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Tuna |
Thune
are several species of ocean-dwelling fish in the family Scombridae
, mostly in the genus Thunnus . Some tuna are able to inhabit
freshwater environs as well. Tunas are fast swimmers,they have been
clocked at 77 km/h (48 mph)and include several species that are
warm-blooded . Unlike most fish species, which have white flesh,
the flesh of tuna is pink to dark red. This is because tuna muscle
tissue contains greater quantities of myoglobin , an oxygen -binding
molecule. Some of the larger tuna species such as the bluefin tuna
can raise their blood temperature above the water temperature with
muscular activity. This enables them to live in cooler waters and
survive a wider range of circumstances. Some tuna species and fisheries
are overfished and there are risks of some tuna fisheries collapsing. |
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2007 Marine Life Limited Partnership |