Stream‐dwelling Dolly Varden (Salvelinus malma) density and habitat characteristics in stream sections installed with low‐head dams in the Shiretoko Peninsula, Hokkaido, Japan

Abstract

Numerous low-head dams have been constructed for erosion control and installed in almost all mountainous streams in Japan. Shiretoko Peninsula, Hokkaido, is considered as one of the most intact areas in Japan, however, more than 331 low-head dams have been installed in 39 streams of the peninsula since the 1960s. In this study, the density of stream-dwelling Dolly Varden (Salvelinus malma) and the habitat characteristics in dam-installed sections were investigated in Shiretoko streams and compared with unaltered sections in which no dams have been installed as a reference. Fish density in dam-installed sections was significantly lower than reference sections. Canopy cover, maximum temperature, wetted width, frequencies of pebble, bedrock and boulder, and areas of rapid, glide and riffle was significantly differed between dam-installed and reference sections. High stream temperature, occurrence of glides, and loss of boulder in dam-installed sections may reduce the suitability of habitats for fish and minimize the population size. We suggest that negative effects of dam installations on Dolly Varden populations have occurred in Shiretoko streams.

Distribution of brown trout (Salmo truttaLinnaeus, 1758) (Teleostei: Salmonidae) in its southwesternmost European limit: possible causes

“…Kingsford 2000;Alonso-González et al 2008), alter the dynamics of the whole catchment basin and the periodic patterns of temperature, sediment grain size and composition of the rivers (e.g. Shieh et al 2007;Maddock et al 2008;Kishi & Maekawa 2009) and promote the invasion of exotic species (Clavero et al 2004;Johnson et al 2008), modifying their structure and the natural dynamics of the biota (Bunn & Arthington 2002). Thus, damming is a cataclysmic event in the life of a riverine system (Ligon et al 1995).…”

“…Hart & Poff 2002), with more than twice as many studies being conducted on salmonids than on any other fish family (Murchie et al 2008). Alteration of natural flow regimes modifies the natural rates of growth, development, habitat use, reproduction or size (Yrjänä et al 2002;Kishi & Maekawa 2009) and the construction of hydrological barriers fragments populations into discrete units regardless of historical connections, and causes genetic isolation (Rieman & Dunham 2000;Gosset et al 2006;Heggenes & Røed 2006). To these general effects we have to join the high natural stochasticity of the Mediterranean systems, due to the highly unpredictable interannual flow variations associated with natural seasonal events (Gortázar et al 2007).…”

Controls for trout and char migratory/resident behaviour mainly in stream systems above and below waterfalls/barriers: a multidecadal and broad geographical review

“…(2008) examined by Sn:Ca ratio analysis, variation in migratory history of a Hokkaido population of Dolly Varden having a stream artificial dam, with those above the dam having consistently low ratios whereas many below the dam had higher ratios. Kishi & Maekawa (2009) noted the population density and habitat features of stream sections with low‐head dams in the Shiretoho Peninsula of Hokkaido, Japan, and compared these with unaltered reference sections. Canopy cover, maximum temperature, wetted width, pebble frequencies, bedrock and boulder substrate, and areas of rapids, glides and riffles differed significantly between dam‐installed and reference sections, minimising Dolly Varden populations for dam‐installed stream sections.…”

Strategies for the conservation and management of isolated salmonid populations: lessons from Japanese streams

“…Such barriers can result in the fragmentation of riverine systems and dramatic changes in the physical environment (e.g. temperature and flow regimes, and gravel composition; Kishi & Maekawa, 2009). Research on stream‐dwelling salmonids suggests that the size of isolated habitats is a significant determinant of the persistence of local populations (Rieman & McIntyre, 1995; Harig & Fausch, 2002; Morita & Yamamoto, 2002).…”