I don't know if it's a feature, but in my first village the master farmers caught two fish in the lagoon: the first one was just a fish (one of the ones from Fish Tycoon) and the second was the magic fish of fertility for the puzzle. None of the villagers have seen anything in the lagoon since. Personally I blame the amount of laundry they do - a village of 90 does not required 20 odd people doing laundry at once.