[zan]

I don't know about the evidence for the UK, but in the Grand Banks they believe that the cod may not be recovering because of the predation from seals. After the cod stocks crashed, it is believed that they may now be at such a low level that the seals are preventing them from recovering. So we caused the crash, but now it's happened it's the mammals that *might* be keeping them down.

The problem with a lot of these theories is that ecosystems are so complex it's virtually impossible to say what the effects of removing \ adding another species will be until it's done. I'd be very wary of this kind of approach, particularly given the bias towards whaling in Japan anyway.