Annual variations of biotic integrity in the upper Yangtze River using an adapted index of biotic integrity (IBI)

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1 ecological indicators 8 (2008) available at journal homepage: Annual variations of biotic integrity in the upper Yangtze River using an adapted index of biotic integrity (IBI) Di Zhu a,b,c,1, Jianbo Chang a,b,c, * a Institute of Hydrobiology, Chinese Academy of Sciences, 7# Southern Road of East Lake, Wuhan, Hubei Province, China b Institute of Hydroecology, Ministry of Water Resources and Chinese Academy of Sciences, 578# Xiongchu Avenue, Wuhan, Hubei Province, China c The Graduate School of the Chinese Academy of Sciences, Beijing China article info Article history: Received 15 February 2007 Received in revised form 24 May 2007 Accepted 19 July 2007 Keywords: Fish assemblages Index biotic integrity (IBI) Three Gorges Dam (TGD) Upper Yangtze River abstract Adaptive modification and use of Karr s index of biotic integrity (IBI) for the upper Yangtze River, including 12 metrics in five categories, have typically occurred in line with the data collected by 6-year commercial fisheries investigation. These investigations were undertaken annually in four sections of the Upper Yangtze main channel between 1997 and These four monitoring sections (Yibin YB, Hejiang HJ, Mudong MD, and Yichang YC) were selected because they represent the part of the river that will be covering a 1000 km stretch that includes the future Three Gorges Reservoir (TGR), upstream of the Three Gorges Dam (TGD), an area influenced by the construction of TGD. In addition, historical data were used to show changes in the watershed by comparison with field investigations recently. The biotic integrity of the four sections were calculated and classified into different levels annually for recognizing its spatial and temporal variations. It was observed that IBI scores were becoming lower diminishingly since 1997 in all the four sections. Because all the data were collected before the impoundment of the Three Gorges Reservoir, it is obvious that human activities, especially over-fishing, must be crucial factor instead of damming in the upper Yangtze River in that period. # 2008 Published by Elsevier Ltd. 1. Introduction The index of biological integrity (IBI) originally developed by Karr (1981) and established by Karr et al. (1986) had previously been used in the United States (Karr, 1999a; Karr et al., 1986; Karr, 1999b) and became increasingly adaptive elsewhere, e.g. in Europe (Simon and Sanders, 1999). Many groups of organisms had been used as indicators to estimate environmental quality. Algae, benthic invertebrates and fish were typical species in biological monitoring (Matthews et al., 1982; Van Dolah et al., 1999). Fish assemblages were considered to be an appropriate end-point for assessing stream integrity due to their high public visibility, their position in the food chain and high sensitivity to water quality (Karr, 1981; Karr et al., 1986). Human influences, such as changes in water chemistry or physical habitat modifications, could alter fish assemblages by disrupting their structures and functions (Fig. 1). Varieties in fish assemblage could be detected through changes in components of the community, functional groups, species diversity, and relative abundance (Wootton, 1990). The fish-ibi * Corresponding author at: Institute of Hydroecology, Ministry of Water Resources and Chinese Academy of Sciences, 578# Xiongchu Avenue, Wuhan, Hubei Province, China; Tel.: address: jbchang@mail.ihe.ac.cn (J. Chang). 1 Main research fields: Ecology of Fishes and Conservation Biology, Aquatic Ecosystem Health Assessment X/$ see front matter # 2008 Published by Elsevier Ltd. doi: /j.ecolind

