Does anyone know how2tell the difference between a bigeye tuna&a yellowfin tunasomething to do w/their liver?

Answer 1

The best-accepted method of distinguishing a bigeye from a yellowfin is by examining the whole liver, which is different from a liver biopsy (a technique of examining the cells microscopically). When viewed from the bottom, the three lobes of the bigeye tuna's liver are about the same size, and the surface is streaked with lines. The yellowfin has a long lobe at one end of the liver and a short lobe at the other, and the surface of the liver is smooth.
Regarding the long second-dorsal and anal fins, not all yellowfin have the typical, very extended "yellowfin fins." While some adults have very long fins, others' fins are hardly elongated at all. In any case, the fins of small, juvenile yellowfin aren't any longer than the fins of juvenile bigeye. On an average, the yellowfin's fins don't grow noticeably longer until they reach about 60 pounds.
When it comes right down to it, it's hard to tell yellowfin and bigeye apart. Some field samplers say they see a difference in the overall proportions of the fish: The pectoral fin of the yellowfin is slightly longer than that of the bigeye; there's a gold stripe on the flank of a live yellowfin that's not there on a live bigeye; or there's a distinctive difference in the shapes of the notches in the center of the fishes' tails - but none of these criteria is foolproof.

Answer 2

The Yellowfin Tuna has

Yellowfin tuna – There was an international agreement brokered by ICCAT in 1975 that established a minimum size limit for this species of 3.2 kilograms. At present, compliance with this regulation has been non-existent by all signatories with the exception of the United States and Canada. It is currently estimated that in excess of 50% of the Atlantic catch is made up of fish under this minimum size limit. It is incumbent upon the United States delegation to take a leadership role in assuring this compliance issue is addressed and corrected.

Bigeye Tuna – More recently, ICCAT reaffirmed that the same 3.2 minimum size applied to bigeye tuna, yet it is estimated that in excess of 70% of the harvest of Atlantic bigeye tuna is under the minimum size limit. All nations must comply with this most basic of conservation measures if any of the goals of stock protection are to be achieved.

Answer 3

Best way is to look at the dorsal fin. The Yellowfin tuna has a longer top fin than a Big Eye. If you cutting open the tuna, you could tell by the serrated liver. I think it's the Yellowfin that has a serrated liver while the Big Eye's liver is smooth.

Answer 4

http://www.swordfishingcentral.com/albums/Tuna/tuna_001.jpg
http://aboardfishing.com/fishing/yellowfin-lrg.jpg
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