Abstract
The vertical migration and diel feeding periodicity of the skinnycheek lanternfish (Benthosema pterotum) were studied by use of a hull-mounted 38 kHz echo sounder, ROV-deployments and net-sampling at two locations (similar to 24 degrees 48'N, similar to 36 degrees 15'E and similar to 21 degrees 27'N, similar to 38 degrees 5'E) in the central Red Sea. The mesopelagic zone of the Red Sea represents an unusual environment with very high temperatures (similar to 22 degrees C) and low zooplankton concentrations (< 10 individuals m(-3) below 600 m). The skinnycheek lanternfish performed normal diel vertical migration from similar to 500 to 750 m during daytime to the epipelagic zone (upper similar to 200 m) at night. A strict feeding periodicity occurred; with the skinnycheek lanternfish foraging on zooplankton throughout the night, while rapidly digesting the preceding nocturnal meal in the warm mesopelagic region. We hypothesize that the constrained epipelagic distribution of zooplankton and the unusual warm waters of the Red Sea force the whole population to ascend and feed in epipelagic waters every night, as the prey-ration eaten each night is fully digested at mesopelagic depths during daytime. (c) 2012 Elsevier Ltd. All rights reserved.