Cuba says U.S. scientists won't get immediate access to potentially invaluable fishing logs kept by Ernest Hemingway but authorities will work to let researchers see them eventually.

Cuba's National Cultural Heritage Council said Thursday that marine scientists on a tour with the author's grandsons wouldn't be able to see the logs before the group returns to the U.S. on Saturday.

Scientist David Die says he's optimistic about eventually being able to see the logs, which may contain enough details about the Nobel laureate's decades of game fishing off Cuba that they help measure how much sport-fish populations have declined due to overfishing.

Sport fishermen's records typically contain details of the numbers of fish caught and their size and are some of the only resources for scientists measuring such declines.