The ones you caught are Blue Salmon (Most common name) but also called Blue Threadfin. Eleutheronema tetradactylum.
They go like the clappers, but don't grow as big as "King" Salmon. I have heard of some getting up to the metre mark, but the biggest I've seen are in the high 70's cm.
Eating wise, I recon they aren't as good as King Salmon, but still pretty good. Quite soft flesh.