An ecological interpretation of Mesolithic shellfish remains on the island of Oronsay, Inner Hebrides.
The island of Oronsay in the Inner Hebrides contains five Late Mesolithic
shell middens. This research uses ecological investigations on
limpets (Patella spp.), periwinkles (Littorina littorea L.) and
dogwhelks (Nucella lapillus L.) from the present Oronsay coast to aid
an interpretation of the shellfish collection strategies of the
Mesolithic hunter-gatherer populations, and to establish. the relative
importance of the three shellfish species in their diet.
Section A is devoted to ecological examinations of contemporary
limpets, periwinkles and dogwhelks, and in Section B this information
is applied to the midden shellfish. In chapter an examination is
made of previous research into selected aspects of the ecology of the
three species, which forms a necessary basis for the present research.
In each species an examination is made into studies concerning population
dynamics (reproduction and mortality), the distribution of the
animals over the shore, growth, and the physiological ecology of body
and shell development. Chapter 2 examines seasonal meat weight
changes (ie body weights) in animals from an area of the present
Oronsay coast at different tidal levels over a full year. For chapter
3 further fieldwork was carried out around the Oronsay coastline to
examine the difference in population structure of the three species in
varying coastal environments, and at different tidal levels. Attention
was paid to variations in size in each of the species, and their
relative proportions between sample sites. An examination was also
made of shape distribution of limpets at different tidal levels.
Chapter 4 makes comparisons between present Oronsay coastal environments
and those of the Mesolithic, with relation to coastal morphology
and exposure, and sea temperature, to assess the validity of using
contemporary data to interpret activities on Mesolithic Oronsay.
Section B begins with a brief synopsis of the main approaches that
have previously been adopted in midden studies. Chapter 6 then uses
information gained in chapter 3 to explain the size distribution of
each species in the middens, the shape distribution of the midden
limpets, and the relative proportions of the three species, in terms
of the collection strategies of the midden dwellers. Interactions
between the human predators and the shellfish populations will be
reflected in the size-frequency structure of the midden shellfish from
the base to the top of the middens. From sample columns in each
midden an assessment is made of the intensity and periodicity of
exploitation, and of the relative importance of each of the three
shellfish species. Chapter 7 uses data from chapter 2 to reconstruct
the relative proportions of meat weight provided by each shellfish
species in the middens. Account is taken both of shellfish size,
tidal position, and the varying amounts of meat which may have been
obtained at different seasons.
Seasonal changes in body weight are demonstrated in limpets, periwinkles
and dogwhelks from the present Oronsay coast, which are
related to their reproductive cycles and feeding intensities. When
this information is applied to the midden shells, at each possible
collection season limpets are shown to provide around 90% of the
shellfish meat weight.
On the modern coast the relative proportions of the three species vary
greatly from different shore environments, yet in the middens there is
a much greater uniformity in the relative numbers of the three
species. There are no major changes in species composition or size
upward through the middens, and it is argued that this indicates a
fairly low intensity, regular exploitation.