Anglerfish

Anglerfish are a type of fish native to Zeah. In order to catch this fish, players require level 82 in Fishing, a fishing rod, and sandworms. In addition, players also require 100% favour with the Piscarilius House in Great Kourend.

Upon catching an anglerfish, 120 Fishing experience is granted. Cooking anglerfish requires level 84 Cooking, and gives 230 experience. The burn rate for Anglerfish is exceptionally low at level 97 cooking with the Cooking Gauntlets, burning approximately 0.1% (1/1000), and they stop burning entirely at level 98 with Cooking Gauntlets, or 99 with the Cooking cape equipped. Burning anglerfish will result in a burnt anglerfish. The amount of Hitpoints healed is dependent on the player's Hitpoints level. At level 99, an anglerfish will heal 22. Anglerfish can also heal above maximum Hitpoints (making the maximum Hitpoints possible 121).

The amount of hitpoints boosted from eating anglerfish follows this table:

Formula for healing
The health boosted/restored seems to follow this formula: $$Health = floor(level / 10) + C$$

Where level is your base hitpoints level and C is a constant which differs depending on your hitpoints level as the following table shows: