Conservation genetics of riverine salmonids in the Southern Alps: a synthesis.

Riverine salmonids (trouts and grayling) represent important flagship species of Southern Alpine freshwater fish fauna, to date seriously endangered by various anthropogenic pressures. Among these, genetic pollution, fuelled by stocking of non-native conspecifics, is recognised as a primary stressor. Hybridisation, introgression and, finally, the loss of native taxa are potential consequences of these improper fisheries management actions. Here, we summarise the results of recent broadscale conservation studies focussing on marble trout (N=1,246), brown trout (N=467) and European grayling (N=683) and based upon multilocus-genetic (mtDNA sequencing and micosatellite genotyping) as well as fisheries data. We outline species-specific responses in terms of secondary contact between native and foreign taxa. Following an altitudinal gradient, we point to the almost complete absence of Adriatic brown trout and widespread expansion of hatchery-derived Atlantic brown trout in high-alpine brooks. Downstream, we compare differential patterns and extents of hybridisation and genetic introgression in both marble trout and Adriatic grayling populations. While exotic genetic profiles were mono- specific (Atlantic) in marble trout hybrids, multiple exotic source populations were identified in introgressed grayling, reflecting differences in stocking histories of trout and grayling. So forth, we propose management units, fundamental to conserve the residual genetic legacy of indigenous salmonids in the Southern Alps. Finally, we press for updated fisheries management actions. This revised management catalogue includes changes in stocking practices, fisheries regulations as well as the routine adoption of genetic assistance in supplementation programs