The claim is that krill are harvested from more pristine Antarctic waters , so are free of many of the pollutants in waters closer to more populated land masses . Many years ago I saw a slide presentation by a work colleague who was from Newfoundland , the Easternmost part of Canada , of a trip back to his native Province . The Grand Banks off Newfoundland are where much of the cod is harvested . One of his slides was of a bucket at a fishing port where they would toss the livers of the cod when cleaning the fish . He said that every couple of weeks someone would come for the contents of the (unrefrigerated) cod liver bucket and that was the source of medicinal cod liver oil . I lost my taste for cod liver oil after seeing that slide.
One of the claims for Krill oil is that there are no cod liver burps after taking it , and I can attest to the truth of that claim , having been a consumer in the past . Another claim which I cannot personally verify , is that the bio-availability of beneficial Omega’s is greater with Krill oil .
Caveat emptor .
P.S. While I was composing the above , Maya made a more concise reply . I agree with his response .