User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-4098359-20110712124019/@comment-2194133-20110712230157

Peco sub probably just uses the volcano as another area that gives off another source of food, and when quests are to hunt it its just because it stopped to get food, plus it probably doesnt go to the sandy plains nor the deserted island or mountain stream due to food competition with  regular peco  so it has its own areas for food, i.e. the flooded forest and volcano.