Just last night I set out to get a catfish. I fished many cherry salmons and black bass before I finally got it. I know you said you know the shadow sizes, but remember the catfish will only spawn in the pool part of the river. What I did was was save & continue while at the pool and fished out anything that was there. Rinse & repeat until catfish. I don’t have any advice for the angelfish though, I got that one quite accidentally.
My next venture will be capturing a char. Another tricky fish now that I’m remembering from doing this last year on a different game file.
I accidentally caught both last night, I was fishing for things to sell (since I decided to get rid of all my bells and do things by earning it), I've caught the catfish before and he's creepy so of course the game has me catch two, and the angel fish was a surprise. so that was good.