珠江干流长洲水利枢纽蓄水后珠江鳡鱼(Elopichthys bambusa)早期资源现状

长洲水利枢纽是珠江干流最下游一级的梯级水坝,其正常蓄水后必然改变下游的水文环境特征,也必将对下游的鳡鱼产卵场功能造成一定的影响.为了解长洲水利枢纽蓄水后珠江鱤鱼(Elopichthys bambusa)的资源现状,2008 2013年在珠江肇庆江段设立固定采样点,通过定量弶网对鳡鱼早期补充群体进行调查.结果显示:珠江鳡鱼苗主要出现在4月中旬至8月上旬,多年平均持续时间为97±21 d,盛期在5 7月,鳡鱼苗占鱼苗早期补充群体总量的0.46%±0.21%.鳡鱼苗的出现具有明显的季节变化规律,每年伴随洪峰有3~5次苗汛出现,苗汛次数与洪峰次数之间存在显著相关关系,但苗汛峰值大小与径流量之间不存在显著相关关系.鳡鱼苗多年平均资源量为16.89×108±9.16×108尾,繁殖群体总量约为52.8 t.研究表明:长洲水利枢纽蓄水后鳡鱼早期资源量呈下降趋势,但珠江禁渔缓解了长洲水利枢纽建设对珠江鳡鱼资源的影响.基于以上结果,为长洲水利枢纽蓄水后珠江鳡鱼的保护提出了建议.

Status of Elopichthys bambusa recruitment stock after the impoundment of Changzhou Hydro-junction in Pearl River

Changzhou Hydro-junction was the most downstream dam in the main stream of Pearl River. Its impoundment would change the characteristics of the hydrological environment of the downstream, and may effect the function of Elopichthys bambusa spawning grounds. In order to understand the influence, E. bambusa recruitment stocks were surveyed by quantify drifting net at Zhaoqing after the impoundment of Changzhou Hydro-junction in the Pearl River from 2008 to 2013. The results showed that E. bambusa larvae usually occurred from mid-April to early August, and peaked from May to July. The annual mean duration was 97±21 days. E. bambusa recruitment stock was accounted for 0.46%±0.21% in the total larvae fishes. The occurrence of E. bambusa larvae showed obviously seasonal patterns. There were 3-5 times of the peaks every year following the flood, and there was significant correlation between the peak times of larvae fish and the flood. E. bambusa recruitment stock was about 1.689±0.916 billion, and the breeding population was estimated about 52.8 t. The result indicates that the E. bambusa larvae population had decreased after Changzhou dam operation, but prohibition of fishing in the Pearl River has slowed down the decaying. Suggestions for fish protection after the impoundment of Changzhou Hydro-junction are given.