, 64 ind. /m2 )respectively. The greatest density occurs in late August (888ind. /m3 or 13 32o ind. /m2 ).Their body length composition shows that Branchiostoma belcheri spawns group by group.When the larvae reach about 5. 0mm in body length, their structure is basically the same tothe adult and they begin benthic life in succession.