User blog comment:Plexioth- xD/Monster Hunter 3 Ultimate/@comment-12265783-20130831144217/@comment-8874090-20130831153157

What MHRango said, but I think you can't get speartuna from the fleet. You can catch it on quests. I got mine in the flooded forest (area 4). You can easyly recognise it by being almost as big as the hunter.