Abstract
We report the first in situ observations of a large Taningia danae Joubin, 1931, close to the seafloor at bathyal depths of 2,157 m. The observation was made in the subtropical northeast Atlantic Seine seamount during daytime on 29 September 2012, over a silt-covered seafloor (33º40.1142′N, 14º22.7301′W). Seawater temperature was 4.2 ºC, salinity 35.40 ppt, oxygen saturation 50.87 Ox%, and pressure 2,178.29 dbar. Mantle length was estimated from imagery to be 65.3 cm (STD = 6.3). A repeated behaviour was observed every time the ROV approached: (1) swimming away from the ROV by flapping the fins twice (moving forward or backward), (2) gliding slightly inclined downward, until colliding against the seafloor, and (3) ascending obliquely or vertically in relation to the seafloor, finally evading the area moving upward using jet propulsion. These observations greatly extend the species depth range and document behaviour patterns. T. danae is able to explore beyond the mesopelagic zone where it has previously been reported.