Simplify the following text for a Grade 11 native English-speaking person.
Original: In 2010 , Greenpeace International has added the albacore , bigeye tuna , blackfin tuna , pacific bluefin tuna , northern bluefin tuna , southern bluefin tuna and the yellowfin tuna to its seafood red list .
Simplified: Tuna is an important commercial fish . Some varieties of tuna , such as the bluefin and bigeye tuna are threatened by overfishing , dramatically affecting tuna populations in the Atlantic and northwestern Pacific Oceans .