The abundance of fishes served at restaurants provide clues to the quantities of fish species in the ocean.

Fisheries scientists recently compared nearly fifty years of Hawaiian seafood restaurant menus to government fisheries statistics and records of fishers’ harvests. The researchers found a correlation between the two numbers. When statistics showed certain fish abounded in the waters around Hawaii, those same fish ended up on the menu at local restaurants.

SEE ALSO: Top 10 Back to School Brain Foods

That the catch of the day ended up on the menu isn’t particularly surprising, but it does suggest that menus can be used as indirect sources of evidence about local fish population changes when scientific measurements don’t exist. Though trusting menus alone could be misleading; today, many still offer shark-fin soup despite the clear evidence that sharks are endangered.

Still, seafood menus could serve like the shell middens used by archeologists, suggested the study authors in Frontiers in Ecology and the Environment. Shell middens are the refuse heaps left behind by ancient coastal peoples. The heaps provide evidence of what foods were available and how consumption patterns changed over time. Menus can serve as the modern equivalent since the menus reflect how frequently certain fish are available, even when hard data doesn’t exist. Taking into account the price of the seafood offered would also improve such research.

The seafood menus that the authors studied covered a 45 year gap in official fisheries records. The menus provided a rare record of how fish populations changed as Hawaii moved towards statehood.

The menu study analyzed 376 menus from 154 Hawaiian restaurants between 1928 to 1974. Before 1940, coastal and reef fish were most common. However, by the time of Hawaii’s acceptance into the United States in 1959, large, deep-water oceanic fish dominated restaurant menus. Ninety-five percent of restaurant menus contained oceanic fish by 1970.

IMAGE: A waitress taking a breakfast order at Kahala Hilton Hotel, Hawaii, USA in 1989 (Alan Light, Wikimedia Commons)