PT  - JOURNAL ARTICLE
AU  - Jérôme G. Prunier
AU  - Géraldine Loot
AU  - Charlotte Veyssiere
AU  - Nicolas Poulet
AU  - Simon Blanchet
TI  - Barrier mitigation measures trigger the rapid recovery of genetic connectivity in five freshwater fish species
AID  - 10.1101/2021.12.05.471259
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.12.05.471259
4099  - http://biorxiv.org/content/early/2021/12/06/2021.12.05.471259.short
4100  - http://biorxiv.org/content/early/2021/12/06/2021.12.05.471259.full
AB  - Rivers are heavily fragmented by man-made instream barriers such as dams and weirs. This hyper-fragmentation is a major threat to freshwater biodiversity and restoration policies are now adopted worldwide to mitigate these impacts. However, there is surprisingly little feedback on the efficiency of barrier mitigation measures in restoring riverine connectivity, notably for non-migratory fish species. Here, we implemented a “before-after genetic monitoring” of the restoration of 11 weirs in France using a dedicated genetic index of fragmentation (the FINDEX), with a focus on five fish species from two genera. We found that most obstacles actually had a significant impact on connectivity before restoration, especially the highest and steepest ones, with an overall barrier effect of about 51% of the maximal theoretical impact. Most importantly, we demonstrated for the first time that mitigation measures such as dam removal or fish pass creation significantly and rapidly improved connectivity, with –for some barriers-a complete recovery of the genetic connectivity in less than twelve months. Our study provides a unique and strong proof-of-concept that barrier removal is an efficient strategy to restore riverine connectivity and that molecular tools can provide accurate measures of restoration efficiency within a few months.Competing Interest StatementThe authors have declared no competing interest.