 Around April, harvest begins and fish are gently guided into a boat (any bruising lowers the price) where they are killed, flash frozen and most placed on Tokyo-bound planes.Armed guards are paid to watch over them as 2,000 tuna kept in a single pen are worth around $2 million.Australia exports 10,000 metric tons of southern bluefin tuna worth $200 million; almost all is from ranched stocks.