Conservation strategies for endemic fish species threatened by the Three Gorges Dam

The largest damming project to date, the Three Gorges Dam has been built along the Yangtze River (China), the most species-rich river in the Palearctic region. Among 162 species of fish inhabiting the main channel of the upper Yangtze, 44 are endemic and are therefore under serious threat of global extinction from the dam. Accordingly, it is urgently necessary to develop strategies to minimize the impacts of the drastic environmental changes associated with the dam. We sought to identify potential reserves for the endemic species among the 17 tributaries in the upper Yangtze, based on presence/absence data for the 44 endemic species. Potential reserves for the endemic species were identified by characterizing the distribution patterns of endemic species with an adaptive learning algorithm called a "self-organizing map" (SOM). Using this method, we also predicted occurrence probabilities of species in potential reserves based on the distribution patterns of communities. Considering both SOM model results and actual knowledge of the biology of the considered species, our results suggested that 24 species may survive in the tributaries, 14 have an uncertain future, and 6 have a high probability of becoming extinct after dam filling.

Structure of macrozoobenthos of the East Dongting nature reserve, with emphasis on relationships with environmental variables

Ecological survey of macrozoobenthos assemblages was carried out at 32 sites in the East Dongting Nature Reserve, located in the northern region of the East Dongting Lake in the middle basin of the Yangtze River, China. All total 51 taxa including 18 oligochaetes, 15 mollusks, 14 insects and four other animals were recorded. Mollusks composed the dominant group and accounted for more than 70% of the total abundance. Assemblages were composed mainly of scrapers (66.7%) and collector-gatherers (nearly 20%), and to a lesser extent collector-filterers (roughly 12%), predators (ca. 7%), and shredders (ca. 6%). Two-way indicator species analysis, detrended correspondence, and canonical correspondence analysis (CCA) were employed to identify the relationships between macrozoobenthos assemblages and environmental variables. Thirty-two sites were separated into four site groups based on composition and relative abundance of benthic macroinvertebrates. CCA detected that water depth, pH, conductivity, SiO2, total nitrogen, total phosphorus, alkalinity, hardness, and Ca2+, were significant environmental factors influencing the pattern of macozoobenthos. In this minimal subset, water depth, pH, alkalinity and hardness were the most influential variables.

Is the genus Digramma synonymous to the genus Ligula (Cestoda : Pseudophyllidea)? Evidence from ITS and 5 ' end 28S rDNA sequences

The genus Digramma (Cestoda: Pseudophyllidea) described by Cholodkovsky in 1915 differs from the genus Ligula only by the number of the reproductive organs per proglottis. However, the occurrence of transitional forms in Digramma raises much confusion concerning its generic validity. In the present study, cestodes previously designated as Digramma and Ligula were collected from lakes in the lower and middle reaches of the Yangtze River, and also from Qinghai Lake on Qingzang plateau, China. The entire internal transcribed spacer of the ribosomal DNA (ITS rDNA) and 5' end of 28S rDNA were compared between the Digramma and Ligula specimens. The low level of nucleotide variation between the two genera may imply that cestodes in the genus Digramma are paraphyletic to the Ligula genus, and Digramma is a synonym of Ligula. However, whether previously identified Digramma cestodes represent different species in the genus Ligula requires further investigation.

Comparative ontogenetic behavior and migration of kaluga, Huso dauricus, and Amur sturgeon, Acipenser schrenckii, from the Amur River

We conducted laboratory experiments with kaluga, Huso dauricus, and Amur sturgeon, Acipenser schrenckii, to develop a conceptual model of early behavior. We daily observed embryos (first life phase after hatching) and larvae (period initiating exogenous feeding) to day-30 (late larvae) for preference of bright habitat and cover, swimming distance above the bottom, up- and downstream movement, and diel activity. Day-0 embryos of both species strongly preferred bright, open habitat and initiated a strong, downstream migration that lasted 4 days (3 day peak) for kaluga and 3 days (2 day peak) for Amur sturgeon. Kaluga migrants swam far above the bottom (150 cm) on only 1 day and moved day and night; Amur sturgeon migrants swam far above the bottom (median 130 cm) during 3 days and were more nocturnal than kaluga. Post-migrant embryos of both species moved day and night, but Amur sturgeon used dark, cover habitat and swam closer to the bottom than kaluga. The larva period of both species began on day 7 (cumulative temperature degree-days, 192.0 for kaluga and 171.5 for Amur sturgeon). Larvae of both species preferred open habitat. Kaluga larvae strongly preferred bright habitat, initially swam far above the bottom (median 50-105 cm), and migrated downstream at night during days 10-16 (7-day migration). Amur sturgeon larvae strongly avoided illumination, had a mixed response to white substrate, swam 20-30 cm above the bottom during most days, and during days 12-34 (most of the larva period) moved downstream mostly at night (23-day migration). The embryo-larva migration style of the two species likely shows convergence of non-related species for a common style in response to environmental selection in the Amur River. The embryo-larva migration style of Amur sturgeon is unique among Acipenser yet studied.

Observations on two species of phyllodistomes (Trematoda : Gorgoderidae) from fishes of the Hubei Province, central China, with an erection of Neophyllodistomum gen. n.

Two rare trematode species so far reported in the genus Phyllodistomum Braun, 1899, P. pawlovskii (Zmeev, 1936) and P. serrispatula Chin, 1963, were found in the urinary system the yellow catfish Pelteobagrus fulvidraco (Richardson) of Bao'an Lake (prevalence 8 %) and the swamp eel Monopterus albus (Zouiev) of Liangzi Lake (prevalence 6 9/6), respectively, from the Hubei Province, central China. In contrast to the original description, P. pawlovskii showed a considerable morphological variability particularly in the shape, size and topography of testes. A unique morphological feature of P. serrispatula is the presence of many conspicuous lateral outgrowths on the hindbody and, principally based on this character, a new genus Neophyl-lodistomum is erected (type species N. serrispatula (Chin, 1963) comb. n.)) to accommodate this species. Both trematode species are briefly redescribed. P. pawlovskii and N. serrispatula are reported for the first time from the Hubei Province and the former from the Yangtze River drainage system.

