I did take some trout to eat on my last day of fishing. At Henry's Fork

I opened up their guts, and they were primarily full of aquatic plants.

Do they eat plants for nutrition, or are they just eating them by accident as they float by thinking they are something more nutritious like a fly or larva?

My guess is they were eating scuds out of the weeds... But will defer to flyfisher87 for the answer.

Probably picking inverts off them. Wha kind of trout was it? Lake, brook, bows, cuts?

Rainbows

Most likely they were picking up the plant matter along with inverts.

Alot of the water up in Colorado has "fresh water shrimp" in it. When I was a kid fishing up there you'd encounter the same issue. But, if you looked closely you'd find the shrimp.
One other thing that was really cool was that the meat on fish that had a high percentage of shrimp in their diet was bright orange ( like a normal Brook Trout/Char). At least that's what the oldtimers alluded to.

Very similar to when we dissected the crop of our sharptails in Montana a couple of years ago. We found a ton of alfalfa in their crops. The birds were hunting grasshoppers. The hoppers were in the green alfalfa and the birds were getting lots of greenage in addition to the grasshoppers.

just came across this pic on FB for a rod maker manufacturer. This pic is for Sean.

New Zealand or Argentina Shifty?

Chile

My next guess, darnit!

OMG is that Chilean Sea Bass?

That fish is as large as 2 men, so it MUST way 350 pounds. That has to be a record or something.

Nice exaggerative picture of a 28" fish.

Unless the guide has really short arms...