Prediction of size-dependent risk of salmon smolt (Salmo salar) escape through fish farm nets

•The size of smolt needed to avoid escape risk differs with mesh state and openness.•The smolt size required becomes twice as large for slack than for stiff meshes.•For semi-slack meshes, an openness of 80 % implies the highest risk of smolt escape.•More exposed fish farms can imply higher risk for escape through net meshes.