Distribution of epilithic algae in the Xiangxi River system and their relationships with environmental factors

The spatial pattern of epilithic algae in the Xiangxi River system was studied in relation to several environmental factors by two-way indictor species analysis (TWINSPAN), detrended correspondence analysis (DCA), and canonical correspondence analysis (CCA). Eighty-nine taxa including diatoms, green algae, and blue-green algae were observed. Diatoms were dominant, and Cocconeis placentula, Cymbella minuta, Diatoma vulgare, and Gomphonema angustatum appeared in most of sampling sites. By TWINSPAN and DCA, thirty-one sites were divided into three groups based on composition and relative richness of benthic algae. CCA indicated that SiO2, pH, total phosphorus, Ca2+, velocity, elevation, and Cl- were significant environmental factors affecting the distribution of algae communities. In this minimal subset, SiO2 and pH were the most influential variables.

Small fish communities in two regions of the Liangzi Lake, China, with or without submersed macrophytes

Small fish communities were compared between the vegetated and vegetation-free regions of the Liangzi Lake, a shallow lake along the middle reach of the Yangtze River, China. Fish were sampled using 10 x 10 m(2) block nets and poisoning. Three samples were taken from either the near shore area or lake centre of each region. A total of 19 fish species were collected; all species occurred in the vegetated region but only 12 occurred in the vegetation-free region. The dominant small fish were Carassius auratus auratus in the vegetated region and Ctenogobius giurinus in the vegetation-free region. Diversity, density and biomass of small fishes were significantly higher in the vegetated region than in the vegetation-free region in both near shore and lake centre areas. In the vegetated region, density and biomass of small fishes was significantly higher, while species diversity significantly lower in the near shore area than in the lake centre. In the vegetation-free region, density of small fishes was significantly higher in the near shore area than in the lake centre area, but species diversity or biomass was unaffected by location.

Impact of eutrophication on biodiversity of the macrozoobenthos community in a Chinese shallow lake

Comparative studies on community structure and biodiversity of macrozoobenthos were carried out in three lake areas with different states of eutrophication (mesotrophic, eutrophic and hypereutrophic) in a shallow subtropic lake (Lake Donghu) in the middle basin of the Yangtze River of China. Thirty-three taxa (including six Mollusca, five Oligochaeta, 15 Chironomidae and seven other zoobenthos) were found during February 1998 to April 1999. The results show that the more eutrophic the lake water, the lower the macrozoobenthos species diversity (measured as species number, diversity index, and K-dominant curves). Abundance of the oligochaete Limnodrilus hoffmeisteri was positively correlated with the degree of eutrophication, which was due mainly to its ability to tolerate low dissolved oxygen. The chironomid Tanypus chinensis also thrived in the hypereutrophic environment; however, it was less endurable to eutrophication than L. hoffmeisteri.

WATER-QUALITY CHANGES AND EFFECTS ON FISH POPULATIONS IN THE HANJIANG RIVER, CHINA, FOLLOWING HYDROELECTRIC DAM CONSTRUCTION

Since its completion in 1973 the Danjiangkou Dam has markedly changed downstream flows, water levels, temperatures, sediment loads and other water quality characteristics in downstream reaches of the Hanjiang River. There have been changes in the growth, spawning behaviour and overwintering condition of local fish populations, in the composition and abundance of food organisms and in the composition of the commercial fish catch. Despite the changed environment and the absence of a fish pass, fish populations are still able to grow and spawn under the new regime. Where conditions are like those of the Hanjiang River, dams may not necessarily have calamitous consequences for fishery production.

Investigation on Fe, Mn, Zn, Cu, Pb and Cd fractions in the natural surface coatings sampled and surficial sediments collected in the Songhua River, China

Natural surface coatings sampled (NSCSs) from the surface of shingles and surficial sediments (SSs) in the Songhua River, China were employed to investigate the similarities and difference in fractions of heavy metals (Fe, Mn, Zn, Cu, Pb, and Cd) between NSCSs and SSs using the modified sequential extraction procedure (MSEP). The results show that the differences between NSCSs and SSs in Fe fractions were insignificant and Fe was dominantly present as residual phase (76.22% for NSCSs and 80.88% for SSs) and Fe-oxides phase (20.33% for NSCSs and 16.15% for SSs). Significant variation of Mn distribution patterns between NSCSs and SSs was observed with Mn in NSCSs mainly present in Mn-oxides phase (48.27%) and that in SSs present as residual phase (45.44%). Zn, Cu, Pb and Cd were found dominantly in residual fractions (>48%), and next in solid oxides/hydroxides for Zn, Pb and Cd and in easily oxidizable solids/compounds form for Cu, respectively. The heavy metal distribution pattern implied that Fe/Mn oxides both in NSCSs and SSs were more important sinks for binding and adsorption of Zn, Pb and Cd than organic matter (OM), and inversely, higher affinity of Cu to OM than Fe/Mn oxides in NSCSs and SSs was obtained. Meanwhile, it was found that the distributions of heavy metals in NSCSs and SSs were similar to each other and the pseudo-total concentrations of Zn, Cu, Pb and Cd in NSCSs were greater than those in SSs, highlighting the more importance for NSCSs than SSs in controlling behaviours of heavy metals in aquatic environments.