All fish have stopped spawning

Started a server in pre-2 and shifted to pre-3 when it was released.

Fish occasionally have long periods in which they refuse to spawn in anywhere. Was mostly noticeable in pre-2 only in coral reef areas, though now in pre-3 all ocean areas seem to go many in-game days without spawning any fish at all. In the rare times they do spawn it is far less than originally showed up when the server was first started.