River Health Assessment Of Dongjiang River Mainstream And Liuxi River Drainage Based On Fish Index Of Biotic Integrity(F-IBI)

Dongjiang is the third largest river system in the Pearl River basin and an important source of drinking water for cities such as Hong Kong,Guangzhou,Shenzhen,and Dongguan.Liuxihe is an tributary of the Beijiang River which is the second river system of the Pearl Rive,as the whole basin of Liuxi River is located in Guangzhou,it is regarded as the mother river of Guangzhou.In recent years,with the rapid socio-economic development,negative arthropogenic activities have caused the decline of fish resources in Dongjiang and Liuxi Rivers,and damaged the river ecosystems.In this study,F-IBI were used for river health assessment in the mainstream of the Dongjiang River and Liuxihe River drainage with the aim to provide scientific basis for fish resource sustainable exploitation and river ecosystem restoration decision-making,the results are as following:1)Dongjiang River Mainstream17 sampling sites of the Dongjiang River mainstream were surveyed for 8 times from November 2015 to October 2016.A total of 5007 inds were collected,and 12orders,26 families,80 genera,117 species were identified.Compared with 85 species of fish from 6 river reaches of the Dongjiang River reported in 2009-2011,82 species were shared,and 3 alien species Cyprinus haematopterus?Tilapip aureus?Piaractus brachypomus were added.Compared with the survey results in the 1980s,26historical recorded species were not collected,and 21 new records were added,the Jaccard?s similarity index between the two surveys was 0.50,indicating that the fish community composition in Dongjiang River mainstream had changed significantly.The G-F index shows that the species diversity of fishes in Dongjiang River mainstream has been reduced.The?diversity index in Guzhu town is the highest(C=0.97,H=3.83,E=0.90,R=10.49),and Shilong town is the lowest(C=0.83,H=2.15,E=0.76,R=3.38).The results of?diversity analysis showed that the composition of fish communities in different river reaches was significantly different,of which the difference between Fengshuba and Sidu was largest(?_C=21.0,?_L=70.0%,I=0.18,BC=0.89).Based on fish composition of the Dongjiang mainstream the 9 indexes F-IBI system were constructed to assess the health of Dongjiang River mainstream.The result showed that while Fengshuba?Laolong?Tuocheng?Yihe?Guzhu?Ruhu were ordinary,Dongshui?Sidu?Lankou Town and Yuancheng?Xiajiao?Boluo?Tonghu?Qiaotou and Qishi town were poor,and Linjiang and Shilong were extremely poor,which might have implied that fragmentation caused by the construction of cascade hydropower stations and water pollution etc had resulted in discontinuity of fish composition in the Dongjiang River.2)Liuxi River drainage3 sampling surveys were conducted on 9 site of the Liuxi River drainage from January 2016 to December 2017.A total of 2096 fish samples were collected,and 7 orders,17 families,63 genera,79 fish species were identified.Compared with recently reported Zhao's survey,15 recorded species were not collected,20 species were newly recorded,and the Jaccard?s similarity index between the two studies was only 0.62?The analysis of G-F index showed that the species diversity of fish in Liuxi River reduced.The?diversity index in the upper stream is lower than that thosed in the middle and lower stream.The results of?diversity analysis showed that the fish community in Liuxi River exhibited a pattern of vertical distribution,and the fish community varied among sampling sites.In particular,the difference between the upper reaches of the Sanyatang and the lower reaches of the Banghu Bridge was most significant(?_C=18.0,?_L=100.0%,I=0,BC=1.0).According to the characteristics of longitudinal distribution of fish communities and fish community structure in Liuxi River,4 and 7 indicators of F-IBI system were constructed to assess the upper and middle-lower reaches of Liuxi River respectively.The results showed that the river health of Xinlian?Lutian and Liangkou were good;Beixi?Sanyatang and Jiekou were ordinary;Bishuiwan?Taiping,and Banghu Bridge were poor,indicating that from the upstream to the downstream of the Liuxi River,the river health situation of the Liuxi River has gradually deteriorated with the increase of human activities.The F-IBI results showed that the health of the Dongjiang River and the Liuxi River were damaged,and the fishery resources declined to various degrees.The construction of cascade hydropower stations,environmental pollution,overfishing,and invasive alien species were supposed to be important factors that have damaged the ecosystem and fishery resources of the Dongjiang mainstream and the Liuxi River water ecosystem.