Students and staff from FSC Dale Fort Field Centre have studied limpet populations on Frenchman’s Steps shore for over thirty years. Variations in population density and age structure have been measured and in particular the effects of the Sea Empress oil spill have been investigated. The oil pollution reduced the population density significantly and affected smaller (younger) limpets in particular, especially those on the lower half of the shore. Since then further changes in limpet population density have occurred. These are interpreted in the light of long term oscillations in populations of barnacles and dogwhelks, which are related to the use (and subsequent banning) of Tri Butyl Tin anti fouling paint. Long term monitoring, using data collected by student groups, can be useful in highlighting variations in population density over time as well as being a worthwhile educational experience in its own right for the students and staff involved in the data collection.