The Health Diagnosis Of Headwater Stream Based On Fish Cohort In Pihe River Catchment

China,one of the countries with the most extensive inland water area in the world,has extraordinarily rich rivers resources in its territory.But with the rapid development of China's economy,the surrounding land use type,urbanization,water conservancy construction and other human activities have resulted in the majority of the rivers suffering ecological degradation and environmental pollution in basins scacle.Thus the river health is under multiple threats,and in urgent need of an effective management tool for measure and remedy.As a biological evaluation tool to measure the river health,biological integrity means that biological communities have an ability to keep their inner-balance,maintain structural integrity and adapt to environmental changes.As a health evaluation system,the biological integrity,being is valid or not,depends on that it should not only reflect the extent of the ecological system suffering from environmental pressure,but also be able to distinguish the sources of pressure.Different from large rivers,the headwater streams are often located in mountainous,whose complex geological conditions and climatic changes make stream fish populations more sensitive and vulnerable when facing environmental changes and human disturbance,as a result of which,the risk of the stream fishs' endangering and even extinction is higher.In view of this,the Pihe River basin in Ta-pieh Mountain was chosen for study.Based on previous survey,the study will analyze the causes for the fishes' threats and diagnose the health of those streams with F-IBI,so as to determine the sources for their health pressure,and propose strategies for river conservation and management in study region.After a long-term specimen collection and data analysis,here are the findings in the following:1.Licensed from goverment,we fished with a backpack fishing gear in the wading area,used drift nets in the un-wading river and collected fishermen's catch from the stem river.Our study found that there were 43 fish species in total in the Pihe River basin,with 31 in the stem river,19 in western streams and 17 in eastern streams.The number of repeating species is 6 in whole catchment,and 9 in both the weastern and eastern basin.The number of fish species in the upper reaches of the streams was significantly less than that in the downstream stem streams.The most fishes were accustomed to live in middle or upper lays,and producing rafting eggs in stem river.And the streams in western and eastern mountains had the largest proportion of benthic species as well as yielding viscosity and sinking eggs species.The Liobagrus styani and Pelteobagrus eupogon in the level of CR(Critically Endangered),which occupies 4.7%in whole catchmen,and 86%species in the level of LC(Least Concern).In the survey,the fish culture by low-head dam,invasive species,hydrological instability,etc.were also found in the headwater stream,which had exerted an impact on fish population.2.Three times(April,August and October)survey of 25 stites had been sampled.The fishes,belonging to 4 orders,8 families,21 genus,23 species,were caught in the headwater stream of Pihe River.By using "scope","sensitivity" and "redundancy",four metrics including the "Shannon-Wiener index","the number of benthic fish species","the proportion of tolerant individuals" and "the number of omnivorous fish species(without tolerant)",were selected out of 49 candidate metrics to calculate F-IBI scores in each sample reach.Based on hypothesized reference points methods,each samping reach was consecutively scored.The results show as following:(1)The average F-IBI score of the west Pihe River was 19.35 points and that of the East Pihe River 20.65 points.(2)The F-IBI score of the 1st order was 20.58 points,the 2nd order 19.04 points,and the 3rd order 20.33..(3)The average F-IBI score sequence of samplings in different months was "April(17.54 points)<August(17.56 points)<October(19.18 points).Thus there was a spatio-temportal difference detected in Pihe River health evaluation.3.According to the results of health evaluation,the relationship between F-IBI scores and the factors including "habitat indicators","stream spatial positions" and "a visual-based habitat assessment" was analyzed.We found that a higher F-IBI score with more water depth,and a lower F-IBI score with faster current velocity in whole catechment scale.In 1st stream,a higher F-IBI score of reach normally has deeper water depth and wider stream width;If a reach with more faster current velocity,which more close to upstream,it will has a lower F-IBI score.The similar phenomenon has been shown in the 2nd streams.We also found that if there are more nutrients(higher conductivity)in the reachs of 2nd or 3rd stream,more fish resource and higher F-IBI score will been found in these reaches.In whole catchment,the fish in April should have been more concerned.The changes of the fish assemblage was mainly caused by the natural factors such as seasonal stream's "hydrological fluctuations","lengthways pattern”and "stream spatial positions".These factors led to that the health of the upstream area was mainly affected by the“local habitat",the downstream was mainly affected by the "stream spatial positions",and an obvious seasonal variation in whole study area.So a diagnosis can been drawn as follows.