Rocktail are fish found in Catherby. Rocktail require a minimum Fishing level of 90 and a harpoon to catch. They require a Cooking level of 93 to cook and stop burning at level 94 only if wearing brawling gloves (cooking). Cooking one inventory of rocktail, as with any food cooked in the same way, takes about 80 seconds.
Rocktail are the best type of food that heal your hitpoints in soulsplit. You could also obtain 100 per 12 hours using ::vote command.