葛洲坝产卵场中华鲟繁殖群体数量与繁殖规模估算及其变动趋势分析

Estimation on the Spawning Population and Spawning Sizes of Chinese sturgeon(Acipenser sinensis)and Trend Analysis of Their Change in Recent Years

采用声学探测的方法,进行中华鲟(Acipenser sinensis)繁殖群体数量的估算。2005～2007年,第1次产卵前的资源量分别为235尾、217尾和203尾;第1次产卵后的资源量分别为157尾、157尾和102尾。采用食卵鱼解剖统计和股分析的方法对中华鲟的自然繁殖规模进行估算,其结果为,2005～2007年间中华鲟的产卵量分别为356万粒、119.6万粒和238.6万粒。结合历史相关研究数据,对近10年的中华鲟繁殖群体数量和繁殖规模的变动趋势进行分析,结果显示,在20世纪90年代中期,第1次产卵前的中华鲟繁殖群体数量下降趋势明显,但2002年以来其数量趋于基本稳定,年际间的差异没有统计学意义(P>0.05)。自2002年以来,第1次产卵后停留产卵场的中华鲟数量有增加的趋势,而中华鲟的繁殖规模近10年来呈现极其显著性的下降趋势(P<0.01)。

Chinese sturgeon （Acipenser sinensis ）was once widely dispersed in almost all watersheds draining towards the western coasts of the Pacific Ocean. Today, the species is one of the highly endangered fish species in China and can be found only in the Yangtze and Pearl rivers and their adjacent coastal and marine areas. Due to the construction of the Gezhouba Dam, spawning grounds for the fish were drastically restricted but fortunately remained in the Yangtze River at a small-scale site located just downstream along a short reach of the river closely to the dam. In this paper, the author used fisheries-acoustics method to detect the mature Chinese sturgeon individuals and estimate the spawning stocks. And applying Jones＇s Length-based cohort analysis to eatimates the annual abundance of C. heterodon with fishing data collected in autumns. Then according to the quantitative ratios of them to C. heterodon in catches, abundance of the rest egg-predatory fishes were counted. In the end, we can estimate the Chinese sturgeon＇s spawning size by such data. The results show that, From 2005 to 2007, the spawning stock of Chinese sturgeon is 257ind. , 237ind. and 203ind. respectively, No significant difference in annual amounts was observed in the spawning ground among those years. There are amount of sturgeon stay on the spawning ground after spawning seasons, with the number increasing in last 3 years. The length - based cohort analysis show that, the estimated Chinese sturgeon laying are 3 560 000 grains,1 196 000 grains and 238 6000 grains respectively in the last 3 years, Compared with historic data, the reproduction size decrease sharply in recent years, The drop tendency is extremely remarkable （P 〈0.01 ）. Chinese sturgeon had migrated to the spawning grond , but as the entironment had changed greatly in recent years, many of them can＇t spawn.