Fish farming tracked from fragmentary remains using a universal bone barcode

Archaeologists and historians working in medieval Britain have long acknowledged the social and symbolic importance of fish consumption. Associated with fasting as a feature of the Christian calendar, fish grew in importance to the diet c. 1000AD: this increasing in marine fish consumption has been called the 'fish event horizon' and is visible on numerous archaeological sites, as well as in the human bone stable isotopic record. Freshwater fish farming was introduced to Britain in the years following the Norman Conquest, and their circulation as gifts seems to have encouraged the proliferation of fish ponds on many ecclesiastical and secular elite sites. There are, however, a number of points on which historians and archaeologists currently beg to differ. Among these, the farming of carp in Britain is a source of considerable controversy.

Carp were introduced to western Europe as an ideal species for fish farming. By the mid 13th century they were being farmed in France, becoming relatively common across western Europe from the 14th century onwards. Contemporary historical records from Britain describe the farming of native cyprinids such as bream, but it is not until the mid 15th century that carp appear in documents, leading some historians to conclude that '...by the end of the sixteenth century... the carp had become the most popular freshwater fish in England'. This all sounds convincing, but there is a fundamental problem. This claimed growth in popularity cannot be traced at all in the archaeological record. Chance survival of diagnostic elements means that we now have the earliest archaeological evidence for British carp, in the same century as the first historical record. Nevertheless carp are rare on medieval and later archaeological sites in Britain - in sharp contrast to the continental evidence.

There may be several reasons for these differences of observation and opinion, but one thing, at least, is clear. The character and condition of many fish bone assemblages makes it very difficult indeed to differentiate cyprinids to individual species.

This is where ZooMS - short for Zooarchaeology by Mass Spectrometry - comes in. Even the smallest fragment of bone contains a protein 'barcode', in the form of a collagen sequence. Using protein mass spectrometry we can rapidly and cheaply speciate every cyprinid element, even fish scales. Combine an abundant protein with a sensitive method of detection, and you have a fast, cheap identification system. We can use ZooMS to monitor changes in frequency of different cyprinids over time. This will not only clarify just how and when the farming of carp became significant in the medieval world. It will also allow us to examine changes in medieval water quality (as reflected in cyprinid species distribution).

If ZooMS proves to be a success we could rapidly survey cyprinid stocks in 'fishponds' using just 100 mm cores. Indeed, the ability to potentially fingerprint every bony element (mammals, birds, fish) has the potential to revolutionise archaeological survey.