Relationships between fish richness, habitat diversity and channel parameters in gravel-bed streams in The East Tiaoxi River Basin, China (#120)
In gravel-bed rivers, there is a typical bed morphology composed of pool-riffle sequences, which provides important habitat for many aquatic organisms. This research show how habitat diversity important for fish diversity in gravel bed streams in China, where the information about freshwater fish habitat has been still limited. In addition, we revealed the relationship between habitat diversity and important channel parameters: width to depth ratio (Bm/Hm) and dimensionless shear stress (τ*).
Field survey was conducted at 18 reaches along four tributaries of the East Tiaoxi River, China, 2010. We caught freshwater fish at classified in-stream habitats (riffle, run, glide, pool, and backwaters) and measured some physical parameters. Multivariate analysis revealed the habitat preference of each captured fish species, and the significant correlation between fish richness and habitat diversity calculated based on the proportion of each habitat area. At the same time, habitat diversity increased as Bm/Hm increased until approximately Bm/Hm = 50~60, which is the boundary between single bar region and multiple one in some riverbed morphology criterion. However, there were two exceptions. Firstly, a meandering reach had high habitat diversity despite low Bm/Hm because of a different bar formation mechanism (i.e. fixed bar). Conversely, the dam or weir induced armouring reaches had low τ* (< 0.05) and lower habitat diversity than the other normal reaches having same Bm/Hm value. In conclusion, meandering and sufficient wide river reaches (Bm/Hm > 50) having well developed bars should be conserved, which would lead conservation of the rich fish fauna.