Artificial seawalls are becoming increasingly common in marine and estuarine
intertidal habitats. These structures are replacing natural habitats at an alarming rate. Previous
studies have identified that the species found on artificial seawalls differ from the assemblages
found on natural rocky shores. Very few studies have examined if the behaviours exhibited by
species living on seawalls differ from the behaviours of species living on natural shores. This study
examines the foraging behaviour of the ecologically important grazing limpet Cellana tramoserica
in an attempt to determine if the behaviour of this species is consistent between natural rocky shores
and seawalls. Limpets were tracked throughout high tide and several components of their
behaviour were analysed. Additionally, chlorophyll a concentration and surface rugosity measures
were taken to try and identify the underlying causes of any variation in observed behaviour. This
study was done within Sydney Harbour, New South Wales, Australia where 50 % of the shore-line
is composed of artificial seawalls. Chlorophyll a concentration was shown to have a more patchy
distribution at spatial scales of lOs of centimetres on rocky shores and the surface rugosity was also
greater on rocky shores in comparison to seawalls. No significant differences in the total distance
travelled during foraging excursion or the direction of foraging routes were identified between the
two shores. There were, however, differences in rasping behaviour with rocky shore limpets
showing far greater variance in the rate of rasping. This study provides further evidence that
artificial seawalls can not be regarded as surrogates for natural rocky shores.
KEY WORDS: Seawalls . Artificial structures . Intertidal . Foraging Behaviour . Limpet .
Cellana tramoserica . Urban ecologySchool of Biological Sciences, The Centre for Research on Ecological Impacts of Coastal Cities,
University of Sydney, Australi
