Fifty years of cetacean sightings from the Cornish coast, SW England

Abstract

There are very few data on changes in status of smaller cetaceans around UK coasts, including Cornwall. To fill this gap a quantitative retrospective survey of the dolphin Cetaceae sightings of 1000 people in Cornwall has been carried out. This included a simultaneous survey of other maritime sightings as control events, in order to provide some indication of possible errors arising from variations in observer effort or memory distortions. The events chosen for use as controls were coastal sightings of basking sharks Cetorhinus maximus and of waterspouts or funnel clouds. The results indicate a profound reduction of sightings during the last 50 years, occurring throughout the period. The decline appears to affect larger groups particularly, with sightings of small groups of dolphins showing no change and sightings of single dolphins showing an increase. The survey suggests that the method is capable of yielding useful results. Its value could probably be tested and greatly increased by repetition elsewhere around UK coasts, creating the possibility of detecting varying temporal and spatial patterns of change, with possibly some discrimination of the species involved. Such variations might throw light on the major causes of changes that are of great conservation importance.