Abstract:

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 positively 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 of H. brachyrostralis along the Yangtze River basin.