Abstract
Land-based visual observations will be carried out by observers on a hilltop on the island of Eday, overlooking the Fall of Warness tidal site in Orkney. Watches will be carried out by an experienced observer during daylight hours, ranging between 04:00hrs and 20:00hrs during summertime. The study area will be scanned and the time and location of any marine mammal or seabird sightings will be recorded. Where possible, the geographic location of each marine mammal or seabird group will be recorded using a pre-defined grid. Although marine mammals and seabirds will be identified to species whenever possible, due to the difficulty in differentiating between marine mammal and bird species, especially at distance, additional categories of 'unidentified species' will be included in the species list. Additional information about species sighted will be collected. For marine mammals, group size will be estimated if animals are seen in groups and the location of the centre of the group will be recorded. Prior to this study, the frequency of use of the Fall of Warness by these animals was unknown.
Surveys will encompass all states of tide and times of day (during daylight hours) in a systematic manner to ensure there is appropriate sampling of all environmental states. Tide state will be defined in relation to time since the previous high tide recorded at Kirkwall. Data on several weather variables including precipitation, sea state, cloud cover, and wind speed and direction will also be recorded. Data will be recorded on paper sheets by the observer and then transferred into an Excel spreadsheet.
Data from the land-based study described here will provide information on distribution and 'relative' abundance of animals in and around the study area. To inform the analysis on the reliability of detecting animals from a land-based vantage point, the land-based observations may need to be augmented with boat-based surveys along transect lines placed perpendicular to the coast. This information would then enable variations due to detectability differences to be distinguished from genuine changes in abundance, yielding more robust impact analysis. Monitoring of a site with similar characteristics to the test site, yet undisturbed by the presence of tidal energy devices, may be valuable in relating any changes observed to the tidal devices.