As of Chapter 2 Season 5 there are now 10 (technically 11) fish in Battle Royale, with the newly updated and expanded fishing mechanic. There are 39 (+2) unique fish models, but there are only 9 different categories of fish. Each of the 9 fish has different effects.
The Flopper heals 50 Health and can be consumed at any level of HP below 100.
The Slurpfish heals 50 effective Health and can be consumed at any level of HP below 100 Health and Shield. Any remaining Health restored by the Slurpfish will be converted into Shield, hence the name 'Slurp'.
The Spicyfish will give the player 15 Health and grant the player a temporary speed boost, just like the Pepper. It can be consumed at any level of HP.
The Hop Flopper will grant the player 15 Health and a temporary low gravity effect, in the same manner as Hop Rocks. It is possible to consume it at any level of HP.
The Jellyfish, when consumed, will grant the player 20 effective Health and will restore the same amount to anyone in the vicinity in the same manner as a Chug Splash. It is possible to consume it at any level of HP below 100 and, unlike a Chug Splash, which is thrown.
The Shieldfish will grant the player 50 Shield, in the same manner as a Shield Potion. It is possible to consume it at any level of Shield below 100.
The Thermalfish will grant the player 15 Health and a temporary thermal overlay, similar to the one incorporated in the Thermal Scoped Assault Rifle, but with a Black and White overlay, instead of a blue and red one. It is possible to consume it at any level of HP.
The Small Fry will grant the player 25 Health up until 75, similar to Bandages. You can't consume it above 75 Health.
The Vendetta Flopper grants 40 Health and marks nearby enemies, similar to how a Shakedown or Flare Gun works.
The Midas Flopper grants 40 Health and turns a player's inventory entirely to legendary items.
There is also a 1 in a million chance to catch a Mythical Goldfish. When thrown, it does 200 damage and can be picked back up and used more than once. However, it is not technically a fish, but a trophy and a weapon.