Daily catch data of coastal squid jigging boats, their light source output for fishing lamps and monthly mean wholesale prices of squid were collected from five fishing ports (Hakodate, Sado Island, Noto, Sakaiminato, and Tsushima) in Japan, for a purpose of evaluating optimum light source output, which created a maximum economic yield. The daily income were estimated from the relationship between daily catch data and monthly mean wholesale prices of squid. Then, the optimum light source output was calculated from the relationship between daily income and daily lighting expenses by each fishing management conditions. The results show that daily income and daily lighting expenses were significantly increased as light source output for fishing lamps were increased. The lower light source output which obtained by each fishing management conditions was advantageous when lighting cost become more expensive or wholesale price become cheaper then ever.
