Glenn Jones, of Texas A&M University, is a palaeo-oceanographer—an archaeologist of the oceans. He investigates both the mysteries of the deep and the secrets of the past. He and a colleague once estimated the temperature of the sea floor a century ago by studying the “isotopic composition” of mollusc shells. His latest method of inquiry, on show this week at the “Oceans Past” conference in Kolding, Denmark, is a little easier to understand. He reads old seafood menus. Lots of them. Mr Jones reckons he and his team have trawled through 40,000 or so, dating back as far as the 1850s.
Why? His menus, mostly from American cities on either coast, have allowed him to track the price of seafood back 150 years, much further than anyone has gone before. The menus show that the bountiful seas of centuries past have become more miserly in recent decades. From the early 1920s to the late 1930s, for example, a San Francisco restaurant would charge only $6-7, in today’s money, for a serving of abalone, a type of mollusc. By the 1980s, however, abalone was selling for $30-40 a meal. The collapse of abalone stocks prompted a 1997 ban on commercial harvesting off California’s coast.

“When lobster was fertiliser,” The Economist, October 27, 2005
Hobnob Blog has more: “‘When lobster was fertiliser’ – What we can learn from old restaurant menus,” November 2, 2005