I have done the same (thrown guts in bushes), though I admit to not being sure of the legalities of it. It's the same thing we'd do with bunny guts when rabbit hunting, but you had to hang those high so the dogs didn't get em. Statute of limitations has expired, so... I haven't kept a fish in a while.
Back when I did keep some stockies, I used a stringer, however, I killed the fish first. The stringer was an easy way to keep the fish in the water, and hence, cold, as I didn't carry ice with me. Typically I'd only keep 1 or 2, and then maybe a 3rd if you happen to have one take it deep or something. Saved the gutting part for the end of the day and did them all at once.
As it is, I won't kill a normal stocked trout. Simply don't like the taste. Wild fish taste much better. Pink meat, like a salmon, but not quite that strong. I'll admit years ago I killed some wild brookies while backwoods camping on several occasions. I would do so again as well if in that situation. Generally that's a situation where you're C&Ring all day long, but at the end of the day, you keep one or two for the fire. Your gonna cook right away, so while gutting, I'd cut off the head and tail and fins, split it in half down the back, lift out the backbone and hope some bones comes with it, put some butter and Italian seasoning inside, put it back together like a sandwich, wrap in foil, and lay it right on the coals. Turn it once or twice while cooking.
I also have been known to keep a single steelhead on occasion. Usually it's one of those deals where your only gonna keep one if you happen to catch one right at the end of the day anyway. Too cold to gut, too heavy to carry around, lol! Kill it, walk to car immediately, throw it in a plastic bag, drive straight to Poor Richards, trade for a smoked one, drive home.