2 ecological indicators 8 (2008) Fig. 1 Aftermath of river basin environmental structure changes. was commonly used and accepted worldwide as a reliable tool to assess water condition now (Novotny et al., 2005). The IBI had become a family of multi-metric indices that were regionally adapted and calibrated, because rivers of different regions, as well as their fish communities, were distinctive (Kesminas and Virbickas, 2000). Despite many outstanding works on IBI had already been done (Novotny et al., 2005; Simon et al., 2000), it was still of utmost importance for us to continue this work in Chinese Yangtze River basin. The objectives of this study were to: (a) develop potential metrics of fish indicator for the upper Yangtze River; (b) quantify fish assemblage differences in the early 6 years of Three Gorges Dam (TGD) construction; and (c) provide a baseline for future water quality assessment in the upper Yangtze River. 2. Materials and methods 2.1. Study area The River is the third longest river in the world; its total length is about 6300 km with a basin area of about 180,000 km 2. The river is distinctive in its species diversity and abundance, while comprising the largest components of the fish resources in China (Chang, 1999; Wu, 2003; Young, 2003). However, the Yangtze River has experienced major changes over the past decades (Chang, 1999). Most of the water resources are disproportionately degraded by human activities such as water pollution, agricultural land use and irrigation farming, dam construction and over-fishing (Chang, 1995; Young, 2003). These man-made impacts are now of highest concern with regard to the disruption of the integrity of Chinese inland waters (J.B. Chang, 1999; Chang, 1999). River damming is the most dramatic anthropogenic factor affecting freshwater environments (Baxter, 1997; Dudgeon, 2000). The Gezhouba Dam was constructed in 1981 and has led to sharp declines in the populations of migratory fish previously occurring in great numbers in the upper Yangtze River, especially the three endemic ancient fish species, Chinese sturgeon (Acipenser sinensis), River sturgeon (A. dabryanus), and Chinese paddlefish (Psephurus gladius)(dudgeon, 2000; Xie, 2003; Young, 2003). The Three Gorges Dam (TGD) (38 km upstream from the TGD) is going to a massive human intervention which will fragment an area of about 58,000 km 2 with the formation of a reservoir of 1080 km 2 in an area of the former Yangtze River bed. This study reach of the river is influenced by TGD and is 1040 km long, including the main channel of the upper Yangtze River. Four monitoring stations were set up at different reaches, from the upper to the lower reach. These were at Yibing (YB), Hejiang (HJ), Mudong (MD) and Yichang (YC), respectively (Fig. 2). The Yibin (YB) station was located in Yibin county, covering a monitoring stretch of 21 km, including the lower reach of the Jinsha River. The Mudong (MD) station was located in Mudong town in a distance of 50 km from ChongQin City. The station represented a location at the deepest part of the TGD Reservoir. The monitoring reach covered a stretch of 30 km. The Hejiang (HJ) station was located in Hejiang county of the Sichuan Province with a monitoring stretch of 60 km. Finally, the Yichang (YC) station was located in Yichang City, with a monitoring reach of 25 km from Gezhouba Dam to Gulaobei Data collection methods and analyses Fishery investigations had been conducted in Yangtze River from 1950s till 2002 covering different reaches, together with the field investigations, these data provided very important baseline information, which were of tremendous value for assessment of ecological effects of human activities. The biological data ( ) were obtained from the TGD monitoring database of the Institute of Hydrobiology (IHB),

3 566 ecological indicators 8 (2008) Fig. 2 Study areas selected in the upper Yangtze River and distribution of four monitoring stations: Yibing (YB), Hejiang (HJ), Mudong (MD) and Yichang (YC). (TGD represent the location of Three Gorges Dam and GZD represent the location of Gezhouba Dam). Chinese Academy of Sciences (CAS). Most of the data were obtained by field investigations and others were derived from literatures. Twice investigations were conducted in May July and September December from 1997 to 2002 at the four monitoring stations. The duration of investigation was 20 days every time. The catches were collected from fishing boats and fish markets, the commercial fishing boats were sampled according to the principle of random sampling at each station. The information of fishing boat, fishing gears and fishing sites were recorded at the same time. At the four sites, fish collection was conducted according to the same method of commercial fishery investigation. Two main fishing gears (gill net, long-line) among others (casting net, electro-fisher, hoop net and seine) were found in the investigations in the upper Yangtze River. The mesh sizes of the gill nets ranged between 20 and 250 mm while the size