Poltergeist

The Poltergeist is the second most valuable fish of the 742 documented ones. Its average value is C$1,850,000, a figure no ordinary catch gets near, and that is the first thing to know before deciding whether to chase it.

It belongs to the Special rarity and appears during the Admin Event called Spectral Tide, in Foggy weather. The data does not list a bait, a time of day, a season or a weight range for it, so there is nothing to prepare in advance except being in the event while it is live. The in-game description calls it a malevolent and chaotic spirit that hurls objects and sows terror with unpredictable disturbances.

Because it is tied to an Admin Event, access depends on when that event runs, not on anything you can force with gear or routine. The practical advice is simple: do not build a plan around it. If Spectral Tide is active and the fog rolls in, drop what you are doing and fish, because a single catch is worth more than a very long session of regular fishing. If the event is not running, spend your time on fish you can reach on demand, and keep this one in mind as a lucky event windfall instead.