Species point records from 1982 Dipper Wash sublittoral diving/dredging survey

This report notes the importance in the Wash of the sublittoral faunal populations, which may be a source of recruitment to the intertidal areas, for nature conservation and for fisheries. Although some information is available on the sublittoral of the Wash from remote sampling, very little diving has been done in the area due to low visibilities and strong tides. Although most of the area consists of mobile soft sediments, indications of some type of hard substratum are given by the masses of bryozoa and hydroids regularly washed up on the beaches. The aims of this preliminary survey were therefore to establish the feasibility of using diving to carry out a survey in this area, to collect information on the sublittoral, particularly in the Lynn Well area where 'rocky' outcrops were suspected and to make contacts with other organisations and individuals interested in the sublittoral of the Wash. The survey was carried out during a period of neap tides from a trawler owned by the Eastern Sea Fisheries Joint Committee. Two dives and three dredges were made. Descriptions of dive and dredge sites are provided, and species identified listed. No evidence of hard substrata was found, the sediments apparently consisting of muds and sands with a considerable amout of shell and pebble debris. The epifauna in the deeper areas dredged in Lynn Well was found to be fairly rich, with abundant hydroid material, Flustra foliacea and worm tubes attached to stones and shells on the sea bed. The infauna was also thought to be fairly rich, but only the top few inches of sediment could be sampled by dredge. In the Roaring Middle area a harder substratum may be present since little sediment was brought to the surface, and Modiolus beds are thought to occur here. Diving in the Wash is not a very effective method of survey due to the constraints of slack water and low visibility. However, it does provide a better indication of the composition and spatial arrangement of the communities and also allows collection of small organisms and other fragile material; information which may be lost from dredged collections. The report suggests therefore that diving would be a useful tool for backing up remote sampling methods in areas where interesting hauls have come to the surface.