Samoan palolo worms swarm on set nights in the last quarter; Californian grunion come ashore to spawn in the few nights after the highest tides and wriggle back on the next wave.

Both are timed to the Moon and both are predictable enough to have a festival or a fishing licence built around them. The grunion in particular depends on it: the eggs are buried above the reach of ordinary tides and hatch a fortnight later when the next spring tide uncovers them, which only works if the parents can read the calendar.