Breakdown of the brown trout evolutionary history due to hybridization between native and cultivated fish

Abstract

Genetic changes in the population structure of brown trout Salmo trutta in the eastern Pyrenees were monitored during the 1990s. Stocking with cultivated exogenous fish has resulted in introgressed populations where those with higher introgression coefficients also have the highest values of heterozygosity. Nevertheless, this increase of local diversity reflects a decrease of genetic differentiation between populations and loss of native alleles. These changes obscure native gene pools and modify evolutionary distinctions among native brown trout populations. # 2004 The Fisheries Society of the British Isles

Genetic risks of supplementing trout populations with native stocks: a simulation case study from current Pyrenean populations

“…The 297 supplementation effort was adjusted to accept the one-migrant-per-generation (OMPG) 298 rule, considered enough to maintain polymorphism and heterozygosity levels within 299 wild locations, while facilitating divergence (Mills and Allendorf 1996). This level of 300 hatchery introgression per generation was consistent with previous estimates in the 301 study area resulting from release of foreign hatchery fish (1 to 5%, Araguas et al 2004). …”

Efficiency of markers and methods for detecting hybrids and introgression in stocked populations

“…Fish collected by electroshocking in 1993 and previously analyzed for allozyme variation (Araguas et al 2004) were selected for comparative microsatellite analyses. Legal restrictions on lethal sampling to a maximum of 25 fish per sample and the availability of fish limited numbers of some collections, as typified in many endangered species (Frankham et al 2002).…”

“…A restricted sample length within a 15-20 cm range approximated a common age class of 1-2 years for all fish. Published allozyme data from the Bagà hatchery stock (García-Marín et al 1991;Araguas et al 2004), were included in the analyses to represent the pure hatchery population. These hatchery fish were no longer preserved and a new collection representing random descendents of the earlier one (Bagà Hatchery personnel, personal communication) was obtained for microsatellite analysis.…”

Genetic diversity and population structure of white-spotted charr, Salvelinus leucomaenis, in the Lake Biwa water system inferred from AFLP analysis

“…The extensive stocking of hatchery-reared charr in the last 30 years in the Lake Biwa water system might have led to a gradual homogenization of the natural genetic differences among populations (Kikko et al 2007). This situation is similar to that of the Mediterranean brown trout Salmo trutta (Araguas et al 2004). In order to conserve the genetic diversity of the white-spotted charr in the Lake Biwa water system, it is necessary to ensure that hatchery-reared charr are not stocked in the reaches where hatchery-reared charr have not previously been stocked.…”