Stable Isotope Evidence for Late Medieval (14th–15th C) Origins of the Eastern Baltic Cod (Gadus morhua) Fishery

David Orton ,Inge Bødker Enghoff,Daniel Makowiecki,James H Barrett,Colin Amundsen,Anne Karin Hufthammer,Alison Locker,Jennifer Harland,Anton Ervynck,Cluny Johnstone,Wim Van Neer,Brian R Mackenzie,Tessa De Roo,Lembi Lõugas,Sheila Hamilton‐Dyer ,Michael P Richards ,Tamsin C O’connell ,Peter E Pope ,Lennart Jönsson ,D Heinrich ,Andrew Jones

doi:10.1371/journal.pone.0027568

Abstract

Although recent historical ecology studies have extended quantitative knowledge of eastern Baltic cod (Gadus morhua) exploitation back as far as the 16th century, the historical origin of the modern fishery remains obscure. Widespread archaeological evidence for cod consumption around the eastern Baltic littoral emerges around the 13th century, three centuries before systematic documentation, but it is not clear whether this represents (1) development of a substantial eastern Baltic cod fishery, or (2) large-scale importation of preserved cod from elsewhere. To distinguish between these hypotheses we use stable carbon and nitrogen isotope analysis to determine likely catch regions of 74 cod vertebrae and cleithra from 19 Baltic archaeological sites dated from the 8th to the 16th centuries. δ13C and δ15N signatures for six possible catch regions were established using a larger sample of archaeological cod cranial bones (n = 249). The data strongly support the second hypothesis, revealing widespread importation of cod during the 13th to 14th centuries, most of it probably from Arctic Norway. By the 15th century, however, eastern Baltic cod dominate within our sample, indicating the development of a substantial late medieval fishery. Potential human impact on cod stocks in the eastern Baltic must thus be taken into account for at least the last 600 years.

Highlights

Overview and hypotheses Recent studies of eastern Baltic cod (Gadus morhua) populations - within the framework of the History of Marine Animal Populations project - stress the importance of time depth for understanding impacts of interactions between fishing mortality and other factors on stocks [1,2,3,4,5,6]
Cod consumed around the eastern Baltic littoral during the medieval period were overwhelmingly imported, with a local eastern Baltic fishery developing subsequently
The present study seeks to illuminate these distinct yet interrelated variables by tracing the geographical origin of cod consumed in the Baltic Sea region, from the 8th century until the emergence of systematic catch statistics in the 16th century

Summary

Introduction

Overview and hypotheses Recent studies of eastern Baltic cod (Gadus morhua) populations - within the framework of the History of Marine Animal Populations project - stress the importance of time depth for understanding impacts of interactions between fishing mortality and other factors on stocks [1,2,3,4,5,6]. The present study seeks to illuminate these distinct yet interrelated variables by tracing the geographical origin of cod consumed in the Baltic Sea region, from the 8th century until the emergence of systematic catch statistics in the 16th century. In so doing it informs the economic and environmental ‘history’ of Europe, while demonstrating the need to consider cultural factors that may lead to unexpected and counter-intuitive twists within an overall human trend of using increasingly distant resources [13]

Methods

Results

Conclusion