compositions of catches generally portrayed the relative selectivity of the different mesh sizes. Long-line fishing was the capture of fish by entrapment of fishhook with bait or no bait, there was floating and demersal long-line, the fish inhabiting in different depth of river could be caught. Fishers who pursued maximal commercial benefits were believed to attempt to capture fish. All catches were collected and counted. Every fish specimen was measured, weighted, labeled and conserved in the formalin solution. Referring to the synopsis freshwater fishes of China (Ichthyologic Department, 1976) and The Fishes of Yangtze Rive (Zhu, 1995), fish specimens were identified. Fish were sampled and dissected proportionally to study the parasite and the availability of anomalies and get information in detail. We employed a linear regression to determine if the IBI scores of four sections were significantly change trend during that period Reference conditions derived Reference condition was a critical element of IBI to assess the quality or health of the aquatic ecosystem (Karr, 1981; Karr et al., 1986). The establishment of reference condition was based on identification of minimally disturbed sites that represent the best physical, chemical, and biological conditions. We modified the index and developed biological expectation for the upper Yangtze River fish assemblages. These expectations were developed with the assumption that least impact conditions would emerge from the cumulative data set. Yangtze Rivers has been dammed, channeled and dredged. Also, it is home to large urban areas and numerous point source dischargers, not to mention being the ultimate repository for non-point source inputs. As a result of these perturbations, reference condition is rare, and may be absent in so developed river. The reference expectations used in the paper were derived from the historical data, which came from database of IHB, CAS and some came from literatures and unpublished data, including our own observations. 3. Results 3.1. Fish assemblages Appearing within four river reaches the following numbers of fish species had been recorded: 97 in YB, 120 in HJ, 91 in MD, and 116 in YC (Table 1). The characteristics of fish assemblages of upper Yangtze River had been described including structure, tolerance, main trophic guilds, and appearance in investigations Development of an IBI for the upper Yangtze River A variety of potential IBI metrics were considered, including many from existing studies in lakes (Zhu and Chang, 2004) and others (Chang and Cao, 1999; Young et al., 2003) who suggested a unique fish fauna for the Yangtze River. Candidate metrics of IBI have been identified according to the original IBI (Karr et al., 1986) as well as IBIs applications elsewhere (Hughes, 1999; Lyons et al., 2000; Oberdorff and Hughes, 1992). Finally preliminary metrics were selected based on their broad applicability and stability across the previous studies and their consistent related to environmental degradation. Twelve

4 ecological indicators 8 (2008) Table 1 Occurrence of native fish species in the upper Yangtze River basin with indication of their trophic guilds (BI = benthic insectivores; O = omnivores; C = carnivores), environmental tolerance (T = tolerance) and others (CIS = commercial interests species; E = endemic species; Y = yes; * = presence) with MC = main channel; YB = Yibin, HJ = Hejiang, MD = Mudong and YC = Yichang Species CIS T Feeding MC YB HJ MD YC Abbotina obtusirostris Wu et Wang E * * Abbotina rivularis (Basilewsky) * * * * * Acheilognathus chankaensis (Dybowski) * * Acheilognathus gracilis Nichols * * Acheilognathus macropterus (Bleeker) * * * * Acipenser dabryanus Duméril E BI * * * * * Acipenser sinensis Gray BI * * * * * Acrossocheilus monticola (Günther) E BI * * * * * Acrossocheilus yunnanensis (Regan) * * Ancherythroculter kurematsui (Kimura) E C * * * * * Ancherythroculter nigrocauda Yih et Woo E C * * * Anguilla japonica Temminck et Schlegel C * * * Aphyocypris chinensis Günther * * * * * Aristichthys nobilis (Richardson) * * * Botia reevesae Chang E * * * Botia superciliaris Günther * * * * Culter dabryi Bleeker * * Culter alburnus Basilewsky * Culter mongolicus mongolicus (Basilewsky) * Carassius auratus (Linnaeus) Y T O * * * * * Channa argus (Cantor) C * * * * Cobitis sinensis Sauvage et Dabry * * Coilia brachygnathus BI * * Coreius guichenoti (Sauvage et Dabry) E Y T BI * * * * * Coreius heterodon (Bleeker) Y BI * * * * * Ctenopharyngodon idellus (Cuvier et Valenciennes) Y * * * * * Culter alburnus Basilewsky C * * * * * Culter mongolicus mongolicus (Basilewsky) C * * * * Culter oxycephaloides Kreyenberg et Pappenheim C * * * * * Culter oxycephalus Bleeker C * * * * * Cultrichthys erythropterus (Basilewsky) C * * * * * Cyprinus (Cyprinus) carpio Linnaeus Y T O * * * * * Elopichthys bambusa (Richardson) C * * * * * Euchiloglanis davidi (Sauvage) E BI * * * * * Euchiloglanis kishinouyei Kimura E BI * * * * * Fufu obscurus * * Garra pingi pingi (Tchang) Y * * Glyptothorax fukianensis (Rendahl) * * * * Glyptothorax sinense (Regan) BI * * * * * Gnathopogon imberbis (Sauvage et Dabry) BI * * * * * Gobiobotia filifer (Garman) Y BI * * * * * Hemibarbus labeo (Pallas) BI * * * * * Hemibarbus maculatus Bleeker BI * * * * * Hemiculter bleekeri Warpachowski * * * * * Hemiculter leucisculus (Basilewsky) * * * * * Hemiculter tchangi Fang * * * Hemiculterella sauvagei Warpachowski E * * Hemiirhamphus kurumeus * * Hemisalanx brachyrostralis (Fang) * * Hypophthalmichthys molitrix (Cuvier et Valenciennes) * * * * * Jinshaia abbreviata (Günther) E * * * Jinshaia sinensis (Sauvage et Dabry) E * * * * * Leiocassis crassilabris Günther Y BI * * * * Leiocassis longirostris Günther Y C * * * * * Leptobotia elongata (Bleeker) E Y T C * * * * * Leptobotia microphthalma Fu et Ye E BI * * * * * Leptobotia pellegrini Fang C * * * * * Leptobotia rubrilabris (Dabry) E C * * * * Leptobotia taeniops (Sauvage) C * * * * * Lepturichthys fimbriata (Günther) * * * * * Liobagrus marginatus (Bleeker) BI * * * * * Macropodus chinensis (Bloch) * *

5 568 ecological indicators 8 (2008) Table 1 (Continued ) Species CIS T Feeding MC YB HJ MD YC Macropodus opercularis (Linnaeus) * * * * Macrura reevesii * * Megalobrama pellegrini (Tchang) E T O * * * * * Megalobrama pellegrini (Tchang) * * Micropercops swinhonis (Günther) * * * Misgurnus anguillicaudatus (Cantor) O * * * * * Monopterus albus (Zuiew) BI * * * * * Mylopharyngodon piceus (Richardson) BI * * * * * Mystus macropterus (Bleeker) BI * * * * * Myxocyprinus asiaticus (Bleeker) BI * * * * Neosalanx taihuensis Chen * * * Ochetobius elongatus (Kner) BI * * * * * Odontobutis obscurus (Temminck et Schlegel) * * Onychostoma sima (Sauvage et Dabry) * * * * * Opsariichthys bidens Günther C * * * * * Oryzias latipes (Temminck et Schlegel) * * Parabotia fasciata Dabry BI * * * * * Parabramis pekinensis (Basilewsky) * * * * * Paracheilognathus imberbis * * * Paracobitis potanini (Günther) E T BI * * Paracobitis variegatus (Sauvage et Dabry) BI * * * Paramisgurnus dabryanus Sauvage O * * * * * Pelteobagrus fulvidraco (Richardson) T C * * * * * Pelteobagrus nitidus (Sauvage et Dabry) Y BI * * * * * Pelteobagrus vachelli (Richardson) Y T BI * * * * * Percocypris pingi pingi (Tchang) E C * * * * * Phoxinus oxycephalus (Sauvage et Dabry) BI * * * * * Platysmacheilus nudiventris Lo, Yao et Chen E * * * Procypris rabaudi (Tchang) E Y T O * * * * * Psephurus gladius (Martens) C * * * * * Pseudobagrus brevicaudatus (Wu) Y BI * * * * * Pseudobagrus emarginatus (Regan) BI * * * * Pseudobagrus pratti (Günther) BI * * * * * Pseudobagrus tenuis (Günther) BI * * * * * Pseudobagrus truncatus (Regan) BI * * * Pseudobagrus ussuriensis (Dybowski) BI * * * * * Pseudobrama simoni (Bleeker) * * * * Pseudolaubuca engraulis (Nichols) O * * * * * Pseudorasbora parva (Temminck et Schlegel) T * * * * * Rhinogobio cylindricus Günther E Y T BI * * * * * Rhinogobio typus Bleeker Y T BI * * * * * Rhinogobio ventralis (Sauvage et Dabry) E Y BI * * * * Rhinogobius giurinus (Rutter) BI * * * * * Rhodeus lighti (Wu) * * * Rhodeus ocellatus (Kner) * * * * * Rhodeus sinensis Günther T * * * * Sarcocheilichthys nigripinnis (Günther) * * * Sarcocheilichthys sinensis Bleeker BI * * * * * Saurogobio dabryi Bleeker Y T * * * * Saurogobio dumerili Bleeker BI * * * * * Saurogobio gymnocheilus Lo, Yao et Chen * * * Schizothorax (Racoma) davidi (Sauvage) BI * * * * * Schizothorax (Schizothorax) chongi (Fang) E * * * * Schizothorax (Schizothorax) prenanti (Tchang) E * * * * * Semilabeo prochilus (Sauvage et Dabry) * * * * * Silurus asotus Linnaeus Y C * * * * * Silurus meridionalis Chen Y C * * * * * Sinilabeo rendahli (Kimura) E T * * * Siniperca chuatsi (Basilewsky) Y C * * * * * Siniperca kneri Garman C * * * * * Siniperca scherzeri Steindachner C * * * * * Sinogastromyzon sichangensis Chang * * Sinogastromyzon szechuanensis szechuanensis Fang E * * * * * Spinibarbus sinensis (Bleeker) Y O * * * * * Squalidus argentatus (Sauvage et Dabry) Y BI * * * * * Squalidus wolterstorffi O * * * *

