Re: Or you could consider a simpler explanation, TRADE
I also didn't see much analysis of the option that the well-developed shark-fishing techniques in the 1800's may have caught the odd rare dusky which had strayed well outside its normal habitat.
Considering the complete lack of evidence for the quantity of "extinct" sharks in the sea around the islands and the complete lack of evidence of fishing technique for/impact on different species, the leap to "we killed them all with industrial activities" seems a little premature. Trendy, perhaps even likely, but premature. I note that overfishing in the 1800's by the islanders doesn't appear to be considered as an option.
While the original article was more circumspect than el reg's version, there was still far too much certainty of interpretation given the very large holes in what is known.
Unfortunately, this appears to be a common problem in what is often labelled "science." It is certainly research, but it would be generous to even call it "forensic science." It is a survey with some educated-guesswork.
Don't get me wrong, I'm no fan of industrial-scale fish-harvesting, but I don't think the conservation cause is helped by shouting about overly-simplistic and thinly-evidenced studies.
"It ain't what you don't know what gets you into trouble, its what you know for sure that ain't so."