Fish texture

I was wondering what’s with this “loose” or falling apart texture with this sashimi? Both the salmon and the tuna were like this, like each section of fish was falling apart, and very soft.

I’d love to know what the deal is, is it low quality fish?

Our local spot used to be amazing, but the texture and the darkened edge of these pieces (among other things) have really turned me off.
(The white things are shredded daikon!)