Stardew Valley Odd Bug

[lizjacq]

I had an issue with getting perfection in Stardew Valley. I am so close but I can't get the mutant Carp. It was the last thing I needed. However, I have fished and fished and fished but I can't get it. I have a Master's Iridium Rod and I have eaten food with a +4 fishing bump. I have done everything possible but all I catch is carp. I can even catch the Mutant Carp's son, but I can't get the Mutant Carp. What's happening?

[Queen Droxxanna]

mutant carp are found in the sewers. go fishing in the sewers.