River Rapids Wrangler

Sadly this is now totally undoable. They fixed the exploit and now the rest of us are stuck with a buggy minigame. The net often doesn't catch anything even when you throw it with complete accuracy. The camera goes nuts when the boat turns making aiming even harder.

The fish respawn

The best tip I can give is in the beginning start throwing your single net (the range is quite far) ASAP so you get their respawn timer going and as you progress pan your camera around and snipe some respawning ones. I was able to score 4 or 5 more on average before leaving the first area after realizing they respawn and that made all the difference. With a little warmup and planning which fish you want to get the further down stream, you can get this in no time.

Took me and my stubbornness about 45 minutes of trying this before realizing they respawn and I then got it down in a few more attempts afterwards.

You can cheat here....
Just try the achievement as normal - but instead of getting teleported up after failing just fly your dragon
Start a new run
You will lose the buffs from the run before but the count is still running
Catch the remaining fish
gg