秦山核电温排水对鱼类分布的影响

根据2010年5月(春季)、2010年9月(夏季)和2009年12月(冬季)秦山核电海域渔业资源调查资料以及秦山核电站温排水扩散数学模拟结果,通过秦山核电温排水海域鱼类季节密度的时空分布、优势种、优势种对鱼类总数量的贡献,探讨并分析了秦山核电海域温排水对鱼类分布的影响。结果显示,春季、夏季和冬季的尾数密度分别为5.55×10~3 ind/km~2、22.10×10~3 ind/km~2和10.52×10~3 ind/km~2,重量密度分别为33.80 kg/km~2、59.06 kg/km~2和66.46 kg/km~2。秦山核电海域渔业资源数量季节变化的规律与其他海域相反,冬季最高,春夏季较低,主要与冬季温排水海域具有暖池效应,形成部分鱼类滞留在此越冬有关。温排水平面分布对鱼类分布有重要的影响。主要表现在夏季温排水区域鱼类密度低于其他水域,冬季相反,鱼群滞留在温排水热羽区域,因而显示出温排水海域有较高的鱼群密度。温排水对不同适温习性鱼类影响不同,暖温种能够适应一定的低温,例如,刀鲚(Coilia ectenes)可以在温排水水域越冬,而对高温有耐受性的棘头梅童鱼(Collichthys lucidus)夏季在温排水水域成为优势种。鱼类优势种的适温性决定着鱼群的分布特征,冬季最重要的优势种为刀鲚,在尾数上的贡献率高达45.02,由于该种在温排水的热羽区域分布密集,形成温排水水域鱼群密度大于周边水域的现象。由于温排水改变了渔场环境,导致新的越冬场的形成,有可能形成新的渔汛,引起当地渔场属性的改变。

Effects of the thermal discharge from Qinshan Nuclear Plant on the distribution pattern of fish

Based on the data taken from fishery resource surveying of the sea areas around Qinshan Nuclear Plant dur-ing spring (2010-05), summer (2010-09) and winter (2009-12) and the mathematical simulation results of thermal dis-charge diffusion in Qinshan Nuclear Plant, we studied the temporal and spatial distribution pattern of fish assemblies, the dominant species, and the contributions of dominant species to fish quantities in the water of Qinshan Nuclear Plant. The results showed that the density of fish in terms of individuals was highest in summer (22.10×103ind/km2), interme-diate in winter (10.52×103ind/km2) and lowest in spring (5.55×103ind/km2). However, the seasonal variation in fish quantities in terms of weight was different from other waters. The fish density in terms of weight was highest in winter (66.46 kg/km2), intermediate in summer (59.06 kg/km2), and lowest in spring (33.80 kg/km2).The seasonal variation in fish resource quantities was different to other seas; the densities in terms of weight were higher in winter than those in spring and summer. This was probably related to thermal discharge from the plant making the proximal sea regions warmer than the surrounding sea waters, which could benefit the fish assemblies in winter because of a warm pool ef-fect. Thus, fish assemblies aggregated in the thermal plume of the plant to overwinter. Horizontal distribution of ther-mal discharge has an important effect on fish distribution patterns. The fish density in the thermal discharge seas in summer was generally lower than other seas and was the opposite in winter: fish may have been stranded in the hot thermal discharge plume areas, thus showing a higher fish density. Thermal discharge has different effects on fishes with different adaptabilities to temperature; the warm temperature species that are adapted to relatively low temperature, such asCoilia ectenes, can overwinter in the thermal discharge seas, whileCollichthys lucidus, which has high thermal tolerance, became the dominant species in the thermal discharge-impacted seas in summer. The adaptability to tem-perature of the dominant species of fish determines the distribution characteristics of fishes; the most important domi-nant species in winter wasCoilia ectenes, whose contribution rate on the mantissa was up to 45.02. They aggregated densely in the hot thermal discharge plume area, which caused the fish density in the thermal discharge seas to be greater than the surrounding waters. The thermal discharge-inducedchange in the fishes’ environment led to the forma-tion of new wintering grounds, which would be likely to form a new fishing season, leading to changes in local fishery attributes.