How do you gain treasure from fishing?

Receiving treasure from fishing has an equal chance in every biome.

Below is a graph showing the chance of getting treasure with each enchantment stage of Luck Of The Sea:

Item None Stage 1 Stage 2 Stage 3
Treasure 5% 7.1% 9.2% 11.3%
- - - - -
Bow 0.8% 1.2% 1.5% 1.9%
Enchanted Book 0.8% 1.2% 1.5% 1.9%
Fishing Rod 0.8% 1.2% 1.5% 1.9%
Name Tag 0.8% 1.2% 1.5% 1.9%
Nautilus Shell 0.8% 1.2% 1.5% 1.9%
Saddle 0.8% 1.2% 1.5% 1.9%

Source: minecraft.fandom.com