江湖阻隔对短吻间银鱼空间发生格局的影响

Impact of river-lake isolation on the spatial distribution pattern of Hemisalanx brachyrostralis

基于2001–2003年长江流域86个水体短吻间银鱼资源的连续调查,本文报道了短吻间银鱼(Hemisalanxbrachyrostralis)在流域尺度上的分布格局和年度动态,分析了其时空分布格局与湖泊面积和隔离因子间的关系,探讨了流域江-湖水网系统破碎化对短吻间银鱼种群结构和动态的影响。结果显示短吻间银鱼仅分布于葛洲坝以下的长江中下游,发生率低(年均21.3%),空间发生格局年度变动频率高,种群稳定性低。调查湖泊内目标种发生率、种群稳定性均与湖泊面积呈正相关关系,而与湖泊隔离系数呈负相关关系;三年的发生格局始终极显著地正相关于湖泊的面积因子,同时负相关于湖泊的隔离因子。表明江湖阻隔所引发的湖泊水面缩减和湖间隔离度增大对短吻间银鱼资源产生了深刻的影响,对其空间格局的形成贡献显著。

During 2001-2003, we conducted a survey on icefish resources in the Yangtze River basin, aiming to find out the impacts of habitat fragmentation on the population structure and dynamics of the species Hemisalanx brachyrostralis. By investigating the presence/absence of the target species in 86 water bodies, we analysed its temporal-spatial distribution patterns in relation to two important habitat parameters-water area and isolation. The results indicated that this species was mainly distributed in lakes affiliated with the mid-lower reaches of the Yangtze River, showing low incidence of occurrence （IO=21.3%, annual mean）, frequent change in spatial pattern, and unstable population structure from year to year. Further analysis showed that both the IO and population stability of this species related positively to the water area index but negatively to the isolation index of the lakes studied. Binary logistic regression elucidated the presence/absence structure of H. brachyrostralis in the three years, showing presence of the species was posi- tively related to water area index with high significance and negatively related to isolation index with significance. We conclude that the process of river-lake fragmentation, which results in the decrease of water area and increase of lake isolation, has major impacts on the spatial structure and dynamics ofH. brachyrostralis along the Yangtze River basin.