(1)The protection of the upstream in the high altitude areas of the whole basin should be attached importance to,and for the west Pihe River,more attention should be given to protecting the river habitat in the high-altitude middle reaches.(2)The water conservation of the 1st order streams should be noted,and in the upper reaches of all stream levels in the whole basin,the deep water area needs to be protected.(3)Attention should be paid to the streams at the downstream location with narrow channel and poor nutrition in April,streams at the upstream location in August,as well as streams with high altitude,narrow channel and high velocity in the middle position in October.Especially the protection of fishery resources in April needs to be strengthened.4.According to the autecologymatrix,the variation of the fish's habitat requirement in Pihe River catchment was analyzed.The results shown that the fish's habitat requirement,which between all sites in differ sampling time,is similar in whole area.But we also found some difference between them:In April,more muddy bottom,and still water with worst water quality;In August,there was more muddy or sandy sediment,slower current velocity and poor water quality;In October,more sandy riverbed,rapid current velocity and the best water quality.Compared with the eastern area,the western area has more muddy sediment and slower current velocity.The above conclusions were consistent with the results of the river health diagnosis.5.In order to find out the impact of the blocking river farming on fish assemblage,a small stream with the low-head dam was chosen as the sampling site to investigate.The habitat variables,the fish diversity and fish assemblage structure were surveyed for 6 times from 2013 to 2014 in these wadeable reaches of the sampling sites.The influences of temporal and spatial dynamic changes and local habitat conditions upon the fish assemblage was analysed,seasonal factors were found to have no apparent effect on the fish assemblage structure,while the spatial location(the upstream dam or the downstream dam)affected the assemblage's structural differences rather significantly,all the three habitat variables including dissolved oxygen,conductivity and current velocity exerted a great impact on the fish assemblage(P<0.05).The differences in habitat environment bring about some great influences on the fish assemblage,showing in the dramatic decrease of capture weight,quantity,density and diversity of fish in the sampling sites of the downstream dam,which are probably caused by the fish culture within the low-head dam.6.In order to understand the ecological harm of the invasive green sunfish(Lepomis cyanellus)in the Dabie Mountain area,we investigated the local water environment and found that the species had a colony of 22 with identified coordinates and lived mostly in reservoirs,ponds and a few upper streams with slower flow velocity.The anatomy of the digestive tract showed that the green sunfish was a typical carnivorous fish.Compared with the local stream fish,the green sunfish had a broader feeding,with food sources covering not only those creatures with crustaceans and screw-type protective shells,but also the terrestrial orthoptera.Then the fish were morphologically and structurally analyzed.The results showed that the males,with a shorter and broader tail were apt to live in spacious still waters,while young males and all the females,because of their longer tails,were more suitable for continuous movement in the flowing water.Therefore,the occupation of green sunfish in slow waters and rapids of the mountainous streams was comprehensive.Compared with the adjacent waters,green sunfish had seriously affected fish community in the waters they invaded,resulting in the decline of fish diversity and evenness.Green sunfish were strong in the ability of pollution tolerance and breeding,and had great potential in local invasion due to their invasive misdeeds in the place of their origin.Thus the prevention and control of the fish's invasion should be carried out as soon as possible,so that the unrecoverable damage to the local ecological system caused by the fish could be prevented.Summary,this study suggests thaht most fish species in the level of LC(Least Concern)in Pihe River catchment.The headwater stream health and fish distribution were mainly affected by natural condition;For more fish resource existed in the downstream,the health of the downstream was better than the upstream;the health affecting factors were subject to hydrological changes in the heatwater streams.Thus we should focus on the prevention and control of all kinds of fishing in summer,pay attention to the protection of river habitats,and prohibit quarrying and sand mining so as to protect the fish refuge in autumn and winter.Besides,we should attach importance to human disturbance in the 2nd order streams,then stre ngthen the vegetation protection and do water conservation.On a regional scale,the west Pihe River basin needs more protection.Moreover,we need to guard against fish culture by the lo w-head dam and potential threats of the invasive fish to local rivers and streams.