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.     

Humic Acid Interferes with Species Recognition in Zebrafish (<Emphasis Type="Italic">Danio rerio</Emphasis>)

Few studies have addressed how chemosensation may be impaired by chemical alterations of the environment and anthropogenic disturbance. Humic acid (HA) is a pervasive, naturally occurring organic derivative found in aquatic and terrestrial environments; human activity, however, can lead to elevated levels of HA. Recent studies suggest that environments that contain high levels of HA may hinder chemical communication. We tested the ability of adult zebrafish (Danio rerio) to discriminate between conspecific and heterospecific urinary chemical cues found in the presence and absence of HA. We show that high humic acid levels (200 mg/l) can impair the ability to differentiate conspecifics from heterospecifics. We also found that zebrafish prefer untreated water over HA-treated water. These findings suggest that, in addition to human-produced synthetic compounds, changes in the abundance of naturally occurring substances may also negatively impact natural behaviors in aquatic species by disturbing the sensory environment.     

Attraction of female fathead minnows,Pimephales promelas,to chemical stimuli from breeding males

Female fathead minnows,Pimephales promelas, were attracted to water that had contained conspecific males in breeding condition. The attraction was particularly strong in the morning and occurred in both females with mature gonads and gonadally regressed females. Females were also attracted to water that had contained other females but this attraction was weaker than the attraction to breeding males and tended to occur in afternoon trials. When offered a choice, females preferred breeding male water over regressed male water or female water. Swarming behavior, in which females formed a very active group near the water inlet, occurred primarily in test locations receiving water from breeding males. Our results indicate that breeding maleP. promelas produce water-borne chemical stimuli that attract females and that females distinguish breeding male stimuli from female or regressed-male waterborne stimuli.     

First Records of Rhinogobius lindbergi (Teleostei: Gobiidae) and Abbottina rivularis (Teleostei: Cyprinidae) in the Lake Buyr Drainage,Mongolia

We report the first records of Amur goby, Rhinogobius lindbergi and the Chinese false gudgeon, Abbottina rivularis from the Lake Buyr drainage of eastern Mongolia. Both species were previously known only from much farther downstream in the Amur River basin. Because of their abundance at three sites separated by 11 km in Lake Buyr and a tribuary stream, and presence of multiple size classes, we strongly suspect that these species are established. Both species have been widely dispersed outside of the Amur River basin as contaminants in cultured, large-bodied cyprinids (Ctenopharyngodon, Hypophthalmichthys, Parabramis), and we suggest that this is the most likely means of their introduction into Lake Buyr. The long-term impacts of these species on the native ichthyofauna are unknown, but unlikely to be positive. We suggest that immediate measures be taken to monitor their dispersal, and to prevent similar introductions in the future.     

An isozyme analysis of four species in the family Cyprinidae: genetic,taxonomic and germplasm significance

The tissue distribution of products of 35 enzymatic loci (19 enzyme systems and soluble protein) was examined with different buffer systems and gel thicknesses to identify optimal polyacrylamide gel electrophoretic conditions for allozymic and isozymic studies of the black carp (Mylopharyngodon picius), grass carp (Ctenopharyngodon idellus), silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichys nobilis). Relative levels of enzyme activity are reported for extracts prepared from brain, eye, heart, kidney, liver and muscle. The results showed that the difference within species tissues was greater than that among species; the results showed that the differences of activity between tissues within species was greater than among species; however Acp, Adh, Amy, Cat, Est, Ichh, Gtdh, Mdhp, Pox, Iddh and SP activities present differences among the four species and could be used as genetic markers of species. The electrophoretogram characteristics of Cox, Ldh and G6pdh can be employed as the markers for distinguishing the Leuciscinae and Hypophthalmichthyinae. Copyright © 2005 Society of Chemical Industry