Hidden level:
Complete the game having caught 70/70 fish and all 18 stages cleared to unlock Panda Lake in free mode. Panda Lake is a cartoon stage with 2D cartoon fish. The fish you can catch here are Cup Shrimp, Drowned Panda, Eat-a-Lot Shark, Nice Squid, Poison Starfish, Porcupine Fish, Sava-Dava, Striped Catfish and Thirteen Fish.

Glitch: Spelling:
When You Catch A Whitespotted Char on the "Trout Fishing" level, Char will be spelled "Cher".

After you catch a pond smelt in the "Ice Fishing" level, go to the fishing notebook. Pond Smelt will be spelled "Pound Smelt".