PATTERNS OF MICROHABITAT UTILIZATION BY MOBILE MEGAFAUNA ON THE SOUTHERN NEW-ENGLAND (USA) CONTINENTAL-SHELF AND SLOPE

Video transects from occupied submersibles were used to define associa tions of mobile megafauna (primarily demersal fishes and crustaceans) with microhabitat features including shell, burrow, biogenic depressio n, biogenic depression with adjacent burrow, sand wave crest, boulder, and burrowed clay outcrop. Sites were located on low-relief bottoms a cross the southern New England (USA) continental shelf and slope at de pths of 55, 240, and 712 m. No significant diel differences in abundan ce were found for the 8 taxa censused at the 55 m (inner shelf) site. Non-random distributions and associations with specific microhabitats were found for the 8 taxa from diurnal transects and 6 taxa had non-ra ndom distributions from nocturnal transects. Silver hake Merluccius bi linearis and little skate Raja erinacea were associated with particula r microhabitats during the day but were randomly distributed at night. These shifts in pattern are attributed to diel differences in feeding behavior. Three of 6 taxa at a 240 m (outer shelf) site and 5 of 6 ta xa at a 712 m (slope) site showed non-random distributions and associa tions with specific microhabitats from diurnal transects. Observations with an ROV (remotely operated vehicle) at inner shelf sites (33 to 5 5 m) identified a distinction between species which produce biogenic d epressions and species which later occupy abandoned depressions. We po sit that associations with microhabitat features enhance individual fi tness possibly by reducing contact with potential predators and enhanc ing the ability to capture prey. Use of microhabitat features occurs i n assemblages where predators of focal organisms are abundant and poss ibly where prey density allows ambush predator tactics.