2023_programme: Individual daytime swimming behaviour in the world´s warmest twilight zone

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  • Session: 09. New frontiers in fisheries acoustics: applications- analysis- decision and management tools
    Organiser(s): Victor Espinosa
  • Lecture: Individual daytime swimming behaviour in the world´s warmest twilight zone
    Paper ID: 2073
    Author(s): Sobradillo Bea, Christiansen Svenja, Rostad Anders, Kaartvedt Stein
    Presenter: Sobradillo Bea
    Abstract: We assessed the activity and swimming patterns of mesopelagic fishes in the Red Sea using bottom-moored, upward-facing echosounders deployed at 555 and 700 m depth. The vertically migrating mesopelagic scattering layer descended close to the bottom during daytime. This permitted assessment of behavior at mesopelagic depths by applying acoustic target tracking for individuals traversing the acoustic beam. Swimming activity did not fit the notion of torpid behavior in the daytime habitat. The fishes were moving continuously, with a prevailing downward direction before noon and upward after, though individuals were swimming in both directions at all times. They moreover were swimming horizontally at estimated speeds of ~2.1 cm s 1, suggesting ~0.5–1 body length s 1, intermittently turning. High activity at high temperatures suggests high respiration at depth, considered a key element for the active carbon pump.
  • Corresponding author: Dr Bea Sobradillo
    Affiliation: AZTI
    Country: Spain
    e-mail:

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