6 ecological indicators 8 (2008) Table 1 (Continued ) Species CIS T Feeding MC YB HJ MD YC Squaliobarbus curriculus (Richardson) O * * * * * Tor (Folifer) brevifilis brevifilis (Peters) BI * * * * * Toxabramis swinhonis Günther * * * * Xenocypris argentea Günther * * * Xenocypris fangi Tchang E * * * Xenocypris microlepis Bleeker * * * * Xenocypris yunnanensis Nichols E * * * * * Xenocyprisdavidi Bleeker * * * * Xenophysogobio boulengeri Tchang E T BI * * * * * Xenophysogobio nudicorpa Huang et Zhang E * * * Zacco platypus (Temminck et Schlegel) O * * * * L.marginatoides E * * * Total metrics, which best represent the fish assemblages characteristics and the patterns of degradation in upper Yangtze River, are obtained and described below (Table 2) Species richness and composition The number of species is plotted against the sites, which give a more reliable measure of the species richness adjusted to employee fishing effort. We, therefore, followed Hughes and Oberdorff (1999) and Karr et al. (1986) in favoring only native species versus all species for this metric involved in the study. This is because the total native species in the upper Yangtze River are included in the calculations of the expected richness. The number of native species is a measure of biological diversity that typically decreases with increased degradation of habitat while not considering the undesirable influence of alien species, although they may affect native species. Cyprinidae, Bagridae catfishes, and Cobitidae are very common in Yangtze River, sometimes comprising the groups of fishes thriving under such harsh conditions (Zhu and Chang, 2004) Tolerant/intolerant species These fishes were considered as very tolerant species to be able to accommodate a variety of environmental conditions because they were very common in the catches of most sections, especially for the crucian carp are thought most tolerant to many pollutants. In this author s opinion, several carps should be classified as the most tolerant species, not just crucian carp. A good example is carp which is not only tolerant to a wide array of physical disturbances, but it is one of the few species that is known to be tolerant to a broad array of toxicants (e.g., ammonia, chlorine, heavy metals). This metric is the complement to number of intolerant species and is comparable to Hughes and Oberdorff s percent tolerant individuals (Hughes, 1999). Like Karr s (Karr, 1981) original percent green sunfish metric, it distinguishes between low and moderate water quality. Intolerant species (Karr and Fausch, 1986; Lyons et al., 2000) are that previously very abundant but presently occurs only occasionally because of environmental deterioration. Intolerant species are also sensitive to many types of environmental stressed and tend to be absent in the presence of environmental degradation (high suspended solids, increased temperatures and siltation, decreased dissolved oxygen), and are the last to reappear after restoration. Number of families in fishery catches is chosen as a metric of intolerance adversely, it will become more in a better quality of ecosystem Trophic guilds Trophic groups selected include benthic insectivorous, omnivores, and carnivores. Criteria separating these groups are not Table 2 Metrics and scoring criteria used in the IBI for the upper Yangtze River Attributes Metrics IBI scoring Species richness and composition %total number of native fish species >50% 30 50% <30% %number of species in the family Cyprinidae >50% 25 50% <25% %number of species in Bagridae catfishes >15% 5 15% <5% %number of species in the family Cobitidae >20% 5 20% <5% Intolerance and tolerance Percent of tolerance individuals < 6% 6 12% >12% Number of families in fishery catches > <12 Trophic guilds Percent of omnivores individuals <8% 8 15% >15% Percent of benthic insectivorous individuals >40% 20 40% <20% Percent of top carnivores individuals >15% 5 15% <5% Abundance Catch per unit effort (CPUE, Kg/boat) >2 1 2 <1 Individual condition Percent of non-native fish species <1% 1 2% >2% Percent individuals with DELT <2% 2 5% >5%

