Hawaii's Restaurant Menus Have Chronicled the Decline of Its Coral Reefs

A taste for green sea turtle meat and eggs has led to the giant reptile becoming endangered, but don't blame restaurants in Hawaii, where many green turtles live. A study designed to determine whether the turtle historically appeared on restaurant menus in Hawaii has had an unintended side effect: It's allowed researchers to track fish populations near the island.

"The whole point was to see if there was sea turtle on the menu, to see if tourism drove sea turtle catches," John Kittinger, of Stanford University's Center for Ocean Solutions said. "There was no turtles on any of the menus at all. But then we decided to look and see what else was there."

It's a novel idea, and one that the biologist says hasn't been undertaken before. But he and his team, who published their research in Frontiers in Ecology and the Environment this week, correlated menu offerings with local fishery data and found that they aligned closely. In fact, the data may be able to fill in gaps in fishery data that exist in the 1930s, when fishery statistics were lacking.

"Menus are a function of consumer preference, but we think that, based on the existing science, the changes have been driven more by availability than by preference. Some of the fish disappearing from menus are still highly prized," he said. "As we overfish, as climate change and pollution take its toll, that shows up on the menus. They're a proxy for what's happening in the ocean."

Besides the kind of odd appearance and sudden disappearance of frog legs and the skyrocketing popularity of beef on menus, Bishop noted that near-shore catches of reef fish—once plentiful in restaurants—barely appear on menus two decades later. Meanwhile, large offshore fish such as ahi tuna and mahi-mahi became much more popular. Imported and farm-grown fish have also become more popular as fish catches declined.

"Reef fish, jacks, and bottomfish were common on menus before 1940, but by Hawaii’s state-hood in 1959 these items appeared collectively on less than 10% of the menus sampled," the authors wrote.

So how does one go about tracking down 376 menus—dated between 1928 and 1974—from 154 Hawaiian restaurants? Surprisingly, there's a market for antique menus: The New York Public Library has an extensive set of menus from 1851-1930, Cornell has another large collection, and Kittinger says he managed to track down a lot of the menus from private collectors.

For this study, the majority of menus came from a collection at Honolulu's Bernice Pauahi Bishop Museum, which chronicles the state's natural and cultural history. As he became involved in the sea turtle research, he realized that menus could provide more information.

"This all happened by accident. We wanted to see if we could use it as a data source, then we realized there was a whole lot of them," he said. "It was one of those real organic happy accident kind-of-things that sometimes happens."

Though the conclusions you can draw from menus are subjective, coupled with fishery information, they provide an important extra data point, according to Loren McClenachan, a co-author of the paper.

"Historical ecology typically focuses on supply-side information," she said. "Restaurant menus are an available but often overlooked source of information on the demand side. They document seafood consumption, availability and even value over time."