A comparison of benthic biodiversity in the North Sea, English Channel and Celtic Seas - Epifauna

Comparison dataset of Animalia in the North Sea, the English Channel and the Celtic Sea. Samples were obtained by MAFF research vessels from 69 stations between 1992 and 1996.

A standard 2 m Lowesoft beam trawl with a 3 mm mesh codend liner was deployed for 5-10 min across each station at a speed of about 0.5 m/s. The "start" (locking of winch following seabed contact) and "end" (commencement of hauling) positions were recorded. Tow length averaged about 400 m, but varied substantially (s.d. = 290) depending on tidal current velocity and wind strength at the time of sampling. On retrieval of the trawl, an estimate of sample volume was made, along with a summary of the contents, noting especially the presence of stones, rock, etc. The sample was then sorted on deck over a 5 mm mesh sieve. Most specimens were identified and enumerated at sea. Any problematic specimens were preserved in formalin for identification on land.

The presence of infaunal organisms arising from the fouling of soft sediments was noted, as were occurences of pelagic species such as jellyfish. However, these records were excluded from the final compilation of the data. The former included most polychaete worms (with the exception of encrusting forms such as Sabellaria and Filograna, and surface-dwellling specimens within the family Aphroditidae), bivalve molluscs (excepting taxa with a surface-dwelling habitat such as Chlamys and Modiolus), and burrowing echinoderms such as Echinocardium and Amphiura.