长江流域水域及消落区现状、变迁与渔业资源变动

采用中-大尺度遥感监测手段,对长江流域水域及消落区开展调查与分析,重点阐述长江流域从自然水体为主向人工水面为主的变化趋势,及其对长江流域天然渔业资源衰退的潜在影响。结果显示,近40年全长江流域历史最大水面约63 360 km²,最小水面约26 396 km²,历史最大消落面积约36 964 km²。2019—2020年“一江两湖七河”最大水面约为19 663 km²,最小水面约为14 281 km²,消落区面积6 337 km²,其中反季节性消落区633 km²。2001—2020年和1984—2000年两时段相比,地表水减少水面中超过80% 来自于具有自然水文情势的消落区,而新增水面中,由于水库充填导致的河流水面增加达5 500 km²,致使长江流域水域类型组成结构发生了巨大转变,自然水体占比不足20世纪80年代的一半,而同时期的鱼类资源现存量也下降为20世纪80年代的一半。本研究首次明确反季节性消落区的概念,探讨了长江流域河流梯级水库充填形成的反季节性消落区与鱼类“三场”(产卵场、索饵场和越冬场) 关键栖息地丧失的关系。

Status and transition of surface water fluctuation zones in the Yangtze River basin and fishery resource change

The water fluctuation zones are widely distributed in the Yangtze River Basin, with diverse types, different kinds of formation, various functions and complex habitats. The intensive analysis of the historical changes, current situation and component types of the water fluctuation zones is of great significance for maintaining the aquatic biodiversity and ecosystem balance along the banks of rivers and lakes, and protecting the ecological and environmental security of the Yangtze River system. In this paper, the medium-large scale remote sensing monitoring method is used to investigate and analyze the water area and the fluctuation area of the Yangtze River Basin, focusing on the change trend from the natural water body to the artificial water surface, and its potential impact on the decline of the natural fishery resources in the Yangtze River Basin. The results show that, in the past 40 years, the historical maximum water surface of the whole Yangtze River Basin is about 63,360 km², the minimum water surface is about 26,396 km², and the historical maximum ebb and flow area is about 36,964 km². From 2019 to 2020, the "One River, Two Lakes and Seven Rivers" region had a maximum water surface of 19,663 km², a minimum water surface of 14,281 km², and a fluctuation area of 6,337 km², including an anti-seasonal fluctuation area of 633 km². Compared to period of 2001-2020 and period 1984-2000, more than 80% of the reduction of surface water was due to the loss of the area of seasonal natural water fluctuation, while the increase that resulted from reservoir filling was up to 5500 km². As a result, the structure of water ecosystem in the Yangtze River basin changed dramatically. The proportion of natural water body and fish resources was less than half of that in the 1980s. Furthermore, this study clarified the concept of anti-seasonal artificial water fluctuation area for the first time, and investigated the relationship between the anti-seasonal artificial water fluctuation zone formed by the filling of cascade reservoirs in the Yangtze River Basin and the loss of fish critical habitat.