Abstract
Codend opening/closing MOHT （COC-MOHT） was developed by installing the codend frame with
five codend nets on the base of the MOHT （Matuda-Oozeki-Hu Trawl）. To investigate the diel vertical
migration and net avoidance of lantern fish, three oblique tows from 250 m and 450 m depths to the
surface and one horizontal tow at different towing speed of 4, 3 and 2 knots for each codend were
conducted using COC-MOHT in Sagami Bay on 16 October 2014 by training vessel Umitaka-Maru
belonging to Tokyo University of Marine Science and Technology. Samples were sorted into
Myctophidae, Cephalopoda, Euphausiidae, Sergestidae, and other fishes. Lantern fish was measured in
standard body length and classified into 5mm intervals. It was found from the result of three oblique
tows that lantern fish distributed in the two major depth zones: shallower than 150 m and deeper than
250 m at daytime, depending on the myctophid species. And after sunset, lantern fish migrated from the
deeper zone to the shallower zone. In the horizontal tow, Diaphius spp. with SL › 30 mm were less
caught at lower towing speed. A possible explanation is that net avoidance of the larger fish occurred
because they can generally swim faster.
