Invertebrate surveys on shingle

To date, most effort to understand the ecology of shingle systems has been confined to botanical evaluation. Detailed recording of invertebrates is largely confined to Dungeness and Rye Harbour (Morris & Parsons 1991, Morris & Parsons 1992). However, ad hoc surveys and collecting activity by a variety of recorders provide wider indications of the faunas of some shingle systems (Shardlow 2001). There is considerable scope to expand our understanding of the invertebrate assemblages on particular sites.

The majority of invertebrate groups are represented on shingle structures, but some offer better opportunities for comparative studies and to put individual sites into context. These include the spiders, beetles and bees, wasps and ants, which are all readily taken in static traps. The lepidoptera (moths and butterflies) are also well represented, but are mostly taken at light traps or through active searching for larval stages. Lists of invertebrates are provided for dry shingle, damp shingle, man-made habitats on shingle and migrant species occurring on shingle.

Shingle is, however, extremely difficult to sample. The most effective quantitative sampling on shingle is trapping using pitfall and water traps, but a very large number of replicates are needed to yield statistically significant results. This has important logistic implications and means that detailed surveys will be comparatively expensive. Invertebrate surveys are highly specialised and require strong taxonomic and field craft skills. General netting and searching does not readily yield many specimens, but can be useful to augment the results from static traps.

There are strong possibilities that southern shingle systems in particular will yield a range of important records. This is because they lie at the extreme of the continental range of many species and are highly thermophilic, favouring those taxa that can cope effectively with extreme temperature fluctuations. The nature of the shingle matrix, including levels of finer sediment within the matrix, influence plant communities and vegetation structure, which in turn has a bearing on the invertebrate assemblage.

Whilst invertebrate surveys often lead to the removal of substantial numbers of individuals, this is an unfortunate necessity. Many species can only be determined with confidence following dissection. If substantial numbers of a rare species are taken, consideration should be given to moving traps. However, the levels of trapping that are likely to be afforded are unlikely to significantly affect populations.

References

Morris, R.K.A. & Parsons, M.S. 1991. An Inventory of the Invertebrate Fauna at Dungeness (Kent), Rye Harbour (E. Sussex) and Orfordness (Suffolk). Contract Surveys, 135 The Nature Conservancy Council, Peterborough.

Morris, R.K.A. & Parsons, M.S. 1992. A Survey of the Invertebrates on the Shingle of Dungeness, Rye Harbour and Orfordness. NCC Report, 77 Joint Nature Conservation Committee, Peterborough.

Shardlow, E.A. 2001. A review of the conservation importance of shingle habitat for invertebrates in the United Kingdom (UK). In: Ecology & Geomorphology of Coastal Shingle, eds.Packham, J.R., Randall, R.E., Barnes, R.S.K. & Neal, A.Westbury Academic and Scientific Publishing, 355-377.