Seals are opportunistic predators, so they eat a lot of other species. By our estimates, crab and lobster are not seals' main prey.
Again, there is a lot of uncertainty in this type of analysis. It must be noted that a number of other predators have seen their populations rise over the same period, including tuna and gannets.
If you would like more information, I can ask my colleague Mr. Hammill to provide it.