(Could menus like these provide valuable information on fish populations? Image courtesy of Cool Places--and Falmouth's The Shack.)
The researchers compare menus to the middens that are studied by archaeologists and historians. In colloquial terms, middens can be described as dumps or trash heaps, and are created by many species, including humans. Examination of middens allows researchers to investigate what ecological products have been utilized by an animal or society, as well as to study how consumption of that resource affected the local environment. Menus could be a modern counterpart to this, with analyses of their contents shedding light on which species were consumed during particular eras, how readily available they were, and how highly prized particular catches were relative to others. Indeed, previous researchers have already used menus to extract information about the popularity of certain seafood catches. In the current study, however, the authors were more interested in determining whether menus might reflect the local abundances of edible marine wildlife populations.
To explore this, the researchers collected 376 menus from 154 Hawaiian restaurants ranging from local dives to fancier sit-down establishments aimed at tourists. They focused on Hawaii because of its distance from the mainland; restaurants on the islands generally only serve locally sourced seafood, making the results of the study more easily interpretable. The menus cover nearly a fifty-year period (1928-1974) and were supplemented by government data on local fishery activity. These official records classified fish into five guilds (small pelagics, large pelagics, jacks, bottom fish, and reef fish); the researchers applied this same classification scheme to the fish found on each menu.
(A black jack, one of many jacks found off the coasts of Hawaii. Species like this declined in prevalence on restaurant menus from 1935 onwards, and became particularly uncommon after 1960. Image courtesy of Lurebook.)
Hawaii's nearshore fishery stocks decreased between 1940 and 1959, prompting the growth of pelagic fisheries; commercial landings of jacks, bottom fish, and reef fish all declined during this time. Likewise, the proportion of menus featuring these species markedly decreased from 1930 onwards, bottoming out around 1960. As the pelagic fishing industry took off in the late 1950s, restaurant menus featured an increasing number of both small and large pelagic fish species; by 1970, 95% of restaurant menus contained at least one large pelagic species.
For all five guilds examined here, curves for commercial landings are surprisingly similar to those for menu contents, though offset by a few years. This discrepancy may have been driven by public preference: Diners might have needed a few years to adjust to the idea of eating new types of fish (though the increasing scarcity of familiar species was likely a good incentive). Market availability might also have influenced the trends; animals that were landed may not always have been sold to restaurants, but instead may have been used for bait, sold to grocers, or consumed by the fishermen themselves. Regardless, menu content does seem to provide a rough estimate of the local abundance of edible fish species, suggesting that other researchers might be able to extract useful data from this unusual source of information.
(Certain menu items, including mollusks, frogs, and shrimps, did not reflect local populations of wild animals. This is because the seafood was either imported or raised in aquaculture. Image courtesy of The Pocahontas Files.)
That said, the authors do raise a number of potential issues with the use of restaurant menus in scientific research. For one thing, some species were more accurately represented than others. Mollusks and shrimps, for example, were generally imported from elsewhere, meaning that the menus did not provide much information on Hawaiian populations of these animals. Frogs, on the other hand, were produced by aquaculture rather than wild capture, and turtle meat was more likely to show up in local markets than in restaurants. In other words, researchers should familiarize themselves with the local seafood culture (fishing, eating, market dynamics, sourcing, public opinion) so that they can accurately interpret menu patterns.
For those intrepid scientists who decide to take on this challenge, the authors note that it could be interesting to conduct analyses not just of which species are featured, but also how much they cost--after all, particular dishes may continue to be served long after an animal has become rare, but this is likely to be accompanied by a noticeable hike in price.
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Van Houtan, K.S., McClenachan, L., and Kittinger, J.N. 2013. Seafood menus reflect long-term ocean changes. Frontiers in Ecology and the Environment 11:289-290.