One of the most unique things we did while on Oahu was attend a fish auction at the United Fishing Agency. This auction goes on M-Sat., occurs pretty early in the morning, and is the main source of all the local fresh seafood that winds up on your plate in the evening.
Buyers from all types of restaurants, stores, and even wholesalers attend the auction and bid on a great variety of fish. The auction continues until all the fish are sold. It's amazing to see the prices some of the tuna were fetching.
Among the species we saw were tuna, swordfish, hapupu, sunfish, and many more.
It's a little bit smelly and wet, but hey its a fish auction!
United Fishing Agency, 117 Ahui St. (below John Dominis Restaurant), Honolulu, HI
The only thing I could find on the web was from Frommers, but it has the same information. Also, the fish market in Hilo has been closed so this is the only one to see.