Hi, have a 50 fisher retainer ^^ unfortunately it does not gather any non-crafting material fish.

46-50 is just Northern Pike & Cloud Cutter
41-45 is Silver Shark, Raincaller, Blacklip Oyster
36-40 is Whitelip Oyster, Velodyna Carp, Red Coral
31-35 is Indigo Herring, Ash Tuna, Fullmoon Sardine
26-30 is Blue Coral, Bianaq Bream, Black Sole, Hammerhead Shark

I can list the lower level fish if they are not already known, which I imagine they should be. I think it's worth it, since you can choose the fish you want, instead of hoping for them while fishing.