Bull. Jpn. Soc. Fish. Oceanogr. 80(2), Page 115-123, 2016   A quick method for estimating egg density in sample bottle from fishery stock survey Masatoshi Hasegawa1†, Toshihide Kitakado2, Shigehide Iwata2 and Eiji Tanaka2 1 Shizuoka Prefectural Institute of Fishery Izu Branch, 251-1 Shirahama, Shimoda, Shizuoka 415-0012, Japan 2 Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato, Tokyo 108-8477, Japan † E-mail: masatoshi1_hasegawa@pref.shizuoka.lg.jp A rapid assessment of surveys of egg production of a fishery stock, such as the Japanese anchovies Engraulis japonicus or Japanese sardines Sardinops melanostictus, is one of the information necessary for predicting of the daily catch in the local whitebait fishery. We proposed a sequential combined method that consists the method of Most Probable Number (MPN) and a direct-count in order to reduce the time required to obtain unbiased estimate of the egg densities of the samples. In the method, the mean of egg density is estimated by the MPN if the density is low, but is done by a combination of the MPN and the direct-count if it is high. Effectiveness of the method was evaluated by simulation using the survey data of the Japanese anchovy in Suruga Bay. The results showed that the method provides good estimates of the true mean saving the time. We discussed about the application of this method. Key words: egg production survey, most probable number, direct-count, maximum likelihood estimation, quick assessment