MEPS 257:223-232 (2003)  -  doi:10.3354/meps257223

ABSTRACT: Much is known in very broad terms about the distribution of deep-sea fishes, but information on fine-scale habitat selection and behaviour in the largest living space on earth is still rare. Based on video sequences from 4 dives performed with the manned submersible ŒNautile¹ at depths between 400 and 2000 m in the Bay of Biscay, NE Atlantic, we studied the behaviour of co-occurring slope-dwelling deep-sea fishes. Five different habitats were identified according to depth range or topographical and hydrological characteristics. For each fish species or genus that could be identified, estimates of absolute abundance were provided. The most frequently occurring species, roundnose grenadier Coryphaenoides rupestris, blackmouth catshark Galeus melastomus, bluemouth Helicolenus dactylopterus dactylopterus, orange roughy Hoplostethus atlanticus, North Atlantic codling Lepidion eques, greater forkbeard Phycis blennoides, and northern cutthroat eel Synaphobranchus kaupi were quantitatively compared with respect to the relative frequencies of disturbance responses to the submersible, locomotion behaviour, and vertical positioning above the bottom. Clear variations in behaviour and abundance among species and habitats were found, reflecting both species-specific and flexible adjustment to small-scale spatial and temporal variability on the Bay of Biscay continental slope. These results have important implications for the development of sustainable deep-water fisheries management.

KEY WORDS: Submersible observations · Assemblage structure · Density · Locomotion · Vertical positioning · Foraging · Species-specific · Behavioural flexibility