Impact assessment and remediation of anthropogenic interventions on fish populations - (FISHGUARD)

The disruption of longitudinal river connectivity by man-made obstacles and the
stocking of fish communities with non-indigenous species or genotypes threaten the
fish fauna of Belgian rivers to various extents. Obstacles impede migrations between
habitats that are vital for populations, and they may restrict the gene flow between
populations, thereby reducing the effective size and genetic diversity of populations
and increasing the risk of local extinction. Restocking programs often involve the introduction
of non-indigenous genotypes in native populations. Moreover, although
stocking programs lead to the temporal and superficial enrichment of local fish communities
or gene pools, they generally result in a loss of biodiversity on a regional or
international scale through the homogenisation of communities and the breakdown of
genetic differentiation between populations. Thus, stocking programs cannot compensate
for the loss of free migration by artificial obstructions. The impact of these
changes on fish populations remains largely unknown, which complicates the priorisation
of spots to preserve and spots to restore. Here, we present an integrated
study on Belgian waters, both in Flanders and Wallonia, which analyses fish communities,
gene flow and migration patterns in the field, as well as the swimming and
leaping performances of fishes under controlled conditions.