they are taken from the rather big trout in my previous picture.

looks more like a steelhead than a "trout"...

Yeah I think you might be right. In the US they would be called steelhead. Although the definition of steelhead seems a bit unclear. From what I understand is that they are searun rainbow trout, that grow larger then normal rainbows and live and spawn like salmon. The rainbow trout that were introduced to New Zealand don't run to sea for some reason. Nobody could figure out why. Only brown trout in New Zealand are sea run. Anyhow even though the rainbows are staying in lakes and rivers, they reach impressive size and look and taste more like steelhead. There must be a difference though. I caught two big rainbow trout in the same lake. They looked similar when I caught them but one had super red meat, was very fatty and tasted almost like salmon. While the other one had pretty pale meat and tasted different.