Stocking activities for the Arctic charr in Lake Geneva: Genetic effects in space and time. Issue 14 (7th June 2017)

• Record Type: Journal Article
• Authors: Savary, Romain; Dufresnes, Christophe; Champigneulle, Alexis; Caudron, Arnaud; Dubey, Sylvain; Perrin, Nicolas; Fumagalli, Luca
• Is Part Of: Ecology and evolution. Volume 7:Issue 14(2017:Aug.)
• Page Start: 5201
• Page End: 5211
• Publication Date: 2017-06-07
• Subjects: conservation‐based stocking programs -- fisheries management -- genetic bottleneck -- genetic integrity -- historical DNA -- microsatellites -- Salmonids -- Salvelinus; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.3073
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: Artificial stocking practices are widely used by resource managers worldwide, in order to sustain fish populations exploited by both recreational and commercial activities, but their benefits are controversial. Former practices involved exotic strains, although current programs rather consider artificial breeding of local fishes (supportive breeding). Understanding the complex genetic effects of these management strategies is an important challenge with economic and conservation implications, especially in the context of population declines. In this study, we focus on the declining Arctic charr ( Salvelinus alpinus ) population from Lake Geneva (Switzerland and France), which has initially been restocked with allochtonous fishes in the early eighties, followed by supportive breeding. In this context, we conducted a genetic survey to document the evolution of the genetic diversity and structure throughout the last 50 years, before and after the initiation of hatchery supplementation, using contemporary and historical samples. We show that the introduction of exotic fishes was associated with a genetic bottleneck in the 1980–1990s, a break of Hardy–Weinberg Equilibrium (HWE), a reduction in genetic diversity, an increase in genetic structure among spawning sites, and a change in their genetic composition. Together with better environmental conditions, three decades of subsequent supportive breeding using local fishes allowed to re‐establish HWE and the initial levels of genetic variation. However, current spawning sites have not fully recovered their original genetic composition and were extensively homogenized across the lake. Our study demonstrates the drastic genetic consequences of different restocking tactics in a comprehensive spatiotemporal framework and suggests that genetic alteration by nonlocal stocking may be partly reversible through supportive breeding. We recommend that conservation‐based programs consider local diversity and implement adequate protocols to limit the genetic homogenization of this Arctic charr population. Abstract : Fish stocking practices are widely used worldwide but their beneficial effects are controversial. In this context, we conducted a multilocus genetic survey of the declining Arctic charr population of Lake Geneva (Switzerland and France), to understand the genetic impact of 30 years of stocking activities, which involved traditional restocking with allochtonous fishes followed by supportive breeding of local ones. We took advantage of historical and contemporary samples to analyze different time points and localities. Our results show profound changes in genetic composition, structure, and diversity following allochtonous releases in the 1980s. The initial diversity was then partially restored with the subsequent supportive breeding program, which, however, promoted strong genetic homogenization throughout the lake. Our study provides an unprecedented spatial and temporal resolution to understand the genetic consequences of the two main stocking strategies implemented in turns and gives applied insights for future management and conservation of exploited fish populations.