Dogbreath your saying that no matter how long it takes to land the fish they are always edible? I found this
The Australian government alleged in 2006 that Japan had illegally overfished southern bluefin by taking 12,000 to 20,000 tonnes per year instead of the their agreed 6,000 tonnes; the value of such overfishing would be as much as USD $2 billion. Such overfishing has severely damaged bluefin stocks. According to the WWF, "Japan's huge appetite for tuna will take the most sought-after stocks to the brink of commercial extinction unless fisheries agree on more rigid quotas". Japan's Fisheries Research Agency counters that Australian and New Zealand tuna fishing companies under-report their total catches of southern bluefin tuna and ignore internationally mandated total allowable catch totals
That sure does seem to contradict your 2nd statement. should I really keep looking?
as for your 3rd statement the fish in question is indeed going in the trash as it's being stuffed rather than eaten, the article even states that.
OK, after going and READING, the southern bluefin is very much overfished and in decline, it is amazing that you would post what you did like some authority on the subject even stating "There are lots of Southern Bluefin Google is your friend in that regard." YES you know what GOOGLE IS YOUR FREIND! you should try it!
"Australian catch peaked in 1982 at 21,500 tonnes, and the total population of SBT has since declined by about 92 percent."