Santander, February 19th-22nd 2008 - Aranzadi

Oysters ancient and modern: potential shape variation with habitat in flat oysters (Ostrea edulis L.), and its possible use in archaeology
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Figure 2. Growth steps in oval late Roman oysters from Staple Gardens,
Winchester. (a): slight growth step (posterior of original shell arrowed) (Hmax:
110mm); (b): step change from round to oval morphotype (Hmax: 96mm); (c):
typical oval morphotype hinge, showing growth step (white arrow) (Hinge width
Wh: 23mm); (d): hinge showing growth-step from typical O. edulis hinge to typical
oval morphotype (Wh: 24mm).
Also, breakage rates can be very high in
archaeological shell, with loss of the margins rendering
most oyster shells unfit to measure.
Another aim was to determine whether it is likely
that there are consistent relationships between
shell features which survive well in archaeological
oysters and overall shell size, so that archaeological
oyster shell sizes can be estimated.
2. MATERIAL
One late Roman deposit, context 2239, a fill in a
pit of the site’s Phase 2.3 (Late Third – mid Fourth
Century A.D.) provided oysters in statistically useful
numbers: 56 upper valves (none complete enough
to be measurable) and 74 bases, of which 40 were
measurable. This was an individual layer within the
pit, and it was likely that it was a single depositional
event. Winchester lies about 20km upriver from
Southampton Water, one of the four bays in the central
southern English coast used as harbours (Fig.
3). The harbours empty and fill twice a day due to
the tides, via channels locally called ‘lakes’. The
coast is separated from the Isle of Wight by the
broad strait called the Solent. Tidal currents in the
Solent and along the coast are strong, up to 2 m/sec
(Velegrakis 2000, 33) forming sand and gravel
dunes and maintaining a natural channel up to 28m
deep down the Solent (Dyer 1971), while the beds
of the harbours and lakes are fine mud and muddy
sand (Dyer 1980: Fig. 2).
Most samples of oysters were taken at recorded
positions from known commercial beds, by
local governments as part of the monthly programme
monitoring oyster food safety, and assessed
by the Health Protection Agency’s Wessex
Environmental Microbiology Service (WEMS),
Southampton. Samples were selected to compare
harbours, and to approximate a transect across
Figure 3. Locations of modern comparative samples of O. edulis.
MUNIBE Suplemento - Gehigarria 31, 2010
S.C. Aranzadi. Z.E. Donostia/San Sebastián