Underwater television observations of Serpula vermicularis (L.) reefs and associated mobile fauna in Loch Creran, Scotland

The behaviour of Serpula vermicularis reef worms and associated mobile fauna in Loch Creran, on the west coast of Scotland, was recorded for six weeks using underwater television. The reef worms were extended almost continually, generally only retracting when stimulated by the close proximity of a predator. The length of hiding time varied according to the species triggering the reaction. The mean length of time retracted was 21 s. Fauna associated with the reefs included the corkwing wrasse Crenilabrus melops, ballan wrasse Labrus bergylta, black squat lobster Galathea squamifera and velvet swimming crabs Necora puber. There were few significant associations between tidal cycle and the presence/activity of associated fauna but a number of fish and crustacean species appeared to be influenced by the diurnal cycle. Gobies were recorded during daylight only with peak observations around midday while wrasse, butterfish Pholis gunnellus and cod Gadus morhua were crepuscular. The dawn and dusk appearance of juvenile cod in large shoals is suggestive of a nightly migration.