虾池纳潮期日本刺沙蚕幼虫数量及其沉降的研究

于1992年2月27日－5月30日在文登市高岛盐场养虾场，对日本刺沙蚕（卵、各期胚胎和幼虫）的纳潮数量和幼虫的沉降进行现场调查和实验研究。结果表明，对养虾生产有意义的纳潮期有3个。3月上旬的新月潮，持续12d，数量为（25－50）×103个／m3，主要组成是受精卵、各期胚胎和担轮幼虫。3月甲旬的满月潮持续7d，数量为（2－5）×103个／m3。4月上旬的新月潮持续8d，数量为（2－3．5）×103个／m3。纳潮量与潮汐关系密切，但与平均潮高无显著的相关。各潮期的纳潮数量比应是4：4：2。对16个纳潮虾池测试的平均沉降量为4492个／m2。据现场调查和实验研究，日本刺沙蚕幼虫的沉降期可划为暂时沉降（5－6刚节）和变态沉降（7—10刚节）。出现暂时沉降（4月15日以后），便可执行纳潮后的排水等虾池早期管理。纳潮的定量监测方法简单、快速和准确，可用来指导虾池的纳潮。

A STUDY ON NEANTHES JAPONICA (IZUKA) LARVAL DEVELOPMENT, DENSITY, AND SETTLEMENT DURING THE SEASON OF BRING TIDAL

A quantitative study using tidal flow to bring eggs, embryos and larvae into the shrimp ponds at five inlet stations from Wuleidao Bay in the Yellow Sea from Feb. to May in 1992 showed that three tidal periods are very important for prawn acquacuture. The first period lasting twelve days is at about the new moon in early March, with larval density (25 - 30) ×10³ ind/m³. The main developmental stages include fertilized eggs, embryos at different stages and the trochophora. The second period(7 days) is just before and after the full moon in mid-March, with numbers of (2 - 5) ×10³ ind/m³. The dominant stage is the three-setiger nectochaete. The third period (8 days) is just before and after the new moon in early April, with density of (2 - 3.5) ×10³ ind/m³. The four-setiger and five-setiger nectochaetes are domi-nant stages. On the basis of the results of the present investigation, it is suggested that the proportion of each tidal flux to bring into the ponds in three tidal periods should be 4,4, and 2 respectively.

The correlation between the density and the mean tidal flood level is not significant, although the former shows close relationship with occurence of tidal flood. The mean density of settled larvae was 4 492 ind/m², based on the examination of sixteen selected prawn ponds. Based on the determination in situ and experimental observation, settlement of Neanthes japonica larvae can be divided into a temporatory settled stage from five-setiger to six-setiger nectochaete and the metamorphosis settled stage from seven-setiger nectochaete to ten-setiger juveniles. As the temporary settled stage occurs(from the mid-April onwards) the early management of shrimp ponds can be started.

The quantitative method of monitoring the eggs, embryos and larvae of Nereids, because of its simplicity, rapidity and accuracy, is applicable to prawn culture during its spawning seasons.