基于水声学方法的天目湖鱼类季节和昼夜空间分布研究

采用水声学方法系统地对天目湖春夏秋冬四季鱼类水平和垂直空间分布进行了调查研究,同时对昼夜探测的差异性进行了比较,并对不同季节间鱼类聚群形态进行了探讨。研究结果表明,天目湖鱼类在不同季节间存在规律性水平迁移,从全湖角度分析,天目湖鱼类资源昼夜间的水平空间分布无明显差异特征,但在春末和夏季的局部区域里,昼夜间鱼类存在一定近岸—远岸的水平迁移;不同季节和昼夜间,鱼类垂直分布差异明显,且在存在温跃层的夏季7月昼间,鱼类密度垂直分布与水温的垂直分布关系密切,温跃层以下的鱼类密度基本为0;天目湖鱼类在四个季节都属于成群分布类型,但季节间鱼类聚群形态不同,在冬季的1月呈现出典型的聚集,相对于昼间,春夏季鱼类在夜间分布更为均匀、分散,且水平探测表明在夜间水体表层存在大量鱼类分布。

Seasonal and daily spatial distribution of fish in Lake Tianmu based on the hydroacoustic method

The seasonal and diurnal changes of horizontal and vertical spatial distribution of fish were studied by applying the hydroacoustic method in Lake Tianmu. The results showed that there was regular horizontal migration of fish between different seasons and no significant difference in horizontal distribution between day and night in Lake Tianmu. However, there existed a slight diurnal change in the inshore-offshore horizontal migration in some parts of the lake area during the late spring and in the summer. Significant differences in vertical distribution were found between seasons and between day and night. The vertical distribution of fish density was significantly affected by the water temperature stratification in July when there was a thermocline, and the fish density in hypoliminion was almost zero. The fish in Lake Tianmu was distributed in groups in the four seasons, but the typical cluster form occurred only in January. Relative to the daytime, the fish distribution at night was more uniform and scattered. Moreover, horizontal survey showed that a large number of fish was spread in the upper water layer at night.