7 570 ecological indicators 8 (2008) sharply defined. Adults of omnivorous species proposed by Karr (1981) eat large proportions of both plants and animals for assessing disruption of the food web by stressors. We choose omnivores because they tolerate poor conditions. Top carnivorous adults eat predominantly other fishes or large invertebrates for assessing loss of trophic diversity and keystone species (Lyons et al., 2000). Percent of benthic insectivorous individuals is used for assessing disruptions in secondary production, because invertebrates are responsible for much of the processing of organic matter in rivers. Disrupted invertebrate biomass and composition is presumably reflected in disruptions in insectivorous fishes. Those metrics are also widely used in IBIs (Hughes, 1999) Abundance Catch per unit effort (CPUE), average catches of a fishing boat, is a measure of relative fish abundance as a substitute of the metric-relative number of individuals in the original IBI (Karr et al., 1986; Zhu and Chang, 2004), which evaluate fish populations within a stream or river site. Human activities, such as over-fishing will expectedly result in lower CPUE in the inland river. It is so reliable that it can be used to evaluate the fishery resource and fish abundance of in the Yangtze River Percent of non-native fish species Fish assemblages are considered to be biological integrity if no disturbance occurred. The presence of non-native fish species is considered as a disturbance factor (Ganasan and Hughes, 1998; Lyons et al., 2000). Alien species are mostly accidental releases from fish farms, these species could alter the structure of native fish assemblages by competition and predation, sometimes extirpate some native species. Consequently, the IBI should be negatively correlated with the quantity of non-native fish species present Percent individuals with DELT Fish with abnormalities are rare in good ecosystem, but the number of abnormalities will increase with the human activities increases, so we continue to use the metric for assessing conditions of fish individuals. External anomalies includes deformities, eroded fins, lesions, tumors, diseases, and parasites (DELT) (Karr et al., 1986). The presence of external anomalies indicates sublethal environmental stresses, intermittent stresses, behavioral stresses, or chemically contaminated substrates (Lyons et al., 2000) IBI values The IBI scores were becoming lower statistically in the 6-year scales and most IBI scores were classed as good and fair quality (Fig. 3). The result of linear regression analysis showed that the obvious degenerative trend in the biotic integrity for some uncertain reasons, but the increased human activities must be very important influencing factors. Fig. 3 Observed IBI scores for four upper Yangtze River, YC (open circles), MD (squares), YB (left triangles) and HJ (right triangles) are plotted against years between 1997 and The straight line shows the linear regression between year and IBI scores. headwaters to estuary. Those downstream changes can be described by longitudinal zonation concepts (Bram, 2003). Most fish species find suitable living conditions in only a selected stretch of the entire river. Already in the 19th century ichthyologists used this observation as the basis of a zonation system for river courses (Holčík, 1989), and the entire Yangtze River can be divided into several fishes zones. The upper Yangtze River was thought within the same fishes zone with its own ecological characterizations (Chang and Cao, 1999). The IBI is a regional index of analyzing and monitoring the impact of human disturbance (Fig. 1) on the structure of the fish assemblages by comparing community structure of the present state with that of the reference situation. The regional-based reference condition can be derived from an aggregate of reference sites or some empirical model of expectations and may include knowledge of historical condition or extrapolation from ecological principles (Lyons et al., 2000). In this paper, these expectations were developed with the assumption that least impact conditions would emerge from the cumulative data set without having to choose reference sites (Gammon and Simon, 2000). Most researchers, in the field of freshwater ecosystems, evaluated the environment degradation induced by human activities using the fish-ibi methodology (Araujo et al., 2003; Joy and Death, 