A group of scientists, led by Kyle Van Houtan with the National Oceanic and Atmospheric Administration, asked “what did ocean ecosystems look like in the past?” Specifically the scientists wanted to know what the ocean ecosystem around the Hawaiian Islands was like in the past. And what long-term changes had occurred.
To answer this, the scientists set out to reconstruct past population changes of various fisheries species around the Hawaiian Islands. But historical data (before 1950) on fisheries catches and species’ abundance is very limited. So to supplement this limited data, the scientists came up with the idea to look at historical restaurant menus – This would tell them what seafood people were eating when. And then they could use this to infer how fish abundance may have changed overtime.
While changes in seafood consumption could merely reflect changes in consumer preference, more often, it is likely to reflect changes in species’ abundance and availability. When a fish species declines, human consumption of that species often declines as well [which is why today, depleted Bluefin tuna, Orange Roughy, and Atlantic Cod occur on menus far less often than they once did]. This is particularly true for places like Hawaii, where people primarily eat locally caught fish – And thus what’s on the menu reflects what’s in the water.
The scientists collected 376 Hawaiian restaurant menus dated between the 1920’s and 1970’s from 154 different restaurants. They got the majority of the menus from private collections, but they also got some from libraries and museums. They evaluated the presence of various fish species groups on these menus. And compared this to the limited historical fishery records they had from around 1905 and more recent catch data from the 1950’s onward.
The scientists’ analysis of the restaurant menus showed that near shore species, like reef fish, bottomfish (snappers and groupers), and jacks appeared frequently on menus before the 1940’s. But by the 1960’s these fish were on less than 10% of the menus sampled- suggesting these species had rapidly declined! This pattern is also reflected in the fisheries catch data. Early 1900’s catch records indicated high catches of near shore species. But when catch records pick up again in 1950, catches of these species are much lower and declining.
While the near shore fish were declining, fishermen began catching more large pelagic, offshore fish, like tuna, swordfish, and mahimahi. And these species began to appear more and more frequently on restaurant menus. By 1970, 95% of the menus sampled contained large pelagic fishes.
The restaurant menus helped fill in a missing gap in the fisheries catch data. And they provided insight into past population changes of ocean species. These historical menus are not just collectors’ items, they are valuable data. Perhaps more scientists will start digging up old seafood menus to see what they can learn.
To learn about how our oceans continue to change today, check out ‘Our Changing Ocean ’ section.
Elizabeth Brown is a research scientist at Blue Ocean Institute.