粤东外海饵料生物的基本特点与竹筴鱼索饵洄游的关系

THE FEATURES OF FOOD ORGANISMS WITH RELATION TO THE FEEDING MIGRATION OF JACK MACKEREL OFFSHORE EAST GUANGDONG PROVINCE

本文分析了粤东外海鱼类的饵料生物的数量、分布、季节变化,以及它们同高盐水体的关系。并在此基础上,研究了它们对竹筴鱼索饵洄游的影响。粤东外海的饵料生物量的年平均在86—100毫克/米~3之间,一年中一般有两个高峰期,它们分别出现在冬末春初和盛夏。最高生物量达到200毫克/米~3左右;最长持续时间可延续2—3个月。生物量的分布主要受南海表层水和高盐的上层水的影响,高盐水体的消长制约生物量的季节变化和分布。竹筴鱼的索饵鱼群洄游同饵料生物密集区位置移动的方向一致。鱼群逐月移动的方向和途径,大体上是2月份从东径115°30′北纬20°30′向北移动,3月份后折向东北方向,6月份后又折向西南,8月份转向东南(见图6)。

The abundance, distribution, seasonal changes of food organisms and the relationto the high salt water body offshore East Guangdong Province were analysed andinvestigated. On this basis the effect of these factors on the feeding migration of jackmackerel was also studied. The annual average biomass of the food organisms offshoreEast Guangdong Province was about 86--100mg/m^3, and there are two peaks in ayear: one appears at the end of winter and the begining of spring,and the anotheris at mid-summer. The highest biomass reached tO 200mg/m^3, and the longest dura-tion is 2--3 months. The distribution of the biomass is mainly influenced by surfaceand upper layes water of the Nan Hai Sea. The distribution of high salt water. Theand seasonal changes of the biomass are restricted by the variction of the upper layerfeeding migration of jack mackerel shoals,and the shift of high abundance area offood organism coincidently have the same direction. Regarding to the directionand path of monthly shift of the shoal generally, in February it starts from eastlongitude 115°30′ and north latitude 20°3 0′shifting northwards;after March itturns to northeast; after June it turns to southwest and in August it turns tosoutheast.