I saw someone coming down the trail two weeks ago who was carrying fishing gear. The main trail was closed beyond Lone Pine Lake at that time, so I assume he fished there (unless he did a ninja run and went up to Mirror Lake or higher). I don't know whether he caught anything, though.
There are reports of trout in some of the lakes, though:
"The Department of Fish and Game stocks Lone Pine Lake with rainbow trout, and there are also allegedly brook trout here too. If you’re into fishing and are camping, you can bring a rod with you and fish. I’ve heard to folks landing trout at both Consultation Lake and Mirror Lake. Word has it the fish are biggest at Consultation Lake."
(source:
https://hikingguy.com/hiking-trails/hikes-around-mt-whitney/mt-whitney-hike/)
