Habitat point records from 1994 DWT Beer Head to Chesil Cove (Lyme Bay) survey

This report forms part of a series of studies describing the environment of Lyme Bay on the south of Dorset and Devon, UK. The studies were commissioned as a prerequisite to exploration drilling for oil and gas within the bay by Kerr-McGee Oil (UK) plc and Partners. The study has been managed by Ambios Environmental Consultants Ltd. A nationally agreed protocol for quantitative or semi-quantitative sampling of boulder and cobble shores does not currently exist. Recognised techniques for rocky shore monitoring are not appropriate as many of the invertebrates on boulder and cobble shores hide beneath the boulders. The method adopted form this survey utilised a 10 minute timed search close to the time of low water (Smith, 1982). During the 10 minutes the shore was surveyed from just above the high water mark to the low water mark. If the boulders extended over the whole shore the survey was completed in two parts (upper and lower shore) with a 10 minute search in each part. At sites where boulders were only present on part of the shore, the survey was restricted to that zone. Boulders on a strip approximately 5 metres wide were turned over, invertebrates recorded and the boulders replaced. Any other material (eg strand line and wood) that might act as a refuge for invertebrates was also examined. NUmbers of invertebrates were recorded as accurately as possible, but some groups such as amphipods (sand hoppers) occured in such large numbers that only an estimate was possible. This semi-quantitative technique has been shown to be reproducible and produces valid results (Smith, 1982). Abundance scales based on numbers per unit area are not appropriate for this type of timed survey. The following abundance scale was adopted: Number counted in 10 minutes: 0..........Absent 1-3........Present 4-10.......Frequent 11-30......Common 31-100.....Abundant >100.......Super Abundant The objective of this survey was to provide a baseline against which to monitor and change in the diversity of fauna living on and under cobbles and boulders in the eastern part of Lyme Bay. Five sites were chosen, from Charmouth in the west to Fortuneswell (on the Isle of Portland) in the east. A total of 32 taxa were recorded from these sites. The number of taxa recorded at each site ranged from 3-15. It is suggested that the site with the lowest number of taxa may be affected by disturbance from holidaymakers, and that another site with a low number of taxa may be affected by pollution. Some groups that would have been expected in reasonable numbers were either absent (eg oligocheate worms) or present at very low densities (eg mussels and nemertean worms). None of the species recoreded is scarce or rare. Analysis of the data from these sites suggests that they should all be classified as being of 'Local' importance in conservation terms, but in some cases inclusion of data from other habitats at the site will alter the classification.