Tuna

Tuna is a type of fish which is native to Earth, It is blue to silvery color and is very strong and big. It is used by humans as a food source. Tuna is apparently considered to be a great luxury, the very fact of it being on a menu at all being worthy of comment. It is available at some human food outlets, including the restaurant at the Waterfront Hotel in New York City. You might see Tuna on Sierra 117 after Johnson's pelican goes down, you can jump into the water and look around for them. This is odd because Tuna are native to the Atlantic Ocean, while Kenya, where the Earth levels of Halo 3 take place, borders the Indian Ocean, on the entire different side of the continent from where Tuna would be found.