基于栖息地斑块尺度的青弋江河源溪流鱼类群落的时空格局

THE SPATIO-TEMPORAL DISTRIBUTION OF FISH POPULATION IN THE HEADWATERS OF THE QINGYI RIVER: A STUDY BASED ON THE HABITAT PATCHS

确定鱼类的栖息地利用格局是研究物种与环境关系的基础,也是鱼类多样性保护和管理的必要前提。目前,有关溪流鱼类群落的栖息地斑块利用格局尚存在争议。基于2012年9月至2013年8月对青弋江河源溪流的逐月调查数据,初步研究了鱼类群落的栖息地斑块利用格局,着重在栖息地斑块尺度上解析了鱼类群落的时空变化规律。主要研究结果显示,深潭和急滩2类斑块间的底质、流速、水深、溶氧栖息地因子显著差异,且深潭斑块的环境稳定性高于急滩。研究共采集鱼类15种,其中鲤科鱼类8种,占采集物种数50%以上。基于鱼类物种存在与否的不连续变量的分析结果显示,鱼类物种组成的斑块间和月份间变化均不具显著性。但是,基于鱼类物种多度的连续变量的分析结果显示,鱼类群落结构存在有显著的斑块间变化和时间动态;就斑块间变化而言,原缨口鳅(Vanmanenia stenosoma)在急滩斑块中的多度更高,而宽鳍(Zacco platypus)、光唇鱼(Acrossocheilus fasciatus)和尖头(Phoxinus oxycephalus)等其他关键物种则在深潭中具有更高多度。深潭斑块的鱼类物种数显著高于急滩,但2类斑块间的个体数无显著差异。深潭斑块的鱼类物种数较稳定,而个体数月变化显著,可能与鱼类繁殖和群体补充以及越冬死亡等有关;急滩鱼类物种数和个体数的月变化均显著,除了与鱼类群体补充和越冬死亡有关以外,还可能受越冬时栖息地斑块选择变化的影响。上述结果表明,在栖息地斑块空间尺度上,由于研究区域内大多数物种在栖息地斑块选择上无明显的特化性,深潭和急滩斑块间鱼类的物种组成分布不符合前人所报道的"生境-共位群"格局,但区域内常见种多度的变化可引起鱼类群落结构的斑块间差异和季节动态。

The knowledge on the habitual preference of stream fish is the key to understand the species-environment relationship and is important for the protection and management of the diversity in fish. However, to date it is still unclear how a fish population varies in different habitat patches in the shallow streams. In this study, we investigated the fish species diversity and the population structures in different patches and months in local habitual conditions, based on the data collected monthly in 10 habitat patches（involving five pools and five riffles） in the headwaters of the Qingyi River from September 2012 to August 2013. The principal component analysis showed that pools and riffles varied substantially in local habitual conditions, such as the substrate size, the current velocity, the water depth and the concentration of dissolved oxygen. According to the results of paired t-test, the coefficients of the variability of the water depth, the current velocity and the concentration of dissolved oxygen in the riffles were significantly higher than those in the pools. This suggested that the habitual conditions in the pools were more stable than those in the riffles. Fifteen species were collected including 8 species of Cyprinidae fish that accounted for more than 50% of the entire samples in this study. We applied two-way crossed ANOSIM based on discontinuous variables of the occurrence of fish and found that the habitat patches and time（months） did not significantly affect the species composition. However, analysis based on continuous variables of the abundance of each species showed that the assemblage structure varied significantly in different patches and months. We performed SIMPER analysis to identify the key species that contributed to the inter-patch dissimilarity of the assemblage structure, and found that Vanmanenia stenosoma was more abundant in the riffles, and that other seven key species（e.g., Zacco platypus, Acrossocheilus fasciatus and Phoxinus oxycephalus） were more abundant in the pools. According to the results of ANOVA test there were more species in the pools than in the riffles, but there was no difference in fish abundance between the two patches. We observed that there were marked monthly changes in the fish abundance in the pools, and this may be associated with the fish cohort recruitment and the overwintering death which caused an increase in the abundance in October and a decrease in December. We also found that both the diversity and the abundance of fish in the riffles varied significantly over months, which may be caused by the cohort recruitment and death, as well as the overwintering shift in the habitat-patch. These suggested that in this area the distribution of fish species in different habitat patches might not conform to the conventional ‘habitat-guild＇ model because most fish species were habitat-generalists. However, the spatial and temporal changes in fish abundance may lead to a dynamic assemblage structure in different patches and months.