长江口水域主要渔业生物资源状况的分析

利用长江口水域20世纪90年代的拖网生产资料以及生物学测定数据,分析该水域拖网生产的渔获种类及优势种的资源变化状况。结果表明:20世纪90年代各时期长江口水域拖网生产的渔获物中,鱼类占92%以上,头足类和甲壳类所占的百分比较小,分别在8%和1%以下。每个时期的拖网生产的种类数基本相当,都为40种左右;同一时期的不同季节和各季节的不同时期间的种类数均有明显的变化。随着时间的推移,长江口水域拖网渔获物优势种类的组成发生了一定的变化。从90年代初期到末期,大部分传统优势种的渔获比例相对稳定,某些优势种的渔获比例有较大的波动或急剧减少,小型低质鱼种的渔获比例和种数增加。对带鱼、小黄鱼的体长组成结构分析表明它们的群体从20世纪80年代开始趋于明显的小型化,当前的小型化程度已经相当严重;而在此期间黄鲫的体长组成结构变化不大。该水域的优势种类组成和主要优势种类体长组成结构的变化是和逐渐增加的捕捞力量以及水域环境变化相关联的。

Dynamic analysis of fishery biology resources of trawl in waters of the Yangtze River Estuary

The paper analyzed variety status of fishery species and dominant species in trawl production based on data of trawl production and biology measuration in waters of the Yangtze River Estuary in 1990's. The result indicated percentage of Fishes was beyond 92%, Cephalopods and Crustaceans' percentage were very little, under 8% and 1% respectively, in trawl production of waters of the Yangtze River Estuary in 1990's. The number of species was always about 40 in each period. There were obvious changes in the number of species in different seasons of the same period and different periods of the same season. As the time passed, there were some changes of dominant species composition in trawl catches of waters of the Yangtze River Estuary. From early to late, most traditional dominant species were comparatively stable. However, there was a great fluctuation or sharply decrease in percentage of catch for some traditional dominant species, and small and low-quality fishes increased in percentage of catching and number of species. Analysis of body length structure of Trichiurus japonicus and Larimichthys polyactis revealed that there obviously had been a trend of miniaturization of stock since 1980's, the current miniaturization is very serious, but there was little change in body length structure of Setipinna taty. The varieties of composition and body length structure of dominant species were correlative with the gradual increased catching effort and change of environment of the water area.