Catch per unit research effort: : sampling intensity, chronological uncertainty, and the onset of marine fish consumption in historic London

As the cumulative volume of ecofactual data from archaeological sites mounts, the analytical tools required for its synthesis have not always kept pace. While recent attention has been devoted to spatial aspects of meta-analysis, the methodological challenges of chronological synthesis have been somewhat neglected. Nowhere is this issue more acute than for urban sites, where complex, well-dated stratigraphy; rich organic remains; and multiple small- to medium-scale excavations often lead to an abundance of small datasets with cross-cutting phasing and varied chronological resolution. Individually these may be of limited value, but together they can represent the environmental and socioeconomic history of a city. The challenge lies in developing tools for effective synthesis. This paper demonstrates a new approach to chronological meta-analysis of ecofactual data, based upon (a) use of simulation to deal with dating uncertainty, and (b) calibration of results for variable research intensity. We apply this approach to a large body of historic-period fish bone data from London, revealing otherwise undetectable detail regarding one of the most profound shifts in medieval English economic and environmental history: the sudden onset of marine fishing commonly known as the Fish Event Horizon. Most importantly, we show that this phenomenon predates any visible decline in deposition of freshwater fish, and hence cannot have been driven by depletion of inland fisheries as has sometimes been suggested. The R package developed for this research, archSeries, is freely available.