Ontogenetic selection on hatchery salmon in the wild: natural selection on artificial phenotypes

Captive-bred Atlantic salmon released into the wild have fewer offspring than wild-bred fish and decrease population productivity

The release of captive-bred animals into the wild is commonly practised to restore or supplement wild populations but comes with a suite of ecological and genetic consequences. Vast numbers of hatchery-reared fish are released annually, ostensibly to restore/enhance wild populations or provide greater angling returns. While previous studies have shown that captive-bred fish perform poorly in the wild relative to wild-bred conspecifics, few have measured individual lifetime reproductive success (LRS) and how this affects population productivity. Here, we analyse data on Atlantic salmon from an intensely studied catchment into which varying numbers of captive-bred fish have escaped/been released and potentially bred over several decades. Using a molecular pedigree, we demonstrate that, on average, the LRS of captive-bred individuals was only 36% that of wild-bred individuals. A significant LRS difference remained after excluding individuals that left no surviving offspring, some of which might have simply failed to spawn, consistent with transgenerational effects on offspring survival. The annual productivity of the mixed population (wild-bred plus captive-bred) was lower in years where captive-bred fish comprised a greater fraction of potential spawners. These results bolster previous empirical and theoretical findings that intentional stocking, or non-intentional escapees, threaten, rather than enhance, recipient natural populations.

Prescriptive Evolution to Conserve and Manage Biodiversity

We are witnessing a global, but unplanned, evolutionary experiment with the biodiversity of the planet. Anthropogenic disturbances such as habitat degradation and climate change result in evolutionary mismatch between the environments to which species are adapted and those in which they now exist. The impacts of unmanaged evolution are pervasive, but approaches to address them have received little attention. We review the evolutionary challenges of managing populations in the Anthropocene and introduce the concept of prescriptive evolution, which considers how evolutionary processes may be leveraged to proactively promote wise management. We advocate the planned management of evolutionary processes and explore the advantages of evolutionary interventions to preserve and sustain biodiversity. We show how an evolutionary perspective to conserving biodiversity is fundamental to effective management. Finally, we advocate building frameworks for decision-making, monitoring, and implementation at the boundary between management and evolutionary science to enhance conservation outcomes.