Occurrence and activity of mobile macrofauna on a sublittoral reef: Diel and seasonal variation

Underwater television observations were made of mobile macrofauna inhabitin g two parts of a sublittoral reef on the west coast of Scotland for 48h per iods in spring, summer, autumn and winter. Continuous occurrence profiles ( mean hourly frequency of occurrence, %) were detailed for 12 species of fis h (Chirolophis ascanii, Conger conger, Ctenolabrus rupestris, Lepadogaster candollei, Myoxocephalus scorpius, Pholis gunnellus, Pollachius pollachius, Raniceps raninus, Phrynorhombus regius, Zeugopterus punctatus, Thorogobius ephippiatus and Trisopterus minutus), ten crustacean species (Cancer pagur us, Carcinus maenas, Galathea strigosa, Homarus gammarus, Inachus spp., Mun ida rugosa, Necora puber, Brachyuran sp., Caridean sp. and Pagurid sp.) and four echinoderm species (Antedon bifida, Asterias rubens, Henricia oculata and Solaster endeca). Rhythmic patterns of diel activity and/or occurrence were identified for several species. Chirolophis ascanii, Ctenolabrus rupe stris, L. candollei, Myoxocephalus scorpius, Pholis gunnellus, Pollachius p ollachius, Thorogobius ephippiatus, Trisopterus minutus and Munida rugosa w ere predominantly diurnal, but Ctenolabrus rupestris, Myoxocephalus scorpiu s and Trisopterus minutus also showed some evidence of crepuscular activity . Raniceps raninus activity was predominantly nocturnal but became continuo us in summer. In other species (the topknots Phrynorhombus regius and Z. pu nctatus and the crustaceans Cancer pagurus and Homarus gammarus) identifiab le occurrence patterns changed with season or site. The greatest number of fish species occurred in winter with Myoxocephalus scorpius, Pollachius pol lachius and topknots (Phrynorhombus regius and Z. punctatus) showing greate r occurrence/activity during spring and winter. Go-occurrence analysis was used to identify species interactions or avoidances.