三峡水库正常运行期间四大家鱼的时空分布特征

调查三峡水库正常运行期(2011-2015年)库区干流5个江段(秭归、巫山、云阳、涪陵、江津)的鱼类资源,对库区干流四大家鱼的时空分布特征进行研究,并探讨三峡库区四大家鱼受上游水电开发以及库区其他因素影响的情况,旨在为三峡库区四大家鱼保护措施的提出提供基础数据支撑。研究结果表明:四大家鱼在渔获物中的数量百分比从2011年的3.52%下降到2015年的1.86%,而重量百分比则先从2011年的13.47%迅速上升到2012年的28.06%,然后波动下降到2015年的24.30%,其中鲢、鳙、草鱼均在数量百分比上呈现波动下降趋势,而在重量百分比上则均呈现先上升后下降的趋势;5年间,四大家鱼的主要分布区域逐渐从涪陵至秭归江段转移到云阳和秭归江段,其中鲢、鳙、草鱼的主要分布区域均从云阳至秭归江段转移到云阳和秭归江段。三峡库区四大家鱼群体面临的主要问题是金沙江梯级水电站运行对其产卵活动的影响以及库区普遍的过度捕捞。

Temporal and Spatial Distribution of the Four Major Chinese Carps in Three Gorges Reservoir during the Normal Operating Periodoperation period and the problems faced by these four carps

Many studies have shown that construction of Three Gorges Reservoir (TGR) effected community structure and distribution of economic fish species. The current status and spatial-temporal distribution of the four major Chinese carp species in TGR are not known. Xiangjiaba and Luoxidu Hydropower stations in the lower Jinsha River began operations in 2012 and 2013, and these are also significantly effecting the hydrologic regime of TGR. A fishery resource investigation was conducted in five sections (Zigui, Wushan, Yunyang, Fuling, and Jiangjin) of TGR during the normal operation periods from 2011 to 2015. Based on the data gathered, the spatial-temporal distribution of the FMCCS in the main stem of TGR was characterized. The ecological problems faced by the FMCCS resulting from the cascaded hydropower stations on the Jinsha River were assessed to provide support for FMCCS protection. The Zigui and Wushan sections are located in the lower reach of TGR, the Yunyang in the middle reach, and Fuling and Jiangjin in the upper reach. The fishery investigation was conducted twice in May-July (low water level period) and October-December (high water level period) with four-six catches each day for 14-20 days each year. Fish were collected by gill net and shrimp pot; each specimen was identified and total length, body length and body weight were measured. Over the 5-year period, a total of 2005 FMCCS individuals (754.05 kg) were collected from the five sections, with dominance by silver carp (1 270 individuals, 63.35%) and black carp the fewest in number (22, 1.09%). The number of FMCCS, relative to total number of fish collected, decreased from 3.52% in 2011 to 1.86% in 2015, while the weight percentage increased from 13.47% in 2011 to 28.06% in 2012, and then decreased to 24.30% in 2015. The number percentages of silver carp, bighead carp and grass carp all declined, whereas the weight percentage fluctuated, increasing and then decreasing. The ranges in average length of silver carp, bighead carp, grass carp and black carp were, respectively, 193-308 mm, 166-265, 129-493 mm and 95-282 mm, and the average weight ranges were 285.3-574.3 g, 144.1-663.2 g, 94.4-731.6 g and 18.1-430.7 g, both increasing with time, especially for grass carps. Over the five year investigation, the main area of FMCCS habitation gradually moved from the section of Fuling to Zigui, towards the middle sections, Zigui and Yunyang. From the five sections sampled, the number and weight of the FMCCS catches were highest in the Yunyang section. Impact analysis showed that the main problems faced by FMCCS in TGR are changes in the hydrologic regime resulting from the cascaded hydropower stations on the Jinsha River, and widespread overfishing in TGR.