RELATIONSHIPS BETWEEN FISH RICHNESS, HABITAT DIVERSITY, AND CHANNEL PARAMETERS IN GRAVEL-BED STREAMS IN THE EAST TIAOXI RIVER BASIN, CHINA

In gravel-bed rivers, there is a typical riverbed morphology composed of pool-riffle sequences, which provides important habitat for many aquatic organisms. This research shows how habitat diversity influences fish diversity in gravel bed streams in China, where information about freshwater fish habitat has been still limited. In addition, we studied the relationship between habitat diversity and important channel parameters, width to depth ratio (B-m/H-m) and dimensionless shear stress (tau(*)). Field survey was conducted in 18 reaches along four tributaries of the East Tiaoxi River, China, in 2010. We caught freshwater fish within classified in-stream habitats (riffle, run, glide, pool, and backwaters) and measured some physical parameters. The GLM and single correlation analysis revealed the significant correlation between fish richness and habitat diversity calculated based on the proportion of each habitat area. Simultaneously, habitat diversity increased as Bm/Hm increased until approximately B-m/H-m = 50-60, which is the boundary between the single bar and multiple region in some riverbed morphology criterion. However, there were two exceptions. Firstly, a meandering reach had high habitat diversity despite low B-m/H-m because of a different bar formation mechanism (i.e. fixed bar). Conversely, the reaches with dam or weir induced armouring had low tau(*) (<0.05) and lower habitat diversity than the other reaches, even though both reaches have the same level of B-m/H-m value. In conclusion, meandering and sufficiently wide river reaches (B-m/H-m > 50) with well-developed bars should be conserved in order to support conservation of the rich fish fauna.