Comparison of fish communities between above‐ and below‐dam sections of small streams; barrier effect to diadromous fishes

Abstract

To analyse the effects of small-scale dams on fish communities, species diversity, population density, biomass, migration over dams and trophic relationships were investigated in the aboveand below-dam sections of three Japanese streams. The dams were 1Á5-3Á9 m high, constructed within 400 m of the sea, and had no impoundment or fishway. Fish communities were mainly composed of diadromous fishes. Of the 17 species sampled, only a few species of gobies, Rhinogobius spp. and Gymnogobius spp. were able to climb and migrate upstream over the dams. Consequently the number of species, and total density and biomass of fishes below the dams was high, but low above the dams. One of the most dominant fish below dams, Plecoglossus altivelis altivelis, predominantly fed on benthic algae, whereas other fishes preyed on benthic invertebrates. Trophic relationships above dams were very simple, the few species of gobies preying on chironomid larvae and other aquatic invertebrates.

There and back again: migration in freshwater fishes

“…Although migrant fish should be adapted to the varying conditions between environments along the migration route, combinations of habitat changes may restrict the probability of successful migration. Also, if the migration route includes several habitat types, the deterioration of any of these may have impacts on migratory populations and communities (Katano et al 2006). Many freshwater fish migrate along streams and rivers and anthropogenic activities such as damming, irrigation, and dredging affect hydrological, biological, and habitat prerequisites for migration (e.g., Lucas and Baras 2001;Thorstad et al 2008).…”

The effects of the Three Gorges Dam’s (TGD’s) experimental impoundment on the phytoplankton community in the Xiangxi River, China

“…Bi et al migration routes. Among these effects, habitat fragmentation is an obvious consequence of the damming of freshwater ecosystems [11][12][13][14].…”

Effects of a surface oriented travelling screen and water abstraction practices on downstream migrating salmonidae smolts in a lowland stream

“…Dam building and its associated impoundment of rivers and streams have occurred globally for many years (Jungwirth, 1996;Gehrke et al, 2002;Merona et al, 2005;Katano et al, 2006;Sheer and Steel, 2006). The migration performed by potamodromous and diadromous fishes may be delayed or inhibited by dams and weirs (Lucas and Frear, 1997;Gehrke et al, 2002;Sheer and Steel, 2006).…”