Thursday, November 26, 2009

Shibi - Yellowfin Tuna or Bigeye Tuna?

Can you tell the difference between a juvenile yellowfin tuna, Thunnus albacares, and a juvenile bigeye tuna, Thunnus obesus?

I've been a fishing enthusiast but for a long time I've had trouble in identifying each of them properly when I took pictures of them. Hawaiian and Japanese fishermen call both juveniles as "shibi", and usually are careless about which. I've been the same way, too.

On the other day, I had an opportunity to compare the two species of similar size. I caught both species on the same day. By comparing them side by side, the difference was obvious.


juvenile yellowfin tunas are called, shibi in Hawaii and Japan, consisting of two differenct species of tunas - yellowfin tuna, Thunnus albacares (above), and bigeye tuna, Thunnus obesus (bottom), note the differences that bigeye tuna has larger eyes, longer pectoral fins and more robust body, Kona, Big Island, Hawaii, USA, Pacific Ocean

The most obvious difference was the pectoral fins. The bigeye tuna has a lot longer pec fin than the yellowfin, passing the dorsal and almost reaching the anal fin. Its body shape is naturally much more robust - looks a lot fatter than the yellowfin does. In addition, the eye of the bigeye tuna was apparently larger relative to the size of the body and head, which explains the origin of the common name of the species.

I always thought the bigeye tuna tastesd better because it looked fatter! Maybe that's not true after all. In any case, they are fabulously good eat. If you are catching one, make sure to take time and bleed them well. It'll make a huge difference at dinner table.

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