Fish assemblage status in Longyanhe river system, tributary of Zhihugang, Taihu Basin

In order to evaluate fish resource status in Zhihugang,gate-controlled inflow river of Lake Taihu,fish assemblage status in Longyanhe river system,main tributary of Zhihugang and their influencing factors were studied in August 2009 and May 2010 respectively.Results showed that a wide variety of fish species existed in the study area,and thirty two species of fish were collected,which belong to 22 genera,27 families and 5 orders.Species numbers of fish assemblages in spring and summer had not obvious difference;however,fish abundance and biomass in spring were both significantly higher than those in summer;species composition of fish assemblages in different locations,that is,main tributary,secondary tributary and tributary end,varied as well.Water transparency and dissolved oxygen content were positively correlated with abundances of Carassius auratus,Macropodus ocellatus and Macropodus opercularis,Water nutrient concentrations,i.e.,nitrogen and phosphorus,were negatively related to fish abundances of Pseudobrama simoni,Hemicculter leuciclus and Carassius auratus.Excess nutrient concentration and corresponding low water transparency and dissolved oxygen content produced an adverse effect on fish assemblage structure and species composition.