Yellow fin tuna are auctioned at the tuna port in General Santos on Sarangani Bay in southern Mindanao.
The small harbor is so packed with fishing boats that rafts are used to bring the fish from the boats that can not get a berth at the dock.
A tube is inserted into the fish to take a core sample of the meat to determine it's grade. The value of the fish varies greatly influenced by how much the fish was stressed during it's capture and how well the fish was iced down after the catch.
Big money changes hands at this auction and the fish are shipped to Tokyo, Seoul, San Fransisco and other places by air as soon as the auction is over. The lower grade tuna is for local consumption.
Usually it takes an invite by one of the buyers to gain access to the auction because the action is fast and fierce and they don't want a bunch of tourists getting in the way.