Who's to Blame

Sand Eel populations have plummeted in the North Sea. There are two likely culprits:

1. Scientists say that climate change appears to be the cause of their decline.
2. It has also been the basis of the "industrial" fishery in the North Sea which took about 750 million tons of sand eels each year and pulped them for oil and meal used in salmon farms.

Judging by the other problems faced by the fisheries, I'd guess that the common fisheries policy is to blame. Even if climate change is a significant factor, that still means that the CFP allowed continued overfishing at a time when stocks should have been more carefully controlled.