Here is the full list of all 21 Pacifish achievements. It takes around 80-100 hours to unlock all of the achievements on Windows.
Complete 50 thousand catches
Eat 10 million fish
Find all five shells
Acquire Sam's journal
Own all tackle
Own all fishing poles
Unlock Dam and Sky fishing
Defeat all bosses
Reach Fisher level 100
Find the Black Orb
Earn 500 million coins
Reach fight area 100
Defeat 50 thousand enemies
Earn 50 million pixels
Hatch 10 million fish
Spin reels 50 thousand times
Craft 20 fishing pole mods
Get 1000 matches
Reach Market level 50
Use 1000 bait
Reach Swimmer level 10