According to an investigation by the D.C.-based International Consortium of Investigative Journalists, much of the blame lies with the black market, widespread fraud, and a lack of official oversight. You can read more of ICIJ’s Looting the Seas investigation here. There is also a companion documentary, recently aired on BBC World News, which you can order here.
Why should you care about the collapse of bluefin stocks? Consider what the ICIJ wrote:
Biologists warn that at stake is more than the mere loss of a favorite source of sushi. Bluefin tuna, they say, are near the top of the food chain and their demise will have dire consequences for marine ecosystems. Without large predators, entire food chains may erode, leaving the seas overrun by millions of jelly fish and micro-organisms.