1National Research Institute of Fisheries Engineering, Hasaki, Ibaraki 314-0421, 2Department of Ocean Science and Technology, 3Department of Marine Science and Technology, Tokyo University of Fisheries, Minato, Tokyo 108-8477, Japan
The cross sectional pattern of the underwater illuminance for the coastal squid jigging boat was calculated with a formula based on the line light source model which consists of the spatial luminous distribution of fishing lamp and the surface reflectance of light by Fresnel's law. The calculated pattern of the contour map of the cross sectional underwater illuminance fits with the observed pattern under the coastal squid jigging boat equipped with the total light output of 150kW, 200kW and 240kW respectively, by considering the decreasing factor of luminous flux for fishing lamps due to their time of use.