Effect of habitat fragmentation on spawning migration of brown trout (Salmo truttaL.)

Abstract

Gosset C, Rives J, Labonne J. Effect of habitat fragmentation on spawning migration of brown trout (Salmo trutta L.).Abstract -Human-induced habitat alteration is one of the main causes of the decline of freshwater fish populations. The watershed of the River Bidasoa (Spain) is an example of heavily fragmented habitat. The local brown trout (Salmo trutta L.) population is disturbed, with evidence of poor recruitment as well as low adult densities in the main stem. Forty male and female adult migratory trout were tagged with external or internal radio transmitters and released. Fixed stations with data loggers and mobile antennae were used with daily surveys to track fish movements during the migration and spawning period (3 months). Migration distances did not exceed 10 km, and half of the fish never entered a tributary in the study area. Fragmentation because of weirs on the main stem apparently prevented fish from reaching their spawning destination. Fish that entered the tributaries were first confronted with an accessibility problem because of low discharge. However, each fish chose one tributary, without making attempts to run up in other tributaries. Once in the tributary, fish were restrained in their upstream movements by dams. The study area appeared to be isolated from the vast upper part of the watershed. Within the study area, upper parts of tributaries also seemed strongly disconnected from the main stem. This study illustrates the negative impact of river fragmentation on S. trutta migration pattern. Population sustainability can be directly affected through the low availability of spawning grounds for migratory fish. Long-term effects of fragmentation may cause reproductive isolation within watersheds, which in the case of trout also means isolated phenotypic population units.

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

“…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). Dams often reduce access to spawning (Agostinho et al, 2002;Gosset et al, 2006), nursery (Saunders, 1960;Arnekleiv and Rønning, 2004) and foraging (Aarestrup and Koed, 2003) areas potentially leading to fragmentation effects on the genetic structure (Meldgaard et al, 2003;Heggenes and Røed, 2006) and even genetically depauperate fish populations (Hansen and Jensen, 2005).…”

Linking individual behaviour and migration success inSalmo salarsmolts approaching a water withdrawal site: implications for management

“…In potamodromous and diadromous fishes, dams and weirs often delay or inhibit access to spawning (Gehrke et al 2002;Gosset et al 2006), nursery (Saunders 1960;Arnekleiv and Rønning 2004) and foraging (Agostinho et al 2002;Aarestrup and Koed 2003) areas. Impeded migration may lead to fragmentation effects on the genetic structure (Meldgaard et al 2003;Heggenes and Røed 2006) and even genetically depauperate fish populations (Hansen and Jensen 2005).…”

Influences of habitat fragmentation by damming on the genetic structure of masu salmon populations in Hokkaido, Japan

“…Indeed, dam construction could prevent fish movement, causing the depopulation or extirpation of salmonid habitats (Burdick and Hightower 2006;Gosset et al 2006;Fukushima et al 2007). Moreover, negative impacts on genetic structuring, such as an increase in genetic differentiation and loss of genetic diversity, have been reported for several salmonid species (e.g., Meldgaard et al 2003;Wofford et al 2005).…”

“…Dams prevent fish migration throughout a river system, particularly upstream migration, isolating upstream populations (Gehrke et al 2002;Gosset et al 2006). Such blockages reduce population size, alter life history features, and shift the spatial population structure and/or their genetic components (Morita and Suzuki 1999;Heggenes and Roed 2006;Fukushima et al 2007).…”