These are another of those fish that look quite different when they catch the light, with blue highlights standing out. They also look different as they age. The top photo is a large adult, the other two, a small younger adult.
These fish are big time predators, eating many other species of fish. I find this interesting because I often see bluefin trevally when I’m in the water. I see them pass by other fish and I’ve never seen them strike or seen other fish particularly bothered by their presence. One day …
In my attempts to identify what I see in the water, I use John P. Hoover’s book The Ultimate Guide to Hawaiian Reef Fishes, Sea Turtles, Dolphins, Whales, and Seals. His website is hawaiisfishes.com.