I always have my camera ready before I take the fish out of the water. When fishing alone I get the camera into position first, with the timer on for 10 seconds, more then enough time to get the fish out usually. The timer is KEY.
Here are a couple I took with no photographer. The camera was balanced on a rock on shore while I went in the water.
and this one was well over 50 pounds, so it CAN be done by yourself! (its not my best photo, but its better then nothing!
The camera went off before I was ready in this one...