A Comparative Investigation into the Foraging Behaviour of the Intertidal Limpet eel/ana tramoserica on Artificial Seawalls and Natural

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