I think if we knew how much crab, turbot, cod or other valuable commercial species that seals were eating, we could develop an approach. It may be like pushing a piano upstairs or it may be that we will take an effective management strategy that includes the elimination, where possible, of an adequate number of the top predators.
The next challenge is to make sure that we effectively use what we remove from the ecosystem to the extent possible. However, we cannot not do step two because we can't accomplish step one.