Ecological health assessment of the Yangtze Estuary based on fish index of biological integrity(F-IBI)
To assess the ecological health status of the Yangtze Estuary,the biological integrity index was constructed using fish survey data from 14 stations in the Yangtze Estuary from May 2018 to November 2020.Available data and applicability to ecosystem types and geographic area was considered,five categories were selected including species compositions and abundance,tolerance,trophic structure,reproductive guild,and fish healthy status.A total of 30 candidate indicators in terms of quantity and quality,and 14 evaluation indicators were screened out.The best recorded historical state was used as the reference value,and the indicators were assigned according to the degree of survey value deviation from the reference value.Based on fish index biological integrity(F-IBI),results showed that the F-IBI score of each station in the Yangtze Estuary ranged from 25 to 66,and the evaluation grades ranged from poor to general.The overall health status demonstrated that the estuarine mouth was better than the estuary section,and the north branch was better than the south branch.The differences in scores among different areas were mainly caused by difference in the total number of fish and the degree of pollution and destruction of spawning grounds.The reasons were as follows:1)The south branch of the Yangtze River was the main channel for the runoff to the East China Sea;land-based pollutant discharge also brought a large number of heavy metals,and the pollution in the estuary was serious than the mouth.2)In recent years,the runoff of the Yangtze River had decreased,and the south branch was greatly affected by fresh water runoff,so the influence degree was south branch＞north branch＞mouth of estuary.3)Human activities are more frequent in the south branch.The overall F-IBI score of the Yangtze Estuary was 44,evaluated as poor.The important factors restricting the score were the decreasing of total fish species and biomass,the proportion of migratory fish and swimming creature feeding fish,and the increase of the proportion of tolerant fish and mixed-feeding fish.In summation,the study revealed that the biological integrity of the Yangtze Estuary was severely damaged:1)The structure of fish community was unreasonable,and the proportion of settled fish increased due to the sharp decreasing of migratory fish,marine fish and freshwater fish,and the fish biomass was low and the habitat conditions were poor;2)The proportion of tolerant fish increased significantly,and water quality deteriorated seriously;3)The proportion of fish producing floating egg decreased,and the function of estuarine spawning ground was destroyed;4)The nutritional structure changed,the proportion of swimming creature feeding fish decreased significantly,and the proportion of mixed-feeding fish increased.It is suggested that ecological restoration should be carried out by scientific multiplication and discharge,construction of alternative habitat and strict control of water-related project construction.
Yangtze Estuaryindex of biological integrityhealth statusecological evaluationfish
万方数据
维普
