Examine the rod in your bags, click the 3 diff parts to activate/configure it.
Fly to Pakiat Bluffs area for updates is marked on map, use the rod to play hotter/colder type mini game to divine which tree is over charged. You will see your update tree has a glowing blue patch on it, may need to run around to find it. There will be a sparkling blue patch at the base of the tree for you to click. It may be behind a bush, but once the rod says that you no longer need it, the correct tree is next to you.
The rod will become a Piranha fishing rod. When you equip it, it will go into your Appearance slots.
Equip the rod, fly to Drukyna Marsh. The place you found the key for the quest.
Zap the bubbling parts in the water, note some are under water and maybe hard to see quickly, once zapped harvest the dead piranha fish in, 10 updates.