RATIONALE: This study presents the first sulphur isotope data of modern and 
archaeological cod (Gadus morhua) bone collagen, undertaken to identify 
large-scale spatial variability of significance as both baseline values for 
studies of human diet and a potential variable in isotope-based studies of fish 
trading.
METHODS: Collagen was extracted from modern and archaeological cod bones using a 
weak HCl solution and analysed for its sulphur isotopic composition by isotope 
ratio mass spectrometry (IRMS).
RESULTS: The archaeological cod have sulphur isotope values ranging from +9.1‰ 
to +18.2‰, whereas values for modern specimens range from +14.8‰ to +18.3‰. The 
modern data show values implying less freshwater influence, consistent with 
their offshore catch locations, but also corroborate some of the regional 
variability evident from the archaeological evidence.
CONCLUSIONS: The archaeological data have a large range of sulphur isotope 
values compared with the modern populations, probably indicating they were taken 
from a wide range of geographic locations, including both coastal and offshore 
locales. They show broad trends of regional difference that may relate to both 
the fish populations targeted (e.g. 'inshore' versus 'offshore') and the 
baseline values of the local ecosystem (e.g. degree of freshwater input from 
river systems).