Answer:
A ghostly reminder means something that, like a ghost, shows something is no longer alive and also reminds us of what we have lost.
Explanation:
The author describes harbor towns, such as Cape Cod and Oyster Bay, as “ghostly reminders” because, in the present, they only vaguely suggest the marine life that used to be found in those places. There are no more cod nor oysters, because of overfishing.
