Oxford Modern English Grammar (OMEG) by Bas Aarts has these passages on page 52:
Sentence (40) is apparently taken from an Independent article "How Tuna Conquered the World". Two prior paragraphs along with Sentence (40) are shown here:
Some populations, such as leatherback turtles, are being heavily damaged; pushed to the brink of extinction, even though they are not being hunted. Purse seine boats that drop giant drawstring nets in tuna areas, and "long-liners" which sink lines of up to 80km, hooked with bait, are the biggest by-catch culprits.
Conservationists say pole and line fishing, where boats drops bait into the sea and fishermen claw the tuna into the boat (avoiding other species), are "cleaner" methods.
In a report from Greenpeace last year, and still available online, retailers and canning companies were ranked in order of their tuna-fishing policies. Sainsbury, Co-op and Marks & Spencer came top; Princes and John West – most of whose was from purse seiners – came bottom.
Sentence (40) from OMEG is the same as the last paragraph shown above.
Is this "independent" use of whose grammatical? If so, is it natural English or should tuna be added after whose as follows to make it more natural?
In a report from Greenpeace last year, and still available online, retailers and canning companies were ranked in order of their tuna-fishing policies. Sainsbury, Co-op and Marks & Spencer came top; Princes and John West – most of whose tuna was from purse seiners – came bottom.