How do dams affect freshwater fish distributions in Japan? Statistical analysis of native and nonnative species with various life histories

We examined the effects of dams on freshwater fish species based on data collected during 1990–2004 from 200 drainage systems in Japan. Of the 76 fish species examined, the occurrence of 20 species within Petromyzontidae, Cyprinidae, Cobitididae, Salmonidae, Cottidae, and Gobiidae was negatively affected by the presence of dams located in the downstream reaches of fish survey sites, whereas the occurrence of 12 species within Cyprinidae, Adrianichthyidae, Centrarchidae, and Gobiidae was positively associated with the presence of dams. A significantly higher proportion of the fishes with a negative damming effect were diadromous species as compared to the fishes with a positive damming effect. Conversely, the latter group had a significantly higher proportion of nonnative species than the former. A significant interaction existed between the effects of damming and the effects of elevation on family-specific species richness. Families dominated by native migratory species showed a greater reduction in the number of species above dams at lower elevations, whereas families represented primarily by nonnative species had higher species richness above dams at higher elevations, except for Centrarchidae, which was always higher in species richness above dams regardless of elevation. Based on our findings, dams in Japan have adversely affected native freshwater fishes by blocking their migration routes, favoring nonnative fishes, or altering existing habitats.     

葛洲坝水利枢纽兴建后长江干流铜鱼和圆口铜鱼的繁殖生态

本文报道了葛洲坝水利枢纽兴建后,长江干流铜鱼和圆口铜鱼的产卵场分布、产卵规模、产卵季节以及促使产卵的主要外界条件等。指出葛洲坝水利枢纽截流后,大坝附近江段铜鱼产卵场的变化情况。分析和讨论了大坝对两种铜鱼的影响程度、两种铜鱼产卵与水文条件的关系及其资源的保护等问题。     

三峡大坝截流前后长江中上游江段水化学特性的初步调查

1997-1998年,在三峡大坝截流前后,对长江中上游地区十多个江段及若干个支流进行了多次的水质监测分析。结果表明:长江中上游水资源丰富,但污染较严重。从多项数据指标分析结果和多项资料表明,目前污染源主要为沿江工业和城市生活污水。长江干流污染远高于支流(嘉陵江除外).而大江截流对长江中上游的水质近期影响较小,可以忽略不计。       

Effect of damming on distribution of rainbow trout in Hokkaido,Japan

Rainbow trout introduced into Hokkaido in 1920 have become widely distributed due to extensive release into many reservoirs and lakes for sport-fishing; their presence often results in reductions of native fish populations. We analyzed and predicted the relationship between the probability of occurrence of rainbow trout and the proximity of dams (or attributed reservoirs), using a database of the presence or absence of rainbow trout collected during 1960–2004 in Hokkaido to clarify the spread patterns of exotic species (e.g., rainbow trout) due to large-scale damming over a long period. Rainbow trout were abundant in streams within approximately 10 km of dams in recent years, regardless of whether the stream was up- or down-stream from the dam and after accounting for the effects of other environmental variables (e.g. elevation, population density, and survey year). A delayed increase in trout occurrence below dams as compared with above dams suggests that the occurrence below dams may be largely due to escapement of stocked populations and a continuously increasing abundance since 1970. The management of dams and reservoirs is necessary to prevent further spread of rainbow trout because they can threaten habitats of native Japanese salmonids through various mechanisms.