The significance of meandering channel to habitat diversity and fish assemblage: a case study in the Shibetsu River, northern Japan

Abstract

This study examined the structure and function of habitats for fish, the contribution to fish populations, and the effects of channel modification on habitats and fish populations in the lowland meandering Shibetsu River, northern Japan. Electrofishing and environmental measurements were conducted in bank areas of habitats constituting natural meandering and modified reaches. All types of habitats in a meandering reach highly contributed to the fish population(s). In particular, the contributions of lateral and wood habitats to fish populations were generally high, despite the low spatial extent of these habitats. The modified reach was simplified and had fewer types of habitats with uniform currents, and there was a low abundance of most fish within these habitats. Abundance of each fish group (taxa) was negatively affected by the changes to the habitats and/or channel shortening (i.e., decrease in the absolute abundance of habitat) due to river modification, which was implemented during 1950-1978. This study suggests that the recovery of all the habitat types is important in meander restoration and that the changes in habitat types and abundance should be examined in monitoring meander restoration and channel shortening.

River habitat homogenisation enhances trophic competition and promotes individual specialisation among young of the year fish

“…Pinder, & Leach, 1997;Pinder, 2001). Habitat diversity afforded by lateral connections and low mainstream regulation could improve fish recruitment by offering nursery habitat for a larger number of species, and potentially a wider diversity of food sources (Keckeis, Winkler, Flore, Reckendorfer, & Schiemer, 1997;Konrad et al, 2016;Nagayama & Nakamura, 2018;Reckendorder et al, 2001;Schiemer, Spindler, Wintersberger, Schneider, & Chovanec, 1991). In the Great Ouse River, the recruitment of numerous species decreased and many cyprinid fish became locally extinct due to the river regulation and habitat homogenisation (Copp, 1997).…”

“…This may be related to the later reproduction of other fish species as tench Tinca tinca , common carp Cyprinus carpio, minnow Phoxinus phoxinus, barbel Barbus barbus , or common bream Abramis brama , which compensated mortality of the early spawning species as roach and chub (Bass, Pinder, & Leach, ; Pinder, ). Habitat diversity afforded by lateral connections and low mainstream regulation could improve fish recruitment by offering nursery habitat for a larger number of species, and potentially a wider diversity of food sources (Keckeis, Winkler, Flore, Reckendorfer, & Schiemer, ; Konrad et al., ; Nagayama & Nakamura, ; Reckendorder et al., ; Schiemer, Spindler, Wintersberger, Schneider, & Chovanec, ). In the Great Ouse River, the recruitment of numerous species decreased and many cyprinid fish became locally extinct due to the river regulation and habitat homogenisation (Copp, ).…”

Spatiotemporal Distribution and Species Composition of Fish Assemblages in the Transitional Zone of the Three Gorges Reservoir, China

“…Variations in the spatiotemporal distribution of fish can be attributed to abiotic, biotic, and anthropogenic factors such as water temperature, water depth, channel morphology, substrate composition, flow velocity, and dam impoundment [38][39][40][41]. There are several factors that may explain this fish distribution in the Mudong reach.…”

“…Such diverse bathymetric features produce habitat heterogeneity with high hydrological variability and diversity in substrate types, such as a lateral gradient of depth from shallow to deep areas and repeated structures of pools and riffles, where the sedimentation of suspended particles, including drifting forage organisms, takes place [42]. Field studies and river restoration case studies have shown that a large variety of habitat conditions and sufficient food provisions at such areas support high diversity and abundance of aquatic organisms such as fish and macroinvertebrates [40,42]. Conversely, a number of fish do not prefer to reside in the straight reach with the simple structure and high flow velocity [40].…”

“…Field studies and river restoration case studies have shown that a large variety of habitat conditions and sufficient food provisions at such areas support high diversity and abundance of aquatic organisms such as fish and macroinvertebrates [40,42]. Conversely, a number of fish do not prefer to reside in the straight reach with the simple structure and high flow velocity [40]. Accordingly, in the present study, the fish densities were considerably higher in Sections 1, 3 and 4, which had strongly meandering channel morphologies, than in the relatively strait sections.…”