2004; Paller et al., 2000). In his original description of the IBI (1981), as well as in later papers (Karr and Chu, 1999; Karr et al., 1986), Karr emphasizes the need for representative samples. In this paper, we used the data from fishery investigations instead of the standardized protocols (Karr et al., 1986) for the following reasons: 4. Discussion The physical, chemical and biological characteristics of natural large river changed gradually along its course from (1) The size of Yangtze River created many problems, fishes were much more migratory (both longitudinally and horizontally) and at any given time some species and many individuals were inaccessible because of depth (Simon and Sanders, 1999; Seegert, 2000a,b);

8 ecological indicators 8 (2008) (2) There were many kinds of freshwater fishes in Yangtze River, but human activities, particularly over-fishing, decreased the abundance. Field sampling with short time and small percentage of river cannot represent the entire reach; (3) Fishery catches collection was a preferred method for the large river in the evaluation of fish assemblages, and had been conducted in four sections as a long-term monitoring method. Because many riverine species regularly make long distance movements, particularly for spawning or overwintering. Long-term monitoring data and sampling period can minimize the confounding influence of such movements and avoid migratory periods as much as possible (Seegert, 2000b). It also benefited the comparison of spatial and temporal changes of the biotical integrity. Though these data might not be fully validated as the sampling methods had not been calibrated, the field survey itself may also contain some uncertainties. Therefore, it was believed that the data of 6-year period continuous survey were sufficient enough to reflect the actual conditions of the fish assemblages in the Yangtze River. It was also understood that the data obtained from extensive time series were sufficient enough to allow the first attempt to a modified IBI for evaluation on temporal and spatial changes of biological integrity within a large river. The IBI based on the fishery catches surveys need to be further tested and validated in many ecological areas with different fauna. This research revealed that the biotic integrity of the upper Yangtze River declined dramatically during The impact of river damming on aquatic ecosystem functioning had been documented (Baxter, 1997; Young et al., 2003). Damming and reservoir altered the flow regimes, from free-flowing to stagnant, and obstruct migratoryfishforwinterorfoodhorizontally.becauseall the data were collected before the impoundment of the Three Gorges Reservoir, it is obvious that human activities, especially over-fishing, must be crucial factor instead of damming in the upper Yangtze River in that period. In spite of that, the TGD is still the biggest hydroelectric dam in the world and entirely modified the main channel of the upper Yangtze River. The regulation of the TGD will alter water temperatures and chemistry, which in turn will influence the rates of biological and chemical processes. The reparation measurements should be employed in advance including (a) reinforcing the fishing management to reduce the extremely fishing; (b) constructing the nursery and conservation center; (c) captive propagation and releasing; and (d) building fish passage, e.g. the fish-ways. Acknowledgments We would like to express our appreciation to Prof. H. Rosenthal, Dr. Elijah M. Ntuli and Dr. C. Wolter for their insightful remarks and language editing. We are grateful to Zhiguo Miao, Shengguo Dan, Deqing Tan, Zhonghua Duan and Xuefu He for their great supports in field data collecting. This work was supported by National Natural Science Foundation of China (NSFC ) and Executive Office of State Council Three Gorges Project Construction Committee of China (SX , SX , SX ). references Araujo, F.G., Fichberg, I., Pinto, B.C.T., Peixoto, M.G., A preliminary index of biotic integrity for monitoring the condition of the Rio Paraiba do sul, southeast Brazil. Environ. Manage. 32 (4), Baxter, R.M., Enviromental effects of dams and impoundments. Annu. Rev. Ecology Systematics 8, Chang, J., Cao, W., Fishery significance of the rivercommunicating lake and strategies for the management of fish resources. Resour. Environ. 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