| Identification
& Biology: |
The body is deep and typically tuna-shaped. Its back is deep
metallic blue and the lower sides and belly are whitish. This
species closely resembles small and medium yellowfin tuna.
In live specimens, it has a faint iridescent blue band along
the sides rather than the yellowish band of yellowfin tuna.
It is also lacking the vertical bands of dots often found
on the bellies of yellowfin tuna. It definitely has a larger
eye, but this is a difficult feature to depend upon for identification,
unless a yellowfin tuna is present for comparison or the angler
is highly experienced.
Bigeye tuna feed at night as well as in daylight, and often
feed at great depths. A bigeye tuna tagged with a radio transmitter
was observed to dive 822 feet in less than one minute. The
water temperature was 75ºF at the surface and 48ºF
at the 822 feet. That much temperature change in less than
one minute would kill many other fish. Favored foods include
mackerel, other smaller tuna, flying fish, snake mackerel,
pomfret, squid, and larval crabs and shrimp. Bigeye tuna live
to over 10 years of age. Beginning at age 3, they spawn several
times each summer in the open sea. See the entry under Yellowfin
Tuna for more information on tuna biology. |
